Air conditioning won't engage

Just picked up my very own jeep w00t! its a 98 and i've been busy fixing various problems (anyone in northeast ohio have a nss for sale?) including the AC. I'm quite handy in all sorts of this stuff including using a meter and this is where i'm at currently:

A put a gauge on the pressure port closest to the canister (i know its not an drier but i cant remember the name of the canister in the orifice system) and got 45 PSI which to me means I'm well within spec for pressure.

With the engine running, turn on the AC and the engine idles up slightly as if to prepare for the compressor. The clutch never engages. If i meter the line to the clutch it never gets voltage. The fuse in the engine bay is fine (large 20 amp fuse). If I pull the relay the connection that would normall engage the clutch has voltage but the relay never clicks over. If i meter the voltage to the relay coil it never gets voltage (not only that but i tried a known good relay). ALSO, i have jumped the low-side switch (closest to compressor) and i get the exact same response from the engine as if i just turned it on at the control panel so the switch checks out.

This seems obvious to me that its a switch or broken connection (another fuse somewhere that flips on the relay?) somewhere but I have no FSM or previous experience with the electrical system of this vehicle.

Suggestions on what to check next? thanks!

there could be lo refridgerant if the level is too low it wont let the clutch engage you could have a little refigerant enough to get the pressure up to 45psi but not enough volume to make the ac work properly there should be a pressure switch someware check if its getting power to it and if power is comming from it

i tried jumping the low side already and i still never get voltage to the relay coil. does the high side switch have any say as far as interrupting the clutch circuit?

IIRC, yes, it too must be closed for power to reach the clutch coil. It should, however be naturally closed and open only when too much pressure is present. It's been years since I played with automotive AC (windows work 'round here) but I would look at a quick jump of the HS switch and hit it with gauges before I went too far into it.

best of luck!
--Shorty

thanks, for whatever reason it didnt occur to me to jump this one too (other than the pressure looked spot on so i must have instictively ignored it). i'll have some more checking when i get home, next topic coming from me is overdrive/ torque converter lockup! oh boy! although i may hold off on that as i've almost an overload of things to try (50+ searched pages of reading i've done here at work)

thanks guys

good luck on all.... now get back to work!!!!!:rof:
--Shorty

for those that care i solved the problem. now my ac works, my reverse lights work, my CEL is gone and my transmission shifts. according to the manual FUSE slot 10 is supposed to be empty... well, a 10 amp fuse in slot 10 cured a whole hell of a lot of problems for it supposing to be empty. what gives? does anyone know why my manual says no #10?

Did that fuse correct your A/C problem. I am trouble shooting a similar problem. My a/c clutch isnt engaging. The blower motor comes on so I dont think it's a a/c-heater controls issue. I checked the fuse in the power distribution center and the relay for the clutch and they both seem fine.

I dont know much about a/c so I didnt know about the low and high pressure swithces. Where are these located? I am going to try to jump the low side. I had my a/c charged last year when I installed a new compressor so I would have thought my pressure would have been fine but maybe not? Glad to hear your a/c is working! Sorry Im so late

Dang did this thread die???

I have a similar issue on my 1990 XJ.

Refrigerant pressures are good.

Compressor clutch engages intermittently...with AC in MAX, fan blower on high (blower works)...the electric fan runs...however the clutch doesn't engage even when it should...

If I jump that wire to the pos term of the battery, the clutch engages immediately and cold air is produced

checked voltage at the wires running to the clutch and confirmed that they are low...about 10 volts...think it should be closer to 14

Relay is OK (swapped)

Old wire = voltage drop???


May run new wire from relay to clutch...IDEAS????

Thanks!

check the voltage at the input side of the relay to verify full voltage there first and then verify full voltage at the out put side. This would narrow the voltage drop to the wire from the relay to the clutch coil. I'd find any/ all the unions and splices between the relay and the clutch and clean them spotless before running another wire (I just prefer to avoid adding more mess than necessary)

Thank-you for the reply.
Connectors are cleaned and reconnected, voltage on green wire not much over 10v...not the relay or relay connectors (cleaned them too)...

she is 19 years old.

If i cut the green wire, which passes positive voltage from fuse panel thru ac switch and the low pressure switch and cap it...then splice that green wire from the relay with an inline fuse to positive power post 12V(box next to relays behind battery, has all the fusable links attached)...

Then fresh orange wire from the relay to the clutch with short run of 14 gauge...Splice the orange wire back in for fan diode...so fan runs when AC clutch trips...

When the relay trips (tied to fuel pump (ORN/BLK) and air cond clutch control(BLU W/TR) in ECU) , the clutch would get adequate voltage to engage each time, everytime...

Comments? About to undertake...

have you jumped out the low pressure switch to see if that makes the comp come on? intermittant operation is indicative of low refridgerant. and depending on outdoor temps that can be normal if its like only70 outside that isnt alot of load for the system and cycleing can be normal you should be seeing about 30 degrees differance(roughly) between outdoor air temp and exiting air temp from your vents. its best to check air temps while driving at highway speeds. also remember the air temp will be slightly warmer at high blower speed because it moves across the evap coil at a higher rate and has less time to dissipate its heat. it may be time for a shot of refrigerant. there are drop in replacements for r12 if yours hasnt been converted to 134.

See earlier post.
Yes, R134, charge is rock solid.
Voltage was ~10.4v at clutch connector when it failed to engage in conditions when it should have engaged.
again R134 system, system charged to specification.
executed plan above. works like charm.

BTW low pressure switch jumped in earlier troubleshoot sequence had zero effect

could removing one of the shims that sits between the clutch itself and the compressor solve this? When i had issues of intermittent ac, the air gap was within spec, it had my aircon guy stumped. But he removed a tiny shim and that was enough difference to ensure the clutch got engaged as and when i need it. If your voltage is low then maybe you have issues i dont know about, but maybe reducing this air gap with reduced voltage will help draw your clutch in to engage?

waspie said:

for those that care i solved the problem. now my ac works, my reverse lights work, my CEL is gone and my transmission shifts. according to the manual FUSE slot 10 is supposed to be empty... well, a 10 amp fuse in slot 10 cured a whole hell of a lot of problems for it supposing to be empty. what gives? does anyone know why my manual says no #10?

Click to expand...

Dang! I was having charging problems after a trip to Moab. Turned out to be some wires rubbed through and grounding out.

During my search for the short, I pulled all the fuses and checked them. The book says #10 slot empty, but alas, I had a 10amp fuse there.

I pulled it.

The next week I had no AC, then noticed I had no Back up lights, then the dome lights wouldn't come on with the front doors (back doors they work fine) and the electronic mirrors quit working!

I found these things out over a week or so, not sure when they started.

But, I'm going out right now and sticking that fuse back in the #10 slot, and see whats up!

I love the 'Search' function here! HB

AHA! I replaced the #10 fuse, and BAM! the A/C and back up lights are working again!

I also checked the other supposed 'open' fuse spots on my '99 Limited, and found that #18 runs the power adjust for the rearview mirrors, so thats fixed!

Now to figure out the dome lights......:cheers:

I had the same issue with my AC and reverse lights not working. Replaced the #10 fuse and now AC works. Not sure on the reverse lights though, I was too happy about having AC on the trails.