Dealer installed AC harnesses info

[pizzaman09]

My truck has dealer installed AC.  A forum member asked for how it was routed and where everything hooked up.  I decided to post this for reference to anyone that might be trying to add AC.

 

I took photos of the entire engine side harness. I started at the temp sensor and ended at the compressor.

 

 

 

You can actually see two temp sensors in the photo below, the dealer spliced into the lower radiator hose and put the sensor in that has the black braided wire covering. This was done because stock radiators without AC didn't come with a threaded port for this. As my Comanche had a newer radiator with the port I put in the other sensor which is now crusty green and has the red wire. Both are valid approaches.

 

Another wire from that end of the harness goes to the electric fan.

 

The harness was routed under the front of the air box to run near the driver's side of the engine bay. It's the corrugated plastic covered line I pulled up beside the air box here. 

 

Near the back of the air box there is a relay plugged in.

 

Detailed photo of said relay.

86 Yellow wire

87 Red and Red w/ black tracer

85 Both black wires

30 Gray w/ black tracer and Orange 

87a no wires connected

 

The yellow and gray w/ black tracer wires goto to the radiator temp sensor.

 

One of the black and the orange wires goto the electric fan

 

Right near this relay is where the dealer AC harnesses plugs into the truck harness. The truck harness is the big bundle of wires that runs over the drivers wheel well. Looks like it is grounded at the fender here too.

 

The part of the harness that goes to the other side of the engine bay is routed around the brake booster.

 

Up across the cowl, one zip tie held it to a wire harness it crosses.

 

It runs across the top of the rear of the valve cover and routes down right under the left edge of the expansion tank between the heater core hose and the bottom expansion tank hose it's the wire harness that has crusty yellow coolant on it under the expansion tank.

 

It then routes near the relays that are behind the ignition coil.

 

Right in the center of this picture the harness splits off two ways, one section goes down to the relay that is how in the next picture, the second leg goes across the ignition coil output over to the compressor and pressure switch.

 

The Bosch relay I just mentioned is mounted to the left of the other relays on the relay bar.

 

You can see the wire that goes over the ignition coil splits and one connector goes to the pressure switch and the other goes up the back of the compressor.

 

The compressor wires come up between the high and low ports and connect to the front of the compressor.

[NickyV]

That was me! I am in the middle of putting A/C in my 1987 MJ. It's a 2.5L, 4-speed manual (AX-4). My plan is to figure out a way to also add an electric fan.

 

My truck never had A/C, and the 2.5Ls never had an electric fan at all -- but I think this is possible.

 

Every step along the way I've thought to myself: "This is gotta be the hardest part."

 

Finding the right brackets: "This has got to be the hardest part."

 

Refurbishing the HVAC box: "This has got to be the hardest part."

 

Figuring out where to get hoses that no one stocks anymore: "This has got to be the hardest part."

 

But let me tell you all... at least for me, figuring out how to reverse-engineer the "Dealer" side of the Dealer-Installed Electrical Harness... man this has been a journey.

 

I have cross-referenced so many different manuals -- Parts Manual, Electrical Troubleshooting, the wiring section in the FSM and Haynes manual. I've sent several of you private messages. I am now working on modeling what I think the circuit is using graphing paper and a free online tool called Tinkercad.

 

Tinkercad (www.tinkercad.com) is designed for microcontroller stuff, so it isn't perfect... But I do think I am pretty close to figuring this out. I plan to post about my findings once I get everything working.

 

Thanks to all of you who have been patient with me and answered my questions!

[AnotherOldJeepGuy]

Sounds like quite a challenge, good luck!  Will be interesting to see how it turns out.  I may have to try my hand at tindercad...

[NickyV]

Well, if you want to give Tinkercad a try, I'd recommend it. I think it's pretty easy to use, especially if you use ChatGPT or some other AI to ask questions about how to use it.

 

If anyone decides to try it out, you can view my circuit here: https://www.tinkercad.com/things/gHNlViVpPVx-ac-fan-circuit-mj?sharecode=0m3G24SuONVXhRhFX79NZaLWc-r2XZxn2XKiO1nP4TQ