Anyway, hope you enjoy this site!

Well this is it, this is my guide on how to install a JDM Climate Control in a 4th gen USDM Prelude. I’ll try to cover all aspect of this install, what parts you need and how to hook them up. I won’t explain how to remove your consoles and stuff like that (not for now anyway), you should have a Helm handy at all time when working on your car. Also please note that I am not responsible if you blow up your car, get a fine for releasing freon in the atmosphere or any other injuries or whatever that could happen.

Table of Content:

• Parts
• Tools
• Disassembling
• Wiring
• Assembling
• Conclusion
• Resources

Parts

Here are the parts you’ll need to get a fully functional JDM Climate Control.

• Climate Control Unit w/harness (at least the connectors with a few inches of wire)
  Probably the best place to get these is on Ebay. Or try one of Prelude or Honda board, most of them have some kind of Classify ads section. If you can, try to get everything with the Climate Control Unit, because some parts are kinda hard to find by themselves, the air mix control motor is one of them and it’s almost the most important part of the system.
• Air Mix Control Motor
  This is under the blower unit. It’s pretty much one of the hardest part to get your hands on so if you’re buying a complete JDM Climate Control system, make sure that you get this part.
• In-car Temperature Sensor
  On the right of the Climate Control Unit, it’s a little square vent thing. In the JDM cars it’s also attached to a hose.
• Outside Air Temperature Sensor
  In front of the car, it’s in front of the radiator and all that stuff I think.
• Sunlight Sensor
  On top of the dash near the windshield, it’s a little square thing with a round in it.
• Evaporator Temperature Sensor
  This on is in the evaporator unit, where our A/C thermostat is.
• Heater Core Temperature Sensor
  The heater core temp sensor is at the bottom of the heater unit, right under the heater core.
• Blower Motor High Relay
  This relay is attached to the blower unit.
• Power Transistor
  This is on the blower unit, it’s what replaces the blower resistor on our cars.
• Heater Valve and Solenoid (Optional)
  This is under your hood, the heater valve is on the water hose that goes from the engine to the heater unit. Try to get the valve with the solenoid. Though I’m pretty sure you could use another solenoid and it would work.

For the sensors, you can get them from a 1st gen Acura CL. I’ve check and the resistance is the same on the CL sensors and the JDM Prelude sensors. These diagrams are from the 1997 Acura CL 2.2L Base on http://www.acuraautomotiveparts.com. The In-car Temperature Sensor is the No. 5 on this picture, the Outside Air Temperature Sensor is No. 4 and the Sunlight Sensor is No. 2. The Evaporator Sensor is No. 19 on this picture.

For the Power Transistor, I used one from a 1st gen Acura CL. It’s part number is 79330-SF1-941. For the Blower Motor High Relay I used a fog light relay and sub-harness for the Prelude but when I received it there was no sub-harness cause it has been discontinued. So you can probably find a relay that’ll work at a scrap yard or something so you have a connector with it. For the Air Mix Control Motor I tried one from an Accord but it doesn’t work very well, I only have full hot or full cold, nothing in between, so I’m ordering a JDM air mix motor, For the Heater Valve and Solenoid you could use the manual heater valve you already have in your car but I decided to get a JDM vacuum actuated heater valve to make my conversion more JDM style.

Tools

Well you’ll need a few tools to install the Climate Control. You’ll probably have most tools you’ll need if you’ve done any work on your car already.

• Helm manual
• Screw drivers (Flat and Philips head)
• Pliers (A few different pairs is a good idea)
• Wire cutters
• Soldering iron or wire crimper
• Set of sockets and wrenches (Other than the ordinary socket set you’ll need a 12mm deep socket and also different size extensions will help)

Disassembling

You’re gonna have to do a lot of disassembling. I’m not gonna go into details about how to disassemble all that stuff, you really should have a Helm before trying a project like this one.Since I did this spanned over a year because I didn’t have all the parts I needed and stuff, I disassembled and re-assembled this stuff a few times but for this write-up I’ll write it so that you can do it in a weekend or so.

Center console removal
First remove your front console where the shifter is, then remove the center panel where the stereo and cig lighter is. Now you can remove the heater control panel and center air vent. It should now look like this.

Dash removal
Now remove the glove box, the dashboard lower cover, the knee bolster, the tweeter covers, the visor trim panel and the display visor. Remove the 2 screws under the steering wheel, and disconnect the air bag and connect the red connector. Remove the steering column covers and the air duck under the steering column. You can now remove the 2 nuts and 2 bolts that hold the steering and steering column in place and lower the steering on the floor. If you have a passenger side airbag disconnect it and put the red connector on it. Disconnect the 3 connectors on the driver side near the fusebox and the 2 connectors on the passenger side. You can now remove the 6 bolts and remove the dash. Be careful when you get it out of the car so you don’t hit anything, I knocked down my rear view mirror the first time I removed the dash.

Evaporator removal (A/C equipped cars)
With the dash out of the way, removing the evaporator is quite easy. First make sure you get your A/C system emptied by a professional. Releasing Freon in the atmosphere is illegal and you might be able to get a few bucks if you have a 92 with R-12 in it. Now there’s 1 nut and 1 bolt you need to remove under the hood, then there’s 5 bolts and 2 nuts inside the car. Disconnect the A/C thermostat and you can pull the evaporator out. Be careful when you pull the evaporator out not to break the pipes, there’s one that you’ll have to lift up a bit to be able to pull the evaporator.

Here’s one of the bolt for the evaporator under the hood.

And that’s the second bolt for the evaporator under the hood.

The evaporator is removed.

Heater duct removal (Cars without A/C)
Just remove the 4 bolts and remove out of the way.

Blower unit removal
Disconnect the 3 connectors from the blower unit. One’s in the from on the blower resistor, the other one on the left side on the recirculation control motor and the 3rd one is under the unit on the blower motor. Now there’s 2 bolts and 1 nut to remove and pull out of the way.

Heater unit removal
This one is more tricky, first you’ll need to drain the coolant. Then you’ll need to remove the intake tube and a few brackets on the firewall. You should remove the bracket holding the MAP sensor and the one under it. Disconnect the heater valve cable from the heater valve and disconnect the 2 coolant hoses that go through the firewall to the heater core. Those 2 hoses can be really hard to remove, so I suggest you do like I did, get some new ones and cut the old one off. They’re not expensive so it’s worth replacing them to save the trouble. Now a bit below where the hoses where connected and a few inches to each side, there are 2 bolts that pass through the firewall with nuts on them. You’ll need a 12mm deep socket to remove them. Remove them, then you can remove the 2 bolts inside the car on top of the heater unit. The one on the driver side is gonna be a bit harder because it’s kinda hidden. Now you can pull the heater unit but be careful because there’s still coolant inside the heater core and it might spill in your car.

Wiring

Before you begin, to make things easier, don’t cut your old connector right off before you start. Cut the wires one by one as you need to cut them to connect another wire to it, that’ll save you some trouble as some wires are the same colors.

Powering the unit
Now some wiring, let’s start by turning this thing on. When I’ll talk about the USDM connector it’s the one with 16 pins not the one with the 5 big wires. First connect the No. 8 (BLK/YEL) wire from the UDSM connector to the No. 13 (BLK/YEL) wire on the 20 pin JDM connector. Next connect the ground. There are 2 grounds on the JDM unit, there’s the No. 10 (BLK) wire on the 16 pin JDM connector and the No. 16 (BLK) wire on the 20 pin JDM connector. Connect those 2 wires to the No. 13 (BLK) wire on the USDM connector.

At this point the unit should turn on, I didn’t actually tried it at that point, I had a few more wires connected. You’ll have to press some buttons on it to actually see something on the display. When we’ll connect the memory you won’t have to do that everytime you start the car.

Memory
Hook up the wire No. 11 (WHT/YEL) on the JDM 20 pin connector to any wire that always have power to it, even when the car is stop, just like the memory wire on your stereo. You can hook it there if you want, that’s where mine is hooked up.

Combination Light Switch
Now some basic functions, connect the No. 6 (RED/BLK) wire from the USDM connector to the No. 2 (RED/BLK) wire on the 16 pin JDM connector. This is what dims your Climate Control when you turn on the headlight.

Rear window defroster
For the rear window defroster you connect the No. 10 (YEL/WHT) wire from the USDM connector to the No. 14 (YEL/GRN) wire on the JDM 16 pin connector.

Mode Control Motor
For now the unit doesn’t do much yet, other than looking cool and turning on the rear window defroster. So let’s make it more functional. We’ll connect the Mode Control Motor to control in which vent the air goes to.
There are 6 wires to connect for this and it’s pretty much just cut wire and splice it to the new connector.

• The No. 3 (BRN/WHT) wire from the USDM connector goes to the No. 6 (BRN/WHT) wire on the 16 pin JDM connector
• The No. 7 (LT GRN/WHT) wire on the USDM connector goes to the No. 15 (LT GRN/WHT) wire on the JDM 16 pin connector
• The No. 9 (LT GRN/RED) wire on the USDM connector goes to the No. 15 (LT GRN/RED) wire on the JDM 20 pin connector
• The No. 14 (BLU) wire on the USDM connector goes to the No. 7 (BLU) wire on the JDM 16 pin connector
• The No. 15 (BLU/RED) wire on the USDM connector goes to the No. 8 (BLU/RED) wire on the JDM 16 pin connector
• The No. 16 (YEL/GRN) wire on the USDM connector goes to the No. 16 (YEL/GRN) wire on the JDM 16 pin connector

Recirculation Control Motor
Now we’ll hook up the Recirculation Control Motor, there are 2 wires to connect for this. Just like the mode control motor it’s pretty much cut and splice back.

• The No. 4 (GRN/RED) wire from the USDM connector goes to the No. 13 (GRN/RED) wire on the 16 pin JDM connector
• The No. 11 (GRN/WHT) wire from the USDM connector goes to the No. 5 (GRN/WHT) wire on the 16 pin JDM connector

Blower Motor
Well now that you can control where to blow the air and choose if you want the air from inside or outside of the car, it might be a good idea to actually blow that air out now. There is a bit of wiring to do in order to control the blower. First take a look at this diagram I made. Just in case my diagram isn’t clear enough, the square thing on the left is the power transistor and the other one is the blower motor high relay. All wires on this diagrams are wires you will have to add. The dots on the diagram is where the wires are connected together in the diagram and the numbers are where you’ll connect the end of those wires to your car’s wiring and JDM Climate Control. The power transistor is what replaces the blower resistors on the blower unit.

Here’s what you have to do now

• Cut the BLU/RED wire that’s connected to the blower motor, you’ll have to connect it to the #1 wire on the diagram.
• You will have to splice a wire that comes from the No. 9 fuse in the Under Dash fusebox and connect it to the #2 wire on the diagram. There are plenty of places to splice that wire. I would recommend to use the BLK/YEL wire that connects to the recirculation control motor and attach your relay near the blower unit (that’s where the relay is in the JDMs).
• Now connect a wire to the #3 wire on the diagram and to the No. 1 (BLU/RED) wire on the JDM 16 pin connector.
• Connect the #4 wire on the diagram to the No. 3 (BLU/ORN) wire on the JDM 20 pin connector.
• Connect the #5 wire on the diagram to the No. 9 (WHT/BLU) wire on the JDM 16 pin connector.
• And the last but not least #6 wire is connected to a ground anywhere you want.

The transistor can be a little tricky, you have 3 pins on it, look at it this way, the pin that’s alone is the top pin, that’s the pin you’ll have to hook the #1 wire on. The pin on the right is the ground. The left one is the wire that goes to the No. 9 (WHT/BLU) wire on the JDM 16 pin connector. Since the BLU/RED wire is quite big compared to the other wires, you should probably use a wire that’s about the same size from the BLU/RED wire to the power transistor. Also you should probably use a wire that size for the ground wire from the power transistor. You should also use big wire for the BLU/RED wire from the splice between the blower motor and power transistor to the blower motor high relay and from the blower motor high relay to ground. For the other wires, I used the same size used almost everywhere.

You should make sure all those wires are connected properly before turning the unit back on. Also make sure you put the power transistor where the blower resistor is in the blower unit because some people blew up their power transistor because it overheated.

Air mix motor
The air mix motor’s wiring is pretty easy.

• The RED/YEL wire goes to the pin No. 4 on the JDM 16 pin connector.
• The RED/WHT wire goes to the pin No. 12 on the JDM 16 pin connector.
• The GRY wire goes to the pin No. 7 on the JDM 20 pin connector.
• The PNK/BLK wire goes to the pin No. 8 on the JDM 20 pin connector.
• The LT GRN/RED goes to a common ground point with the sensors to pin No. 17 on the JDM 20 pin connector.

Sensors

• The BRN/RED wire on the In-car temperature sensor goes to pin No. 18 on the JDM 20 pin connector.
• The BRN wire on the Evaporator temperature sensor goes to pin No. 9 on the JDM 20 pin connector.
• The BRN/WHT wire on the Outside Air temperature sensor goes to pin No. 19 on the JDM 20 pin connector.
• The WHT/RED wire on the Sunlight sensor goes to pin No. 10 on the JDM 20 pin connector.
• The PNK wire on the Heater core temperature sensor goes to pin No. 20 on the JDM 20 pin connector.
• All LT GRN/RED wires goes to a common ground point shared with the air mix motor on pin No. 17 on the JDM 20 pin connector.

Vehicle Speed Sensor (VSS)
The No. 5 (ORN) wire from the JDM 20 pin connector should be connected to the VSS wire (ORN) in the car. You can connect it to the ORN wire for the VSS at the ECU. (***** Note to self: Get actual ECU pin for VSS, someone remind me if I forget *****)

A/C
The No. 1 (BLU/RED) wire from the USDM connector goes to the No. 1 (BLU/YEL) wire on the 20 pin JDM connector

Water valve solenoid
The BRN/BLK wire on the solenoid should be hooked up the the No. 2 (BRN/BLK) wire on the 20 pin JDM connector. The BLK/YEL wire on the solenoid should be spliced on the BLK/YEL wire that goes to the No. 13 (BLK/YEL) pin of the 20 pin JDM connector or to the BLK/YEL wire that goes to the mode control motor or the recirculation control motor since they are all linked together.

Assembling

Air mix motor
The air mix motor can be a bit complicated to install. If you look at the first picture below, the air mix motor should be in the bottom right corner. In the second and third picture, you can see that the bracket in the JDM cars is almost the same as the USDM bracket except that it’s a mirrored copy and instead of a place to connect a cable it’s a hole to connect a wire. The problem with the stock location of the air mix motor is this, it’s made for a right hand drive car so if you try to mount it like it’s mounted on JDM cars, it’s gonna work the opposite way. (32 is gonna blow cold air and 18 hot air).

There are a few options to make it work right.

At first I wanted to find a way to mount it in the original location, though if I wanted it to work to right way I would’ve had to find a way to reverse it. Easier said than done, reversing the hot and cold wire won’t work since the motor is gonna send the wrong signal to the unit to tell where it’s at. I opened up my air mix motor to see what could be done about it. As you can see in the pictures below, reversing the motor would’ve require modification to the PCB or maybe even a new PCB that would work the opposite way than the current one. Since I didn’t want to be without a car for a month, I decided to go to Plan B.

This is what is looks like without the cover.

Here I removed the top gear.

The motor under the PCB.

So what’s Plan B? Plan B was to find a way to get the air mix motor to work the right way without modifying it. How do you do that? Flip it upside down. The only thing is that you won’t be able to mount it in the stock location, so finding another place to mount it is required. Look at the picture below to see how I mounted mine.

Air mix motor mounted to the heater unit.

Checking for clearance in the car.

Ready to go back in the car.

Mounting it this way requires you to take the heater unit apart, take away a bit of plastic that’s in the way, drill some holes, put some spacer under the motor bracket and bolt it in place. I used 2 nuts about 3/8″ high for the spacer. You’ll need a wire to open and close the flaps on the heater so get one the right size and cut and bent where needed. You’ll also need some kind of clip or something to connect it to the heater mechanism. Make sure that you set the air mix motor either to full hot or full cold and fully open or close the flaps on the heater depending on either it’s full hot or cold when you cut/bent the wire.

Power transistor/Blower motor high relay
The power transistor should go where the blower resistor was and for the blower motor high relay, I just attached it with the bottom screw of the recirculation motor.

Sensors
The In-car temperature sensor goes in the dash between the unit and the steering wheels. You’ll need to cut a hole in the dash. The tube from the sensor should go to the bottom of the heater unit. You will need to make a hole for it at the bottom of the heater unit near the mode control motor. For the sunlight sensor, you’ll also need to make a hole in the dash but close to the windshield, I made mine on the passenger side a bit but it doesn’t really matter where as long as it’s close to the windshield. The evaporator sensor goes in the evaporator where the A/C thermostat was. You might need to enlarge the hole in the rubber grommet. The Outside air temperature sensor goes outside to the front of the car, just find a place to mount it near the bumper. The heater core temperature sensor goes underneath the heater core. You will need to make a hole on the heater unit under the heater core. Make sure you don’t make a hole in the heater core or you’ll end up with a big mess of coolant in your car.

Hole in the heater unit

Hose connected to the unit

Heater core temperature sensor installed

Water valve and solenoid
The water valve just replaces the current water valve in the car on the firewall. It’s attached with one bolt. You’ll need to find a place to mount your solenoid though. And the small vacuum hoses should be hooked up like in this picture with the hose that’s not connected going to the intake manifold if you have a place to connect it. If you don’t have any place left to connect it, you might need to get a T to splice one of the vacuum hose to connect it.

Re-assembling the car
Now re-install your heater unit, blower unit, evaporator, dash and everything else and you should be done! Just make sure you test if everything works before re-installing the dash cause it’s not fun to remove and re-install the dash all the time. Also note that you might need to cut a small notch in the center console to clear the air mix control motor.

Conclusion

Well this is it, the install is finished. I only need to re-fill my A/C system but other than no A/C everything is working great. I hope I haven’t forgot anything but if you think I forgot something, let me know. If you have any questions or comments drop me an e-mail at jrc@jrcormier.com

Hope you guys enjoy your fully functional JDM Climate Control!

Resources

• My official thread about the JDM Climate Control on PreludeOnline.com
• JDM Climate Control Wiring Diagram - Part 1
• JDM Climate Control Wiring Diagram - Part 2
• JDM Climate Control Pinout

Updates:

• I’ve used the H23 PS pump for a few years but then it started to get noisy a bit, what happened is when using the H23 pump and bracket, the belt isn’t in a perfect straight line between the pump pulley and the crank pulley, so my guess is it started to wear out the bearing in the pump. I’ve bought a used 4th gen VTEC PS pump and now the noise is gone.

Here’s the engine in the van when we got it. My father has a Chevrolet Astro van extended version so there was enough space in the back without removing the back seats but we didn’t knew there was 2 big boxes coming along with that engine but we still had enough place.

Here’s some pics of the engine:

Time for some last pictures of that engine before we start taking everything apart.

On this picture you can see Marcel, the school’s mechanic teacher on the left and my father on the right. Having someone who knows how to work on a car helps a lot and saves a lot of time.

Now remove the hood to have more space to work and unplug the battery. Now raise the car and remove both front wheels. If you have access to a hoist you are lucky, if not a pair of jack stands could probably do. Then remove the brakes (but don’t unplug the hoses or you’ll need to bleed them) and attach them with some wire or something to the coil springs.

Now remove the hub nuts, if you got a big 3/4″ ratchet or breaker bar it shouldn’t be a problem, otherwise just use a 1/2″ breaker bar with an extension (metal pipe) it shouldn’t be too hard, just put 2 wheels nut to protect the thread and put a pry bar in between and have someone hold it to the ground so it can stop the wheel from rotating. Don’t forget to bend the locking tab out on the hub nut before you try to remove it though.

Now is a good time to drain the oil, tranny oil, coolant, PS fluid and clutch fluid. We only drained the coolant and tranny oil, but you should drain the PS and clutch fluid, you’ll know why later.

Now loosen the lower ball joint nut, this one is hard to get loosen, we broke a socket trying to loosen it. Then you’ll need to separate the lower arm from the ball joint, we used a puller to separate them. Then remove the bolt attaching the damper fork to the lower arm. Lift the hub/disk out of the way and remove the drive shaft by prying them out. Do not pull on the shaft cause you’ll separate the CV joint. That’s what they did to the CV joint I got with my engine so I had to re-use my old ones, the new ones are still good but I’ll need to replaces the boots and put the shaft back in the CV joint. After you removed the drive shaft, put the lower arm bolt and lower ball joint nut back in place so you don’t loose them. Don’t tighten them unless you like giving yourself a hard time.

Now start removing stuff that’ll be in your way, battery, air filter, air duck, radiator, etc. You might need to label some hoses you remove so you know where to connect them afterwards. We did label most of the little hoses that we might not know where to connect but I found a Helm vacuum diagram to be even better than labeling that. The blue hose on this picture connected to the A/C like is a A/C fluid pump or whatever what they are called. It helps to have an uncle who repairs refrigerators. So after the A/C has been drained we can remove the A/C pipes. There are 2 smalls hoses coming out of the speed sensor on the 4th gens tranny, it’s on the back of the tranny you can barely see them. If you drained the PS fluid you can remove them without worrying about making a mess. We didn’t drain the PS fluid so when we removed the hoses it started to get out of there so we just put plugs over it. We didn’t drain the clutch fluid either, so we spilled a little on the floor and there might be some still in the pipes. But nevertheless we’ll still have to bleed it. Also don’t forget the tranny cables.

Now remove the header downpipe from the exhaust manifold, there are 3 nuts and they are probably tight so it helps to have a torch to cut them out. Then remove the 2 bolts on the bracket on the header downpipe behind the engine, you’ll have to get them from under the car. And disconnect the O2 sensor while you’re there.

Now with an engine hoist attach the engine with chains on the 2 hooks on near the PS pump and the other on the tranny. Lift until the chains are stretched and remove the engine mount bolts. Then start lifting the engine slowly to make sure everything is unplugged. We found it easier to unplug the 2 coolant line going to the heater unit when the engine was in the air a bit. And we forgot the sensor that’s connected to the PS line so we unplugged it at the same time. Make sure you don’t have anything else plugged before you lift the engine out completely. Now lift the engine high enough to clear the front of the car making sure nothing is connected to the engine. And pull it out of the way. A little trick is to put the chain slightly smaller on the driver side so you can lift that end first and get the tranny to pass under the mount. Also once the engine has clear the car, lower it to a few inches off the ground in case something happens it won’t fall from too high. And before you ask, yes I’m the guy with the blue/white shirt and no that’s not a shirt I wear all the time, I only put that shirt on to do dirty work like this.

It took us 6 hours to get to this point. But it feels so good to finally have the engine out of the car. Here’s a few pics of the engine and the empty engine bay. If you look carefully in the first pic you can see the 2 PS hoses plugged with a hose and bolts where there’s a big oil spot.

With both engine on the floor, you will need to swap a few things from one engine to the other. First, the vehicle speed sensor (VSS), as you can see on this picture they are different. The one on the right is the sensor from the H22A4 and the one on the left from the H23A1, notice the 2 hoses coming out of the one on the left. Those hoses are PS lines, they are used for the speed sensitive PS we have in the 4th gen, that’s what makes the steering stiffer as you get to higher speed. On the 5th gen the PS works differently, it uses the RPM instead of the speed. Also the gears on the sensors are different length but they have the same number of teeth and they look quite alike when you put both side by side and the sensors fits so theoretically it should work, but I can’t tell you for sure now since as I’m writing this the car hasn’t start with it’s new engine yet. I’ll put an update as soon as it starts.

One other thing you’ll need to swap is the fuel rail. The fuel rail has the gas line coming on the other side on the 5th gen so use your 4th gen fuel rail. The injectors on the 5th gen engines are saturated injectors and on the 4th gen they’re peak and hold injectors. The difference is that the saturated injectors have higher resistance and since the Honda ECUs need that high resistance you need either saturated injectors or peak and hold injectors with a resistor pack. What the resistor pack do is put more resistance in the injector’s wires to give them the same resistance as the saturated injectors. Cause the resistor pack is already wired on the 4th engine harness, it’s easier to use peak and hold injectors. You can either modify the wiring or use peak and hold injectors. And if you’re wondering why I said you need to either modify the wiring to use the 5th gen injectors, well that’s because you’ll also have to swap the engine harness while the engines are on the floor. I will explain more about this later. I used my H23A1 injectors so I don’t have to cut more wires on my harness. But since the H23A1 are 240cc and the H22A4 are 290cc, I’m thinking about getting a set of 4th gen VTEC injectors which are 330cc.

Now swap your engine harness, first remove them from both engines, and if possible put some masking tape with something written on it that’ll tell you where they go. Then put both harness on the floor or table or anything big enough so you can put them both side by side to compare them. Start with the main connectors, they’re not alike but that doesn’t matter. What matters is that those connectors will match the ones in the car, that’s why you’re using your old engine harness. After the main connectors, there’s some starter wires, some sensor right on top of the tranny and we get to the distributor connectors.

You will notice that one of the connector is the same but not the other one. That’s because on the 4th gen there’s a sensor in the distributor that’s not in the 5th gen distributor. So where is it? If you look on the back of your H22A4, there’s some wires going down the timing belt cover and entering in the engine. That’s the sensor. So here you have 2 choices, either use the distributor on the H23A1 and left the sensor on the timing belt cover unplugged or replace the connector on your H23A1 harness with the one on the H22A4 harness and lengthen the other wires to get to the sensor on the timing belt cover. I don’t know which wires goes where but I’ll try to find it and make and update for this too. I decided to swap the distributor but that’s for another reason that I’ll tell you later on. Also from what I’ve read, if you want to alter your timing you need to use the distributor from your H23A1 because the sensor on the timing belt cover won’t allow you to alter the timing. That’s what I’ve read, I have nothing to prove this myself but if you think about it, it makes sense since when you move the distributor you’ll move the sensor that’s in it too but you can’t move the sensor in the timing belt cover.

Also there’s some coolant temperature sensor that’s missing on the 5th gen the one connected to the upper radiator pipe connector on the engine. What we did here was swap the metal thing that connects the pipe to the engine from the H23 so you now have that sensor.

Now we get to the 2 sensors under the distributor, no problem there. After that there’s a little difference. You will notice the coil wire isn’t at the same place on both harness. That’s because the coil is a little more in the back on the H22A4 to clear the VTEC solenoid and oil pressure switch, so you will need to lengthen the coil wires. What we did was cut the coil wires on the H22A4 harness about 5-6″ away and replaced the H23A1 coil connector with it. The 2 connectors are identical so it’s not a problem.

The VTEC solenoid and oil pressure switch are something that’s not on the H23A1 so there’s no connector for them in the harness but some Prelude (even some 92 even though there’s no VTEC in 92 in America) are pre-wired for them already. But there’s no need to worry for this now, that’s one of the things you’ll do last.

Next there’s the exhaust gas recirculation (EGR) lift sensor. It’s right above the EGR valve, the little thing between the throttle body and coil. Also the manifold absolute pressure (MAP) sensor is directly on the throttle body on the H22A4, on the H23A1 it’s on the firewall behind the intake manifold. It’s a little thing with a connector and 2 small rubber hoses into it. We’ll deal with this later. Don’t forget to connect the speed sensor, we almost forgot that one. But that’s something I’ll talk about later. There’s also a ground around there.

After that, the next sensor is some sensor under the oil filter, you need a 7mm socket to get it out.

Now comes the O2 sensor. Since it’s on the header downpipe, don’t worry about it for now. I will talk more about it when we get to install the downpipe.

There are a few identical connectors here, remember I said to label the connectors as you remove them? First the knock sensor (that’s the one above the oil filter), the connectors aren’t the same on both engines, you might have 2 options here, one is to cut the connector a replace it with the one on the H22A4 harness, the other is to use the sensor on your H23A1. Since I broke the sensor on my H23A1 that left me with only one choice but this too I’ll explain why we used the first option.

The next connector is going in the intake air bypass (IAB) control solenoid valve, that’s the little black box under your intake manifold.

And there’s another connector at the end of the intake manifold behind the IAB control diaphragm.

Then there’s the sensor in the timing belt cover that we decided not to use, if you decide to use it then lengthen the wires that were in your old distributor and connect it. Again I don’t know which wires you need for this sensor but I’ll try to find it.

We’re almost done with the harness swapping, the rest of the connectors goes to the top or front of the engine. There’s a connector alone that seem to be farther away from the others that goes to the resistor pack. The resistor pack is the little thing that’s in the corner of your hood on the driver side near the windshield. It looks like a heat sink. Again here if you really want to use the injectors from your H22A4 you’ll have to find a way to bypass that. I think you could just cut the wire that goes to the resistor pack and connect the 4 black wire to the red one but don’t take my word for it I don’t have the wiring for the 5th gen. If you blow something up it’s not my fault, I told you to use your old injectors!!

Now there’s the wire cover that goes over the valve cover, you’ll can’t use the one from the H23A1 since the H22A4 valve cover isn’t the same size. Just cut the tape at each end and unclip it and remove the wire from it. Connect the alternator, if you got an alternator with your new engine then you have 2 options, either use your old alternator or cut the connector on the H22A4 harness and replace the one on the H23A1 harness with it. I decided to keep the new alternator. Now put the new wire cover over the wire once you know how much wire length you need on each side of the engine.

Now connect the injectors you can’t put them in the wrong place. If you do you don’t belong anywhere near a car with the hood open. If you decided to use the new injectors you’ll have to swap connectors with the other harness but since you all decided to use your old injectors cause they’re bigger, that won’t be a problem.

And finally connect the other connector that’s on the intake manifold behind the fuel rail. And we’re done with the harness swapping.

Last thing to swap is the 2 side mounts on the 4th gen the mounts on the chassis are welled to the car, on the 5th gen they’re bolted to it. Just swap the 2 side mounts and it’ll fit right in as if it was made for it.

You’re now ready to put your new engine in the car!!

Attach chains to the 2 hooks on the engine and lift it with the engine hoist. You’ll notice that we only used one chain and a strap. That’s because the easiest way to get the engine in the car is to have the tranny side of the engine lower than the belt side so the tranny clears the mount. But with the engine inclined like that you’ll have trouble with the front and rear mount, that’s why we used a strap there so that we can get the engine to it’s normal position after we cleared the tranny mount. On this picture my father and Marcel are trying to connect the 2 coolant hoses that goes in the heater. You should plug them before the engine in completely in. When mounting the engine, start with the tranny mount first, that’s the easiest one to install, then do driver side mount, then front and back.

You can now remove your chains or whatever you used to put the engine in. Plug all the hoses, connectors, fuel line, tranny cable, install the radiator, etc.

Now install the drive shafts, that shouldn’t be a problem since it’s easier to install them then removing them. Also you need to use 4th gen driveshafts here since 5th gens are a bit different in length.

Now for the exhaust manifold and header downpipe, if you can get something like a DC Sports or any other brand 93-96 Prelude VTEC header, that’s what I wanted to do but I didn’t find anybody who could get me one in time for the swap. So I thought I’d use the exhaust manifold that came with the H22A4 and the downpipe that I had on my H23A1, well they don’t fit together. And you can’t use the H23A1 exhaust manifold the bolt pattern isn’t the same. So all I could use was the full H22A4 header. The problem is that the downpipe is shorter than the one on the 4th gen so what cut the 4th gen downpipe about 3 inches from the flange on the cat converter and we welled some pipe on it and made a custom made torch cutted flange that would fit on the 5th gen header. It’ll be good enough for a while until I can afford a DC Sports and a full VTEC exhaust. A problem if you have a 93-96 Prelude VTEC header is that the flange don’t match the cat converter’s flange. But that’s nothing a torch and a mig welder can’t take care of. And also a VTEC exhaust’s flange won’t match the flange of the Si cat. converter. That’s why I want to get a full VTEC exhaust. So I won’t need custom stuff everytime my exhaust is busted. And it’s kinda time to change it anyway.

Remember I said you need to swap the engine harness? Well we didn’t knew that at first… So we still had the H22A4 harness on the engine when we put it in the car. And no you can’t just connect the main connectors of the H22A4 harness to the chassis harness. I search for wiring diagrams of the H22A4 harness but I didn’t have much luck. So we decided to swap the harness with the engine in the car (There was no way we were removing the engine again just to swap the harness). It took us 4 hours, how long would’ve it took if we had done it while the 2 engines were on the floor? About 30 minutes to 1h and it would’ve been way easier. So trust me on this one and swap your engine harness while the engine is out of the car. I’ve warned you!

Now that you know this it explains some stuff. You remember that sensor on the timing belt cover? Well we had enough trouble getting the harness there so I didn’t want to have the troubles of getting more wires there. That is also why we almost forget to connect the speed sensor, it’s almost hidden when the engine is in the car that it’s easy to forget. And for the knock sensor, when we compared the harnesses I didn’t notice that the connectors weren’t the same. So we had to cut the wires and replace the connector with the one from the H22A4 but it’s not fun doing that when you don’t have much play in the wires. Again I say that, swap your harness before you put the engine in!

Now that the header is installed, we can connect the O2 sensor. Well at first we had some problem with this. The connector on the H22A4 harness was the same gender as the one on the 4th gen O2 sensor that was on the 4th gen downpipe. But since we swap the downpipe to the 5th gen one they’re not the same gender anymore. But after that we also swapped the engine harness so now we have the 4th gen harness with the 5th gen O2 sensor so they’re still the same gender. So what we can do is either swap the O2 sensor and use the 4th gen one or cut the wires and swap the connectors. This will depend on either the wires are the same and we know which wire goes where. We decided to cut the connector on the 5th gen O2 sensor and plug it in the stock connector on the harness.

Well we’re almost finished with the swap, we got some problems with the PS pump, the pump I got with the new engine doesn’t use the same fitting as the old one and the PS line wouldn’t clear the head anyway. So we had 2 options use the old pump or get a 5th gen PS line and cut both line and get it crimped at some place that does hydraulic piping, but most place won’t do PS lines (well around here anyway, that’s what I’ve been told). We swapped the pump but the bracket isn’t exactly the same on the old one and you can’t screw the wire cover that goes over the valve cover on it.

Then we put oil in the tranny and engine, bleeded the clutch (don’t ask me how to do that I still have no idea), added coolant.

Then I swapped the ECU. You need to remove the plastic cover that’s on the right side of the floor in front of the door. Then pull the carpet and there’ll be some kind of rack you need to remove the nuts (there’s 6 I think), then remove the 4 ECU bolts. My car wasn’t wired for VTEC so I took an old connector that was similar to the ECU one and broke it and took some pins with a few inches of wire and added the pin to the ECU for pins A4 and D6. Then I passed some wire through the firewall, there’s a place for that under the fusebox, and I connected the VTEC solenoid to the A4 pin and the oil pressure switch to pin D6 and the other wire of the oil pressure switch should be wired to the ground on the thermostat housing.

Gentlemen start your engine!! If you did everything right and didn’t forget to plug anything it should start. Mine started the first time but I had to let it turn a few turn before it started.

Well the car now runs perfectly! I had some idling problems at first but it was because we forgot to connect a hose on the intake manifold.