ac electrical problem, no power to compressor

[CLOISER]

my ac blows warm, coolant pressure is good but no power to the compressor, I think the clutch for the compressor may be bad as well because when I send power to it it won't engage but the fuses are good...so...

how should I attack this problem, I really don't like electrical bugs but I really need AC...please let me know where to start

 

[kastein]

Check the high and low pressure switches on the AC lines for continuity, at least on a 98 (what year is yours?) both have to activate before the compressor will turn on.

First problem to figure out is why the compressor won't turn on... try poking the clutch with a piece of wood while the engine is running and you have it energized, if it kicks in, your clutch needs some shims removed or needs to be rebuilt. Once you've got that fixed find out (if necessary) why the wiring isn't telling it to turn on - this is all the relays, ECU, switches, etc. First and foremost is the clutch though since you know it has a problem.

 

[CLOISER]

ok I connected a wire direct from battery to compressor and it engaged no problem, so I think I need to check the switches and relays, not sure how to go about that, also it is a 1998

 

[MrShaft696]

are you sure you have enough refrigerant in the system?

 

[CLOISER]

I'm going to advance to pickup the gauges now, I checked it but didn't have the compressor running, the pressure was 100 lbs on high side but I forget the low so I gotta pick up the gauges

 

[CLOISER]

it's good on refrigerant and I can get it to blow cold when i run wire from battery right to the compressor, how do I go about checking these switches to see which is at fault?

 

[CLOISER]

anyone? trying to get going on something so my friday night doesn't go to waste

 

[weebur]

It could be the AC relay. It's in the PCM box, passenger side fender under the hood...on my '97 anyway. Mine went bad.

 

[CLOISER]

thanks weebur, I was thinking maybe could be relay, I think I'll change that first, probably like 35$ then move on from there

 

[CLOISER]

replaced the relay still no good, have no idea where to start since chilton's leaves me high and dry on ac repair :soapbox:

 

[weebur]

If you're serious about doing this fix yourself start by picking up the Haynes tech manual for heating and AC. It will give you a good idea on how AC works. If you haven't already done this get a piece of solid mechanics or other stiff steel wire, cut about 4", clean the ends, form it into a U and insert the ends into the disconnected low pressure switch connector. Start the vehicle, AC on recirculate, fan on high. Your compressor should run full time. If not jiggle the relay in and out.

There was a TSB in '99 regarding faulty calibrated low pressure switches, the fix is a recalibrated switch, part number (for 1998 and 99) is: 05015872AA. I mention this for two reasons. One is if by jumping the connection the compressor runs then you may have a bad switch and if you need to replace it then get the recalibrated switch. It was redesigned to help prevent evaporator freeze up. The other is if you get your system running and to run into the fairly common problem of the air working for a while, then stopping, then after shutting it off it starts working again (ice melts off the evaporator) you can think about getting the new switch from a dealer.

You mentioned that the high side pressure was 100psi. That sounds too high for the compressor not running. With the AC off the low and high side pressures should be roughly equal (Haynes says about 70psi). If your system is over filled the high pressure cutoff switch (near the compressor) won't allow the compressor clutch to engage.

If you have access to professional style gauges (two gauges-three lines, blue/yellow/red) hook up the gauges run the engine/ac on/fan on and jump the compressor as you did before and see what the low and high pressures are. I think mine was about 35psi (low), 225psi (high) with the switch connection jumped and the compressor running. Get back to us with a progress report.

 

[CLOISER]

thanks weebur, I tried jumping all the switches, still the only way I could get compressor on was direct from battery

I've got a gauge set for home ac system, don't think it'll mount up, saw them at autozone for $40 or so, thanks for your help, I don't even mind lack of ac but my girl sure does :scared: so I gotta get it working

 

[weebur]

Good luck. I got my gauges from O'Reilly's, I think I paid about $86, they're Interdynamics (some guys don't like them but they work fine for me). Sounds like you've already checked the fuses too, if not start there and maybe pull the center facia and heater/ac control and try jumping/wiggling that switch while the low pressure switch is jumped. Got to take my grandson for a haircut but will check back later.

 

[CharlesS]

replaced the relay still no good, have no idea where to start since chilton's leaves me high and dry on ac repair :soapbox:

If you need some assistance I own a 1998 XJ and have the Jeeps Factory Service Manual; which may help troubleshoot your problem.
Let me know if I can be of assistance.

 

[CLOISER]

Yes, do you perhaps have the resistance for the various ac switches, gonna check them out tomorrow after I look through some wiring diagrams I found online

 

[Zel94XJ]

O.P. Did you resolve the issue?