JonRedcorn

Hey guys, I just picked up my first XJ, it's a 97.

I am trying to diagnose why my AC clutch is not kicking on normally. The system had a leak by the condenser which I fixed, and then pulled a vacuum and proceeded to charge the system up and the clutch would never turn on. I tried jumping the low pressure switch, nada, high switch, nada, had to replace the big 20 AMP fuse in the engine bay fuse box as it was popped. The fuses by the kick panel seemed to be fine. I then wanted to see if the clutch worked at all and it does, I jumped it straight from the battery and it started turning. I am trying to figure out what I am missing here. I ran out of daylight today and tomorrow will check out the relay in more depth. Just curious if there is anything I should be checking besides the things I've already done. I would very much appreciate any help as summer is right around the corner here in Florida and no AC sucks.

Thanks.

4.3L XJ

Since you seem to have some knowledge, trace the electrical circuit backwards. First thing I would do is verify power to the low pressure safety switch. In nothing, i would look at the AC controls in the dash next.

JonRedcorn

Sounds like a plan. Tomorrow I will definitely bust out the voltage tester. Probably should have today but oh well. Thanks for the speedy reply my friend.

awg

download the FSM free and look at the electrical circuit diagram, that helps, if you are a new owner you may not know about it

JonRedcorn

Pretty sure I got a manual off this russian site. It's pretty extensive and has all the wiring diagrams.

I did a lot of testing today, basically everything seems to be functioning besides getting signal from the PCM to click that relay over. I took the PDC apart everything looks perfect. If you fiddle with the AC relay it will click over the compressor for a half second. I can't figure out if it's the PCM or what. I've tested for continuity at every connection and it all seems fine. I feel like I am missing something here. Maybe the coolant temp sensor? My AUX fan does not turn on when I turn the AC on. I don't know if it should or not.

I get 12 volts at both relay connections, the always on 12 volt post and the 12 volts when you turn the key, all fuses and relays are working. I am basically at a loss at this point. I can jump the relay and the compressor kicks on but that's just sending 12v straight to the compressor. I feel like I am missing a ground somewhere or my PCM is bad. Been pouring over the diagrams, and the trouble shooting steps. All the wiring seems to be in perfect shape.

Tomorrow when I get off work I will post some pictures to illustrate some issues I am seeing. Hopefully that can help with the diagnoses. If I can't figure it out I will take it somewhere since the system works I just can't get this wiring working. I really would hate to do that since I don't trust most AC shops here in Florida.

I want to mention that the 20 amp fuse for the AC compressor in the PDC was blown when I started this adventure. Could mean something I guess. Just don't know what I can check at this point. The system does work, when I jump the compressor it starts blowing cold air out of the vents.

bluejeep2001

Didnt have time to read entire post...aux fan only kicks on with ac on 99 and below. Anything later its temp driven only. If the clutch does not engage ...neither will the fan if 99 and below

djgrayxj

Note from DJ

You stated that you wiggled the A/C Clutch Relay and the clutch engaged monetarily.

Recheck the 20Amp Fuse to see if it is blown again.

If not pull the clutch relay completely out and look for any signs of corrosion on the pins or in its connectors.

Also give a good look at the outside of the relay for any cracks.

If all is ok try swapping the clutch relay with the one that is beside it; I think it is for the fog lights so it will not affect anything but the fog lights if the relay is defective.

Please keep us posted to of any progress or lack of!

4.3L XJ

If you wiggle the relay and it makes stuff work, either the relay is shot or you have a corroded connection. One way to check this is to straighten a paper clip and then bend it into a horseshoe position and insert it in the #30 and #89A socket. This will mimic the relay being on

JonRedcorn

I just want to make it clear, I have a brand new relay, which also didn't work and I've taken apart the PCD and the connections are perfect. Everything's tight which is just mind boggling to me, I can't understand what else it could be. It also isn't really a wiggle but when you first place the relay into the socket it clicks on for a second. This happens with both the brand new relay and the old one. I have jumped the posts and it does kick the compressor on. I've checked continuity between pretty much everything and it all seems fine. The switch wiring in the dash is fine. Everything looks brand new basically. No corrosion on anything. This is what's really got me stumped. The relay seemed like the culprit or at least the relay connections but like I said they look perfectly fine. I am going to get some alligator clips and put them into the connectors so I can test the voltage at the posts of the relay while it's plugged in. Haven't gotten a chance to work on it today as it's pretty cold and I've been working all day.

What I did notice was that the switch wiring from the dash to the PCM seems to not send very much voltage, I can't find what voltage should be being sent to the PCM. I am getting like .8 volts to C23 on the grey PCM plug. Might be C22 I can't remember. Either way it's not very much power. But again I do not know what is supposed to be being sent there. There is a change from nothing though.

Also my AUX fan does not turn on when I turn the AC on. It will only turn on if I unplug the coolant temp sensor. I am not sure if that's telling the PCM to shut the compressor off or not. Somebody here said pre 99 it should come on with the AC, and my jeeps a 97.

4.3L XJ

.8 volts is not enough. It should get 12 volts from the dash and to the relay

JonRedcorn

Sounds like I have a short somewhere between the dash switch and the PCM then? Or the switch is bad? Also a short would explain the popped AC clutch fuse in the PCD.

So C1 on the grey PCM port to the relay should be sending 12 volts when the AC is turned on?

C23 on the grey PCM port from the switch in the dash is getting the low voltage.

relay has hot 12volts on B5 all times, thats working, 12 volts on B1 with the key turned on thats working, but I am not getting signal from the PCM and you are saying it should be sending 12 volts to B3?





I am not sure if I am allowed to post this but this is what I am referencing. It also has the AC heater controls schematics I can post that as well.

Also want to say thank you guys for the help it is very much appreciated.

4.3L XJ

I would check the current in and out of that switch before I went any farther. Which is why I suggested checking that welector switch a few posts back

JonRedcorn

Yeah not sure why I missed that part.

Sounds like it's probably the culprit which would be really great if it's just a bad switch. Some parts of the switch seem to work but maybe thats the vacuum controlled portion? I do not know. The doors and vents seem to work fine when changing the ****.

4.3L XJ

I had the same problem on my Crown Victoria. I wired in a manual switch for the compressor since I couldn't find a new selector

JonRedcorn

I've certainly thought about it, but I am pretty sure the compressor needs to turn on and off under certain conditions?

That's funny cause I also daily a crown vic right now that has ICE COLD air conditioning. But the TQ converter is on it's way out, which is why I am trying to get this jeep ready to daily.

Also it seems from the reading that the switch actually enables a ground connection which is what signals the PCM, I actually don't exactly know how to test for ground so I need to figure that out. It seems it also grounds the relay which activates the relay switch, this ground gets sent out of the PCM by way of port C1. So basically c23 and c1 just complete a ground to the AC comp relay, which then kicks the switch in the relay sending power to the compressor. I must not be getting a good ground somewhere. Very possible.

I know this is for a jeep TJ but the schematic looks extremely similar and it operates almost exactly the same, seems this guy had the same exact problem I am having..

https://www.justanswer.com/jeep/7wmw...mper-wire.html