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Unread 08-24-2010, 02:06 PM   #1
nlepisto
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AC wiring question

So i got an ac system out of a 94 yj, my jeep didnt have ac before. does my jeep have the wiring harness under the dash even though i didnt have ac? the fuse box under the hood has a missing slot for a relay. this link MJR Features: Jeep Tech Writeups, Installations & Articles » YJ Aftermarket Air Conditioning Installation shows how to wire it towards the bottom of the page, and dosent seem like they use a relay at all, they hooked it up to the cruise control and wired the evap directly to the drier. is this safe/smart? or should i use Santech/Relay - A/C Connector (MT0911) | Relay - A/C Connector | 1994 Jeep Wrangler 4WD 4 Cylinders P 2.5L MFI | AutoZone.com that thing and just plug in a relay?

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Unread 08-24-2010, 04:38 PM   #2
laybackman
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Quote:
Originally Posted by nlepisto View Post
So i got an ac system out of a 94 yj, my jeep didnt have ac before. does my jeep have the wiring harness under the dash even though i didnt have ac? the fuse box under the hood has a missing slot for a relay. this link MJR Features: Jeep Tech Writeups, Installations & Articles » YJ Aftermarket Air Conditioning Installation shows how to wire it towards the bottom of the page, and dosent seem like they use a relay at all, they hooked it up to the cruise control and wired the evap directly to the drier. is this safe/smart? or should i use Santech/Relay - A/C Connector (MT0911) | Relay - A/C Connector | 1994 Jeep Wrangler 4WD 4 Cylinders P 2.5L MFI | AutoZone.com that thing and just plug in a relay?
Here is a link to a pdf I put together for you. I will keep it up for a while. It shows the stock AC wiring in a 94YJ with the 4.0 engine. I don't think AC was offered with the 2.5. Note that this is stock wiring. You might need to add the AC relay in the PDC to energize that AC circuit.

http://home.comcast.net/~laybackman/94_YJ_AC.pdf
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Unread 08-24-2010, 06:00 PM   #3
nlepisto
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Quote:
Originally Posted by laybackman View Post
Here is a link to a pdf I put together for you. I will keep it up for a while. It shows the stock AC wiring in a 94YJ with the 4.0 engine. I don't think AC was offered with the 2.5. Note that this is stock wiring. You might need to add the AC relay in the PDC to energize that AC circuit.

http://home.comcast.net/~laybackman/94_YJ_AC.pdf
cool thanks for that, ive been trying to find one forever haha. so i bought the AC relay and the AC circuit u mentioned. now im just trying to find out how to wire it all up. kind of confusing having to do this not on the stock stuff. so according to that diagram i have to wire it to the heat on/off? or is this a completely seprate set up since i never was supposed to have ac? so what i see is there is 3 wires connecting to the harness on the evaporator side, LT BL, WHITE, and DK BL. and 1 black wire coming from the compressor. the relay circuit/relay have 5 wires coming from it. thats where im kinda lost, to what wires go where. i know which are the ground and to the battery and thats it : / ill study that diagram more, Thanks a bunch
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Unread 08-24-2010, 06:30 PM   #4
laybackman
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Originally Posted by nlepisto View Post
cool thanks for that, ive been trying to find one forever haha. so i bought the AC relay and the AC circuit u mentioned. now im just trying to find out how to wire it all up. kind of confusing having to do this not on the stock stuff. so according to that diagram i have to wire it to the heat on/off? or is this a completely seprate set up since i never was supposed to have ac? so what i see is there is 3 wires connecting to the harness on the evaporator side, LT BL, WHITE, and DK BL. and 1 black wire coming from the compressor. the relay circuit/relay have 5 wires coming from it. thats where im kinda lost, to what wires go where. i know which are the ground and to the battery and thats it : / ill study that diagram more, Thanks a bunch
Check below the radio and behind the heat control panel there may be a plug or plugs that you need. The stock dash harness may have all the plugs needed. The heater control panel you have now is probably not the one that comes with the factory AC already installed. That I wouldn't know. But I am glad to have helped you with the stock wiring information. I am not familiar with the system you are installing but maybe with information you now have you will get it up and running.
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Unread 08-25-2010, 12:56 AM   #5
nlepisto
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Originally Posted by laybackman View Post
Check below the radio and behind the heat control panel there may be a plug or plugs that you need. The stock dash harness may have all the plugs needed. The heater control panel you have now is probably not the one that comes with the factory AC already installed. That I wouldn't know. But I am glad to have helped you with the stock wiring information. I am not familiar with the system you are installing but maybe with information you now have you will get it up and running.
okay so i have finally figured it out, what wires to route where. but its telling me to route wires to the ecu, the diagram you posted shows 3 wires leading to it with the numbers 28,38, 27 are those the labeling of the wires? i REALLY dont wanna mess up my computer... the haynes i just picked up said there should be an ac harness there, so i guess i just need to know if those numbers are the actual labels for what i need to splice
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Unread 08-25-2010, 07:21 AM   #6
laybackman
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okay so i have finally figured it out, what wires to route where. but its telling me to route wires to the ecu, the diagram you posted shows 3 wires leading to it with the numbers 28,38, 27 are those the labeling of the wires? i REALLY dont wanna mess up my computer... the haynes i just picked up said there should be an ac harness there, so i guess i just need to know if those numbers are the actual labels for what i need to splice
Pin 27 on your PCM is circuit 19, a 18AWG LB wire, is for A/C REQUEST.
Pin 28 on your PCM is circuit 20, a 20AWG BR/RD wire, is for A/C SELECT.

Now I read on the pdf I posted for you that pin 34on the PCM is circuit 13, a 18AWG DB/OR wire, is for A/C COMPRESSOR CLUTCH RELAY.

Attached is a pdf of the 94 YJ PCM plug note the pinouts I mentioned. Does your set up have it's own relay? If so that is way they are telling you to go direct to the wires they point out. But you note that pin #38 is not for AC.

There is a plug under the dash near the steering column that may have these wires. EDIT: Look at page 2 of the first pdf I posted a link to that plug I mentioned is there.

http://home.comcast.net/~laybackman/94YJ40PCM.pdf
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Unread 08-25-2010, 03:36 PM   #7
sconnell
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I also am putting in factory AC in my 95 Sahara. I cant seem to find the harness either. If anyone knows where it is, can you please let me know. Also if anyone figures out how to wire it up any other way please let me know.
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Unread 08-25-2010, 04:00 PM   #8
nlepisto
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Quote:
Originally Posted by laybackman View Post
Pin 27 on your PCM is circuit 19, a 18AWG LB wire, is for A/C REQUEST.
Pin 28 on your PCM is circuit 20, a 20AWG BR/RD wire, is for A/C SELECT.

Now I read on the pdf I posted for you that pin 34on the PCM is circuit 13, a 18AWG DB/OR wire, is for A/C COMPRESSOR CLUTCH RELAY.

Attached is a pdf of the 94 YJ PCM plug note the pinouts I mentioned. Does your set up have it's own relay? If so that is way they are telling you to go direct to the wires they point out. But you note that pin #38 is not for AC.

There is a plug under the dash near the steering column that may have these wires. EDIT: Look at page 2 of the first pdf I posted a link to that plug I mentioned is there.

http://home.comcast.net/~laybackman/94YJ40PCM.pdf
okay so under the dash there is nothing that looks like the harness shown on that second page. i saw this sensor looking thing, on the picture out of my haynes shows that this MIGHT be the ac harness and maybe the sensor type thing is just a cap? 3 of the 5 wires match up to the wiring diagram. what do you think?
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Unread 08-25-2010, 04:03 PM   #9
nlepisto
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also since my last post i pulled up my fuse box under the hood and there is no wires coming out of where the AC relay should be. so does that conclude the quest for the harness under the dash?
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Unread 08-25-2010, 05:14 PM   #10
sconnell
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Hey I found my wire harness I was looking for. I plugged in my factory A/C harness and the fan come on and the cigar lighter worked. Now I need to just add the A/C relay to the PDC and figure out which wires go to the high pressure sensor. I have a harness with two wires in it near the dryer, but the harnes dont fit the pressure switch. If anyone has a picture of this harness please help.
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Unread 08-25-2010, 05:35 PM   #11
nlepisto
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Quote:
Originally Posted by sconnell View Post
Hey I found my wire harness I was looking for. I plugged in my factory A/C harness and the fan come on and the cigar lighter worked. Now I need to just add the A/C relay to the PDC and figure out which wires go to the high pressure sensor. I have a harness with two wires in it near the dryer, but the harnes dont fit the pressure switch. If anyone has a picture of this harness please help.
did you have ac before your install? i didnt and under my PDC there were no wires coming from where the AC realy is supposed to go, so i had to buy the wiring part from napa. but where did you plug ur factory ac harness to? just to double check, under the dash? what color wires lead into it? just to verify. thanks
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Unread 08-25-2010, 05:39 PM   #12
sconnell
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It is under the dash on the drivers side. Reach up by your gas pedal and grab the big fat black wire loom, it is like your main harness. The ac harness is taped to that big wire loom. It has five wires into the harness, Black, Purple White, Light Blue, Light BLue w/BLack tracer, I think. The harness color is black. I didnt have A/C before I put this in. I also have another tub that is a 92 and the harness is there in that one too. Just look some more, I didnt find the first few times I looked myself. Hope this helps.
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Unread 08-25-2010, 07:23 PM   #13
nlepisto
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Quote:
Originally Posted by sconnell View Post
It is under the dash on the drivers side. Reach up by your gas pedal and grab the big fat black wire loom, it is like your main harness. The ac harness is taped to that big wire loom. It has five wires into the harness, Black, Purple White, Light Blue, Light BLue w/BLack tracer, I think. The harness color is black. I didnt have A/C before I put this in. I also have another tub that is a 92 and the harness is there in that one too. Just look some more, I didnt find the first few times I looked myself. Hope this helps.
cool thanks for that info. i see it now, the reason i didnt notice it before is cuz the male harness coming out of my evaporator thing is white and has 3 prongs and only 3 wires coming out of it. i think the previous owner cut them and used a universal harness thing... thats why it was so confusing.. haha but thanks.
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Unread 08-26-2010, 11:25 AM   #14
nlepisto
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Quote:
Originally Posted by sconnell View Post
Hey I found my wire harness I was looking for. I plugged in my factory A/C harness and the fan come on and the cigar lighter worked. Now I need to just add the A/C relay to the PDC and figure out which wires go to the high pressure sensor. I have a harness with two wires in it near the dryer, but the harnes dont fit the pressure switch. If anyone has a picture of this harness please help.
hey let me know when you wire up your relay and how ya did it, im in the process of doing it now. i have everything wired up except the black wire to the relay, if you look at the wiring diagram, it redirects you to a different page i dont have haha, so where did u wire your black one up to? is it just a ground?

Last edited by nlepisto; 08-26-2010 at 12:35 PM..
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Unread 08-26-2010, 02:41 PM   #15
sconnell
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All my wiring is there for AC, all I have to do is put in the relay and find the harness for my dryer. I found a two wire harness near my dryer but it isnt gonna fit my high pressure sensor, the harness is different. What does your harness look lik or do you not have one? If I can get my PDC apart I can take a look a it and let you know where the wires go.
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