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H22/23 or B16/18/20n-z swap with AC conversion

General '88 - '91 Prelude Discussion
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1funryd United States of America
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H22/23 or B16/18/20n-z swap with AC conversion

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Post by 1funryd » 01 Nov 2018, 05:55

I have finally completed the AC conversion for the H22/23 swaps. This is for those who want to go with the OEM AC compressor for the H motors. It is actually easier than we initially thought and has been done and running in my H23 swap. Read below and enjoy!!!

Ok let me explain it.




1. You need to bypass Clutch Relay B under the Battery try, there are two relays. Relay B has the solid colored wires so to do this you need too:
  • Cut the Red wire and Grey wire on Relay B Butt connect them together with insulated butt connectors to be heat shrank by heat gun. For weather proofing. You have now bypassed Relay B.
  • Cut the Yellow/Blck wire on Relay A side wiring, this wire is a hot wire that needs to be connected to a 12v ignition switched connection or just run a jumper wire straight to the ignition harness under the dash in front of the fuse panel on the drivers left leg side. I just ran the jumper wire along the front of the battery along the side of the engine bay fuse panel zip tied it to the high pressure ac line that is there and the behind the Vaccum box along the fire wall and into the rubber gromet that is right behind the gas pedal and straight to the fuse panel and plugged it there.
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  • The 1st accessory wire is the fat Yellow/Blck wire on the ignition wiring. There is no need to undo the dash this wire runs along the bottom of the fuse panel coming from the ignition. But if you need wiggle room then go ahead and drop the under dash panel. Tap that wire with those female electrical T-tap connectors, you will need the yellow T-taps on this wire because it is a thick guage wire.
  • Next we are going to connect all the hot wires together since they all need the 12v ignition switched power source. Cut the Red/Yellow wire on Relay A as well, then splice Yellow/Blck and the Red/Yellow together so they are all connected because they will be supplied by the same jumper wire to the 12v switched source.
  • When you butt connect all these wires together please get the insulated heat shrink butt connectors so they are weather proofed, you are not going to want to mess with these wires again.
2. Next we move on to the AC Compressor wiring.
  • First cut the harness off of the original B20/21 compressor, this is crucial because it already contains the diode that is going to be needed to reduce the electrical back surge to protect the ac clutch relay.
  • Cut as close to the compressor as possible, leave about at least 2" left at the compressor for possible reconnection later should you choose to.
  • The harness from the compressor will have a Red and Brown wire, and a Green and White wire, then the one wire left which is the Diode wiring. Connect the Red and Brown wire together, then cut the Green and White wire as close to the harness as possible and electrical tape it up, it is not going to be used.
  • The diode wire will have a connector on it you will want to cut off the the bullet style male connector and connect it to the one single Red hot wire on the H22/23 compressor. This will keep the Diode inline of the hot wire on the H compressor.
  • Clean it all up and make sure everything is nice and taped up and insulated.
3. Now to move on to the ECU side. The H22/23 ECU's control the AC clutch, and Condensor Fans and the throttle response for adding fuel to the system once the compressor kicks on so that it does not stall.
  • First take off the glove box, and unplugg the CCU unit, it was the control module that everyone always needed to resolder due to corroded solder points and the weak link in the OEM AC system.
  • Now cut the Red/Blue and Red/Yellow wires behind the harness plug and butt connect them together, and that will bypass the AC Control box or otherwise known as the CCU unit.
  • Now you leave the plug unplugged from the CCU box, you have now elimitated the CCU unit. It will no longer be needed.


Here is picture of the CCU unit location....(borrowed someone elses pic..)
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You are now electrically ready to pluge it all up and turn it all on. I recommend you do not tape everything back up until you have tested your connections, or else you will have to take all apart again.


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You will need to get custom AC lines made to route the lines properly to clear the motor should you need to pull the motor at a later date. Once make those lines and vaccum the system and the refill it, it will cost you alot of money to refill it again should you pull the lines back off if you need to pull the motor out. So keep that in mind when having them made.

And make sure you have enough of the tubing coming out of the ac compressor so your local AC shop can have enough material to work with or they will charge you more for adding and welding in more aluminum ac tubing.

Here is a picture of how my lines are run. I will be redoing the low pressure side which runs along and over the tranny.


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Enjoy and happy luding!!!!:-P

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