Adding 94-96 XJ A/C to 87-90 MJ - Slow Thread

[Gojira94]

It's going to take a while to gather everything I'll need to do this. I'm guessing it'll take 6-9 months to gather it all and be ready to do the install. I've chosen to do a hybrid setup, using Renix-era inside parts, aside from the evaporator itself. Under the hood, I'm opting for a 94-96 R134a native setup. I don't like the 97-01 setup that uses stamped metal clips to hold the lines together at the condenser, no thanks. And 87-90 to me looks cluttered and the hoses and parts are hard to come by from what I've seen in discussions here.

 

My engine control harness is from 1989 or 1990 and it has the pins for A/C. My engine harness is from something else and does not have the diode module, A/C clutch relay, clutch feed or pressure switch connectors. I can make all that from parts cut from an 87-90 in the boneyard, or buy the whole harness at the boneyard for about $60 and recondition it.

 

I have the 91-98 compressor mounting bracket, my alternator is sitting on it right now. I'll have to move the alternator down to the original HO location and get a pair of HO alt mounting brackets and shave them for my Durango unit. And a new belt.

 

The remaining parts needed are as follows:

 

HVAC Housing - 87-96 boneyard rehab

Temperature Control Panel for A/C equipped car - 87-96 boneyard rehab

A/C Dash Harness - 87-90 boneyard rehab

A/C Thermostat Control Switch on HVAC box - 87-90 boneyard grab or new Crown 56002688 from Quadratec.com 

Evaporator - new 1994-96

Evaporator drain tube - 87-96 boneyard rehab

Expansion Valve - new 1994-96

Low Pressure Cutoff Switch on drier - new 1994-96

Receiver drier - new 1994-96

Compressor to condenser hose - new 1994-96

Low Side TxV to compressor hose - new 1994-96

Condenser to drier hose - new 1994-96

Drier to evaporator hose - unobtanium, acquire a used 1994-96 and have it re-made new UAC HA-111291C for 94-96

Compressor - new 1994-96

Condenser - new 1994-96

Condenser to radiator mounting tabs - 87-96 boneyard rehab + new hardware for them

 

I'm going nuts right now because I have a source vehicle located for some of the big items. But there's no way I can get to it until the weekend of August 8th-9th 2026!

[Gojira94]

First update - the trip to the boneyard was a success.

 

Heater housing bare - $22.50

Temperature control - $36.00

Wiring harness engine - $ 55.50

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Bonus items:

 

Engine control module - $82.00

Shifter bezel - $14.00

 

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$225.20 with 7% tax...

 

 

Computer is a 56006078 - According to an old post by @HOrnbrod, it is "Renix ECU 56006078 is an alternate (superseded) part number for ECU 53005406."

Mini console has unbroken mounting tabs, so I grabbed it.

 

 

I thought I was smart for going for a 1990/ last year of Renix engine harness. However, this was when Chrysler was starting to dig its fingers into stuff and they unified what would have been 'Engine to Alternator' C105 & C335 on 87-89 88 into this, below (EDIT - 1989 also has these connectors, so C105 and C335 unified into the grey Chrysler connector was either a mid-year 1989 change, or covers all of 1989 MY production):

 

 

They also made a change and unified what would have been C103 (6-way) & C109 (4-way) on 87-89 into this 10-way, below:

 

 

They left C104 alone (10-way). There is also this connector I haven't figured out yet. Where it went was low on the passenger side into a really dirty area I wasn't in the mood to dig into since I was about to tear into the dash. 3-way mystery connector below:

 

 

My verdict is that I'm going to harvest what I need from this harness, rather than trying to use it complete. Yes, I could go get connectors from an 87-88 and convert back the changed Chrysler connectors. However, I can't be 100% sure C100 is the same as what I have now on a 1989 non-A/C-equipped engine harness. For me it's no big deal to splice in the fan diode and A/C Clutch Relay and the C100 pins G5, H1, H4 if needed for A/C Request & A/C Select. I've already cleaned up, gone through, and made the modifications for electric fan and fog lights on the harness I already have, and everything else works well the way it is. Better the devil you know than the one you don't. I do already have a (now 100% confirmed) 1989 Engine Control Harness that does have A/C provisions, that came with the project from the beginning, and it's perfect. And it also explains why my trans harness pass-through connector at the ECU connectors from its reverse lights connector is different from the 87-88. And I had to cobble the 2 together to get reverse lights working a while back.

 

Next up is to clean and prep the heater housing. The temptation is to get an evaporator ready in it and when the cool days come back to NC, swap it out with my heater core in it and be done with the cab side of the swap.

 

Edited 18 hours ago by Gojira94
Updated info

[Gojira94]

I went back to the boneyard to a 1988 XJ and got the missing pin C / orange wire for C109. I also got the fan diode with radiator temp switch connector attached for my visual reference. And the A/C Clutch Relay socket/ pigtail.

 

I'd decided against cutting into the 1990 engine harness. I'm going to clean it up a bit, do a few minor repairs around the EGR & ballast resistor connections and offer it up to anyone who might need it/ want it for an 89 or 90 rig. I paid $59.50 for it, so  +$20 and shipping cost and it's yours. PM me if interested.

 

I also ordered a 1996 evaporator and started cleaning up the 1990 HVAC housing. I can see that very slight modification will be needed. The height is over by about 1/4" from perfect. Front to back fitment is good-ish but I'm going to massage the back/ cab-facing lower portion of the box to gain about another 1/4" front-back clearance and settle the rear of the evaporator down about 3/8." It's very close to right and I could probably install it and go with it as-is but my OCD won't let me... pics later.

[Gjeep]

Seems like you're on the right track... Just know you're going to want to keep it to the renix years (87-90) as this is where you started from a pulling parts perspective. 91 was a different set up; '94.5 year-'96 got r134.