1998 Grand Caravan a/c always running

[vgb14]

The air conditioning compressor in my 98 GC is always running, even when I have the a/c switch and fan switch off. The only way for me to workaround this is to remove the a/c relay. Does anyone have any idea how to correct this condition? The car has a 3.3 l with front and rear a/c. Thank you.

[Mrbizness1]

Originally Posted by vgb14

The air conditioning compressor in my 98 GC is always running, even when I have the a/c switch and fan switch off. The only way for me to workaround this is to remove the a/c relay. Does anyone have any idea how to correct this condition? The car has a 3.3 l with front and rear a/c. Thank you.

perhaps the problem is the relay. I have replaced 2 on my 98

[vgb14]

Thanks mrbizness - that sounds reasonable. Could anyone tell me how I could test the relay?

[hundahunta]

swap it with another relay, possibly a fan or wiper, high beam

[vgb14]

I tried it swapping it with other identical relays, and I continue to have the same issue - it was a good idea, though. Does anyone have any other suggestions? Thanks for your help.

[RIP]

This is how I understand the "power on" function of the A/C system works based on scant info I can glean from a Haynes manual. You push the A/C botton on. That signal is received at the Powertrain Control Module (PCM). If the PCM is getting the correct voltage from the A/C Pressure Transducer indicating the high and low system refrigerant pressures are good, then the PCM applies a ground to the coil side of the A/C Compressor Clutch Relay. The contacts of this relay close and the power path to the A/C Compressor Clutch is completed, turning on the A/C system.

Based on that and the fact you have already proven the relays are good here's some possibilities:

> The A/C on switch is on all the time even when not depressed. To prove it I would disconnect the connector from the back of the HVAC Control Panel (CP) and find the contact on the CP that corresponds with the dark green wire. Using a ohmeter, you should see continuity come and go as you engage and disengage the switch. If the resistance never changes you'll need a new CP.

> You could be getting an errant ground between the PCM and the A/C Clutch Relay. With power off, remove the clutch relay and the PCM connector and check for continuity to ground at the contact that corresponds to the dark blue wire with an orange stripe at the relay socket. If you see it you'll have to check the harness and find the short to ground. Shake the harness and see if it comes and goes.

> The ugliest one. The PCM is bad, supplying a constant ground and unforunately it's very likely. You can inspect the connection at the PCM for bent/corroded/pushed contacts before spending bucks to change it. Rebuilt PCMs cost anywhere from $100 at a junk yard to $400 from a dealership. They run around $2-300 on the internet.

> EDIT - one more could be the clutch is stuck on. Watch the clutch spin when the A/C is on. Now turn the van off. You should see the clutch pop out and disengage. Bit of a log shot but, should be checked.

If someone has a factory schematic it may clarify it more. Hopefully you'll find an easier answer than all this but, if you want to tackle this I would recommend downloading the factory manual at Alldata.com or Mitchells for $15. The schematics and naratives should give you much more info. Haynes and Chiltons manuals are lacking in many ways.

[vgb14]

Thanks for your suggestions. I will post the fix once I get the problem resolved.