A/C compressor will not come on unless relay is jumped

Tiny
JASON123177
  • MEMBER
  • 2008 CHEVROLET UPLANDER
  • 3.9L
  • V6
  • 2WD
  • AUTOMATIC
  • 247,000 MILES
I changed the front and rear expansion valves. When I went to recharge the system, after pulling and making sure the system held a vacuum of 30in/hg of course, it would not take a full can of refrigerant. I discovered that the compressor clutch wasn’t engaging. I know I’m not supposed to do this, but I jumped pins 30 and 87 on the clutch relay, and the compressor ran and sucked in refrigerant like there was no tomorrow. After putting the recommended 2.2lbs of R134a, I was getting readings of 205 psi on the high side and 48-50 on the low side but, the clutch still would not engage unless the relay was jumped. This led me to believe that either the control module or pressure transducer was bad. I got a control module out of a wrecked vehicle instead of forking out over $400.00 on a new one. Installed it, reset the PCM and tried the A/C again. Nothing changed at all. I installed a new pressure transducer yesterday, reset the PCM, and again, nothing changed. I did notice that there is a connector in between the condenser coil and grill that isn’t connected to anything. Could this be for an ambient temperature sensor, and could that be the cause of the compressor clutch not engaging? If not, what in the world is going on, because I am baffled at this point.
Do you
have the same problem?
Yes
No
Friday, July 19th, 2019 AT 5:09 AM

52 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good morning,

First, no need to reset PCM. If your repair was correct, it will come on by itself.

Did you verify power to the control side of the relay? I will attach a wiring diagram for you to view.

Also, the low side is way too high. It should be 25-30 lbs. Did you change the accumulator as well?

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 6:40 AM
Tiny
JASON123177
  • MEMBER
Good morning to you as well. Thank you for your prompt reply. I did not check to see if there was power to the relay. Never dawned on me. I did switch it out with two other relays that were exactly the same (horn and fuel pump) just to make sure the relay was good. Also, I did not change the accumulator either. What would cause the low side to be too high? The ambient temperature was about 94 degrees F when I last got pressure readings.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 6:51 AM
Tiny
ASEMASTER6371
  • EXPERT
The accumulator is required once the system is opened.

Check the power at the relay and let me know what you find.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 6:52 AM
Tiny
JASON123177
  • MEMBER
I will check it when I get home this afternoon and let you know. The accumulator is mounted on the drivers side of the condenser coil correct?
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 6:54 AM
Tiny
ASEMASTER6371
  • EXPERT
Nope, looks like it is on the condenser for your truck.

Picture attached.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 1:20 PM
Tiny
JASON123177
  • MEMBER
Yes, that is where I was talking about.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 2:43 PM
Tiny
ASEMASTER6371
  • EXPERT
Yep, be careful removing it. It is common for the bolts to seize when releasing the dryer.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 2:46 PM
Tiny
JASON123177
  • MEMBER
I have 13vdc at pin 86 and nothing at pin 85.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 2:57 PM
Tiny
ASEMASTER6371
  • EXPERT
What about 30? Do you have the power there?

85 is the ground to the PCM. It will ground the control side when it sees the correct signals from the pressure switches.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:02 PM
Tiny
JASON123177
  • MEMBER
Pin 30 is 0 pin 87 is 13vdc.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:04 PM
Tiny
ASEMASTER6371
  • EXPERT
That's your problem. You should have power at 30 all the time.

Check the wiring diagram I posted in the beginning. Check the AC clutch fuse for power on both sides with a test light or voltmeter.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:11 PM
Tiny
JASON123177
  • MEMBER
There isn t power on either side of the clutch fuse.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:14 PM
Tiny
JASON123177
  • MEMBER
I am going to post a video of me checking the pins. Something weird is going on.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:22 PM
Tiny
ASEMASTER6371
  • EXPERT
Okay, if there is no power to the fuse, the fuse box is the failure. It is common for failed fuses boxes with GM.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:28 PM
Tiny
JASON123177
  • MEMBER
When I connect to the battery ground, it does show power on both sides of the fuse. But, when I ground to the ground on the side of the fuse box it shows no power to either side of the fuse. The video is of me testing the relay plug off of the battery ground and the ground on the side of the fuse box.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:37 PM
Tiny
ASEMASTER6371
  • EXPERT
You need to put the black wire to the battery ground. Then test for voltage to the fuse with the fuse installed. You need power on both sides.

If you have power, then you have a wiring issue from the fuse to the relay terminal 30.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:41 PM
Tiny
JASON123177
  • MEMBER
Were you able to watch the video of me testing the relay plug?
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:42 PM
Tiny
ASEMASTER6371
  • EXPERT
Yes but it looked like the fuse was out.

Roy
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:44 PM
Tiny
JASON123177
  • MEMBER
The clutch fuse was in. The relay was out.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:45 PM
Tiny
JASON123177
  • MEMBER
Will it be possible for me to email you my phone number and have you to call me? It may be easier to go through this on the phone.
Was this
answer
helpful?
Yes
No
Friday, July 19th, 2019 AT 3:47 PM

Please login or register to post a reply.

Sponsored links