Kedosp Posted July 15 Share Posted July 15 Hello everyone, I have an 88 MJ with original renix 4.0 that never had AC. I’ve added all the ac parts under the hood, swapped in an AC hvac box and replaced the dash wiring and controller. I can’t find a diagram for how to build a harness to hook to the 4 pin dealer AC connector. I know it includes a relay, 2 wires for the pressure switch and one for the compressor clutch. Can anyone provide a diagram, or close up pics of the wiring? I found this pic but can’t see the details I need. Link to comment Share on other sites More sharing options...
fiatslug87 Posted July 15 Share Posted July 15 Try these https://comancheclub.com/topic/12083-electrical-manual/#comment-117394 https://comancheclub.com/topic/11875-renix-factory-service-manual/#comment-115082 Link to comment Share on other sites More sharing options...
Kedosp Posted July 15 Author Share Posted July 15 Thanks fiatslug87! I should have mentioned I downloaded the electrical FSM and reviewed it but it doesn’t seem to include the dealer AC diagram, only the below diagram for the wires on the jeep side of the 4 pin connector. Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 15 Share Posted July 15 Oh look! My picture from my 2.5L AC post. Ok so that harness has an in-line circuit breaker and a relay that can be seen. I will go look at my electrical books and see what I can find for ya. Link to comment Share on other sites More sharing options...
Kedosp Posted July 15 Author Share Posted July 15 Eaglescout526 - yes, you had the only picture I could find anywhere of that harness! Appears to be the same for the 2.5 and the 4.0 Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 15 Share Posted July 15 I’m not entirely surprised. I got really lucky to find that as NOS. Without really tearing my harness out to figure it all out at the moment, I haven’t been lucky to find anything in relation to that harness anywhere. I’m gonna check my 86 manual and see if anything is there. But no luck in my 88 or 89 manual. Link to comment Share on other sites More sharing options...
Kedosp Posted July 15 Author Share Posted July 15 Assuming you still have that jeep, If you can take pics of the wires for the connectors and relay that would probably work Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 15 Share Posted July 15 Of course!! That MJ is my baby! I’ll snap all the pics of the colors of the wires here in a bit. Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 15 Share Posted July 15 Link to comment Share on other sites More sharing options...
Kedosp Posted July 15 Author Share Posted July 15 Thanks a ton for getting those pictures so quickly! I noticed there is a grey wire on one of the relay terminals. Can you tell where that ties into the 4 wires from the connector? You mentioned there is a circuit breaker on the harness. Is that the small component with white wires feeding it labeled 7Y02? That’s an odd looking circuit breaker, are you confident that’s what it is? Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 15 Share Posted July 15 I believe the grey goes to the compressor. Yes that is the circuit breaker. It’s there in the event the in-line diode to the compressor we’re to fail. Link to comment Share on other sites More sharing options...
Kedosp Posted July 20 Author Share Posted July 20 I think I have most of it figured out, can you confirm if I’m on the right track with where the wires run to? I used your relay picture and the other one below to hopefully figure out where the wires go for the relay. The numbers are upside down, but I think that’s the same orientation as your relay in the picture. Where in the harness is the inline diode? 4 pin connector wires Green - pressure switch, then to relay 30 White - breaker then to relay 30 Orange - to relay 85 Black/blue - to relay 86 Relay wiring 30 green & white (2 wires) 85 orange 86 black/blue 87 grey (output to compressor) Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 20 Share Posted July 20 Yeah looks like you got it right. Diode should be close to the compressor. That one is a little tough to explain but it should be in the electrical manual. Link to comment Share on other sites More sharing options...
pizzaman09 Posted July 21 Share Posted July 21 It would be challenging for me to get the photos as my truck has a ton of junk under the dash with cruise control, but my truck has dealer installed AC, (by a dealer) let me know if there is something you need. Link to comment Share on other sites More sharing options...
Kedosp Posted July 21 Author Share Posted July 21 Thanks pizzaman09! I hopefully have the under dash wiring sorted out already. It’s the engine bay harness that I’m missing and with Eagle’s pictures I should have that built soon. I’ll post updates once I do. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted July 22 Share Posted July 22 The diode is like a one way check valve for the AC clutch power. It should be located inline near the AC clutch. Its purpose is to prevent the clutch from back feeding electrical current when the clutch is cycled off. I've run without them before in an MJ ac system but they are good insurance and should be installed. The diode should have a symbol of some sort indicating the direction of current flow. Again, just think of this as a check valve Link to comment Share on other sites More sharing options...
Kedosp Posted July 22 Author Share Posted July 22 I’m familiar with how diodes work, and I believe my compressor has one in the short section of wiring that came attached to it. Seems to match this part of the wiring diagram. The part that is bothering me is the “breaker” labeled 7Y02 in Eagle’s harness. I almost think that’s a diode as well since the white wire it’s inline on and the green wire both feed the 12v trigger terminal of the relay to engage the AC clutch. Seems odd there would be 2 wires feeding that, and I don’t think 12v flowing back into the other trigger wire seems right. What are your thoughts? Obviously you know your stuff Eagle, and your AC has worked for years. Just trying to understand how this harness works and make sure I get it right. Link to comment Share on other sites More sharing options...
Ωhm Posted July 22 Share Posted July 22 The 4.0L uses a Fan Diode Assembly (C246) which allows the electric fan to kick ON when the AC clutch is engaged but will not allow the AC clutch to kick ON the electric fan. Link to comment Share on other sites More sharing options...
Kedosp Posted July 22 Author Share Posted July 22 Then that has to be a diode taped to eagles harness. Searching google for “Jeep Cherokee electric fan diode” comes up with a few results showing an orange version of that component. Pic below My truck doesn’t have the heavy duty cooling. I do have an OEM electric fan that I installed, but haven’t started on figuring out how to wire that yet. Was planning to use stand alone relay and a temp sensor in the newer style thermostat housing I added when upgrading my cooling system. I might just leave the white wire disconnected from the AC relay if it feeds the stock fan relay that doesn’t exist in my harness. Link to comment Share on other sites More sharing options...
Ωhm Posted July 22 Share Posted July 22 21 minutes ago, Kedosp said: Then that has to be a diode taped to eagles harness Not sure on the 2.5L if the electric fan is ON when the AC clutch is engaged. 23 minutes ago, Kedosp said: My truck doesn’t have the heavy duty cooling Since heavy duty cooling was an option needed for Dealer Installed AC, might not have all the necessary wires. Not sure here. Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 22 Share Posted July 22 2 hours ago, Ωhm said: Not sure on the 2.5L if the electric fan is ON when the AC clutch is engaged. 2.5L never got an electric fan during its run. Good ole fashion clutch fan. About that diode or breaker, I think it’s a breaker to prevent an overload or in the event the diode fails and grounds out the compressor. Link to comment Share on other sites More sharing options...
Htchevyii Posted Wednesday at 08:44 PM Share Posted Wednesday at 08:44 PM I need to try to get this figured out. My wife has been incredibly patient, especially for someone who hates the heat, but she kept saying how nice it was to have AC on our recent trip in the Ram. Planning desert trips 6 months in advance when you have a black truck with no AC has been problematic. I installed an AC heater control and evaporator box already, but now it's time to finish the job. Any updates on the underhood wiring progress would be appreciated. Link to comment Share on other sites More sharing options...
Kedosp Posted Thursday at 07:08 PM Author Share Posted Thursday at 07:08 PM I tried wiring it using the pictures from Eagles NOS dealer harness for the 2.5L and built a replica harness but it would not work. Power was not getting to the relay terminals how it should. Below is how I wired it which has been working great. Only thing I may eventually try to figure out is the ECU doesn’t know the AC is on so the RPM’s drop a bit with the AC on. If the engine is not warmed up it will occasionally die. I only used 2 wires of the dealer harness connection: Orange wire with black stripe in terminal B is the 12v power source for the relay. Green wire with black stripe in terminal A sends power when the AC controller is moved to an AC position. I used this as the trigger to turn the relay on but first ran the wire to the low pressure switch and back to the relay. (This will prevent relay from turning on the compressor with low pressure) Then I ran a single wire from the relay output terminal to the compressor. Don’t forget to ground your relay or it will not function My new compressor already had a diode inline with the short single wire that came attached to it so I didn’t add one in my wiring. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted Thursday at 11:09 PM Share Posted Thursday at 11:09 PM Ultimately, you need to get 12v+ to the compressor and power to the blower motor and you’ll have AC. You’ll also need an AC pressure switch which can cycle the compressor on and off as needed. Those are the bare minimums assuming you have your refrigerant lines plumbed already. If I were adding AC to an MJ, I’d use the factory under dash ac harness. It is a fairly stand-alone harness. It will provide you with variable fan speed via the resistor, integrate the evaporator freeze sensor (not a must have but nice to have) and have all the necessary connections for the hvac deck. Link to comment Share on other sites More sharing options...
eaglescout526 Posted yesterday at 01:02 AM Share Posted yesterday at 01:02 AM Well the harness is supposed to help the ECU know when AC is requested as the REM sees it. Which I think is the point in the diode or resistor or breaker or whatever the hell it is at this point. A work around this is to have a idle adjust harness that was part of a campaign that addressed a customer complaint about too much vibration from the 2.5L when the AC is off or on non equipped AC Jeeps. But even that has some sort or resistor or something in it that helps step up the idle. That’s how I got my XJ to work with the AC system that’s installed. There was no way I was gonna be able to make a whole new harness to have the ECU see the AC when I had one of those harnesses. Link to comment Share on other sites More sharing options...
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