Freon good, system works when forced, but air conditioner will not work

Tiny
N2AUDIO
  • MEMBER
  • 2004 CHRYSLER TOWN AND COUNTRY
  • 3.8L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 188,000 MILES
Hello, I am a reasonably competent amateur mechanic although not well versed in A/C.

Earlier this spring my A/C worked fine. Then one day a couple weeks ago there was nothing. I located the clutch relay, pulled it, and shorted the power leads. The system worked and cooled. I have tested the relay for continuity when energized, also good. I have swapped that relay with an identical relay from a different circuit, no change. I have checked the clutch/compressor fuse is good.
I have tried a new pressure (trinary?) Switch, no help.

At that point I had a professional basic a/c service (evacuate, check for leaks, refill with precise amt of Freon/dye). The system checked out (slightly high on Freon, not enough to cause a problem), but they also were unable to get the compressor to run. I am currently unable to part with the vehicle for a full diagnosis.

After that I removed and disassembled my ICM (integrated control module, fuse/relay box under the hood) to check for signs of deteriorated wiring or burn marks, all looked good.
I removed my wheel well liner to inspect the PCM. There was some light surface rust on the outside and water stains, but no signs of obvious problems. I removed the four connectors and wiped everything down. The contacts looked clean.

I do not know what else to do.
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Thursday, June 15th, 2017 AT 9:07 AM

20 Replies

Tiny
KEN
  • ADMIN
Hello,

It looks like there is a compressor relay as well as several fuses that run the system. Here is a wiring diagram (below) and a guide to help you do some testing to get the problem fixed.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

and

https://www.2carpros.com/articles/how-to-check-wiring

See where the system is dropping the power or not getting signal

Please run some tests and get back to us so we can continue helping you.

Cheers, Ken

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Saturday, June 17th, 2017 AT 5:23 PM
Tiny
N2AUDIO
  • MEMBER
Thanks Ken. I had found some other schematics as well. These seem to be a little more detailed. I posted at the chrysler minivan forum and auto ac forum and got little help.
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Sunday, June 18th, 2017 AT 8:46 PM
Tiny
KEN
  • ADMIN
Please let us know what happens, we are interested to see what it is.

Cheers, Ken
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Monday, June 19th, 2017 AT 10:05 AM
Tiny
N2AUDIO
  • MEMBER
I have 12v+ at pin 30 of the a/c relay and 15 ohms from pin 87 to batt (-).
And I have 12v+ on pin 86 when the a/c switch is turned on at the hvac control.

I'm good to the relay, right?
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Friday, June 23rd, 2017 AT 7:19 AM
Tiny
KEN
  • ADMIN
Yep the relay is good it sounds like. Do you have power at the compressor?
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Friday, June 23rd, 2017 AT 11:08 AM
Tiny
N2AUDIO
  • MEMBER
I didn't go directly to the compressor this time, but if I pull the relay and short the 30/87 contacts the compressor runs and cools.
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Friday, June 23rd, 2017 AT 8:25 PM
Tiny
HMAC300
  • EXPERT
Off you short it and it works. Then it's fuse box not making contact try tweeking prongs onrelay and using dielectric grease on them to make compressor work
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Saturday, June 24th, 2017 AT 7:58 AM
Tiny
KEN
  • ADMIN
There is a air conditioner pressure sensor near near the throttle body that sounds like it is bad.

Use the wiring diagram above to test to see if its getting power.

Please let me know
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Saturday, June 24th, 2017 AT 10:41 AM
Tiny
N2AUDIO
  • MEMBER
I swapped in a new pressure sensor early on as a wild guess fix. Nothing changed.
I measured voltage on the 5v supply line at 4.9. The pressure sensor wire was 1.04 or 1.05v. I also measured continuity on the ground lead and got around 15 ohms which seemed a bit high, but I was using a very thin pin stuck through the wire as a contact so maybe not exactly accurate -- or something to do with using a random bolt up near the radiator as my other point of contact.
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Saturday, June 24th, 2017 AT 8:11 PM
Tiny
KEN
  • ADMIN
Does terminal 86 and 30 have power still?
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Monday, June 26th, 2017 AT 9:32 AM
Tiny
N2AUDIO
  • MEMBER
30's always hot. 86 gets 12v when the a/c button on the control panel is on.
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Monday, June 26th, 2017 AT 12:05 PM
Tiny
N2AUDIO
  • MEMBER
Hmac3000 I disassembled the whole fuse box to check for worn wiring or connections. If it was something like an opened up connection at a fuse I would think that would show up with just a wiggle test.
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Monday, June 26th, 2017 AT 12:09 PM
Tiny
N2AUDIO
  • MEMBER
Tech says evap temp sensor. Repair cost over 1k. I will either figure out how to do it myself or get by w/o a/c. I have no info on the sensor other than the tech saying the dash has to come out. Can't find a listing for the part either.
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Tuesday, July 11th, 2017 AT 9:42 AM
Tiny
HMAC300
  • EXPERT
I am assuming this is manual control if it were me i'd try going through glove box with it out and getting evap sensor as it is on top of hvac. There are only 2 bolts for that and harness but here is stuff in pics enjoy
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Tuesday, July 11th, 2017 AT 12:10 PM
Tiny
N2AUDIO
  • MEMBER
It's auto
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Tuesday, July 11th, 2017 AT 12:22 PM
Tiny
HMAC300
  • EXPERT
I think it will be the same but let us know about that stuff in future you are very lucky it's underhood and dash doesn't need to be pulled see pics.
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Tuesday, July 11th, 2017 AT 12:36 PM
Tiny
N2AUDIO
  • MEMBER
This can be done w/o evacuating the refrigerant?
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Wednesday, July 12th, 2017 AT 2:04 PM
Tiny
HMAC300
  • EXPERT
No evacuate then recharge as it looks like it's attached to expansion valve and that has to come off
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Wednesday, July 12th, 2017 AT 3:19 PM
Tiny
N2AUDIO
  • MEMBER
Got it done. Wasn't terribly difficult. Had some problem locating the part because the evaporator temp sensor on this vehicle is actually PART of the expansion valve. The dealership sold me the wrong part.
The OEM expansion valve is a $120 part. I found an aftermarket option for $32.
Also had a problem with the bolts holding the expansion valve to the firewall. The bolts thread into a block of aluminum and the threads partially stripped on removal. I had to buy a tap and die kit to clean the aluminum off the bolt. Luckily the female threads were intact enough to allow the bolt to tighten on reassembly.
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Thursday, August 3rd, 2017 AT 9:57 AM
Tiny
KEN
  • ADMIN
Nice work, we are here to help, please use 2CarPros anytime.

Cheers, Ken
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Thursday, August 3rd, 2017 AT 10:44 AM

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