SPONSORED LINKS

Air conditioning not working?

Tiny
DAVID WILHITE
  • MEMBER
  • 1999 GMC SIERRA
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 195,000 MILES
Compressor quit, replaced compressor, dryer, clutch cycling switch (low pressure) and manifold hoses on compressor. Pulled vacuum, no leaks, jumped compressor at relay and added Freon. Now compressor will not come on even by jumping. Replaced PCM, still no power. What should I try next? David.
SPONSORED LINKS
Friday, June 5th, 2020 AT 2:57 PM

41 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

Do you have a test light to some testing at the relay?

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

We need to see if you have the signals for turning on the compressor.

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

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

Roy
Images (Click to make bigger)
Thumb
Thumb
Thumb
Thumb
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
+1
Friday, June 5th, 2020 AT 3:15 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
Yes, I have a test light and multi meter. I have tested the relay terminals and what I don't understand I have power to 87, but not 30.I thought it was the other way around. I tested the coil at the compressor and it works, but I can get no power to coil. If I jump 87 to 30 I still have no power to coil.
Was this
answer
helpful?
Yes
No
Friday, June 5th, 2020 AT 4:17 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, let us start by checking for 2 powers at the relay with the key on.

87 id the wire to the compressor.

30 and 85 should have power.

Roy
Was this
answer
helpful?
Yes
No
Friday, June 5th, 2020 AT 4:53 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
Key on, A/C on power to 85 and 87 none to 30.I did not replace the high pressure switch at rear of compressor.
Was this
answer
helpful?
Yes
No
Friday, June 5th, 2020 AT 5:19 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Again, you do not have power to 87. That goes directly to the compressor. 30 is the pin that has power, not 87.

Okay, go to the switches on the lines. Check for power to the switches. Let us see if they are getting power.

Roy
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Friday, June 5th, 2020 AT 5:28 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
I think the 30 is the lower left pin if I am standing by the left fender and 87 is the upper right pin. Do I have this backwards? Regardless, when these two are jumped, it does not engage the clutch. Thanks, Dave.
Was this
answer
helpful?
Yes
No
Friday, June 5th, 2020 AT 6:02 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
30 and 87 jumped should send power to the compressor.

With it jumped, check for power to the connector.

Roy
Was this
answer
helpful?
Yes
No
Friday, June 5th, 2020 AT 6:14 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
Okay, I was wrong on 30/87. I do have power to 30 and if I jump to 87 the clutch engages. With key on I have power to 30 and 85 but with relay in comp still will not come on. (Switched relays and no difference.) Is there another source that triggers the relay? Thanks.
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 9:48 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, a couple of posts ago, I told you to check the switches. You need to test for power to the switches. They send a signal to the ECM and when the ECM sees the correct signals, it will ground the load side of the relay and turn on the compressor.

Roy
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 9:56 AM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
Low pressure mounted on dryer, 8.3v switch on line going into condenser 10.0. Unable to get to high pressure switch on rear of compressor without removing compressor due to its location.
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 10:58 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Those are way too low. You need to have 12 volts to the switches.

Did you check both sides of the switch on the dryer? Hook up the switch and measure both sides. You will have to pierce the wires.

You need to get to the high pressure switch wiring. You need to check for voltage at and through that switch as well.

Roy
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 11:08 AM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
How do I increase the voltage? Also what is the difference in the different colored high pressure switches that are in the back of the compressor? Mine is light blue with an oblong female connector and all I can find have round female connector. Will a different color work? Thanks.
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 4:25 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
No, they need to be the same if it has to be replaced.

What are the voltages?

The control head controls those voltages.

Can you recheck those voltages?

Roy
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 4:36 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
First thanks for the quick reply's. Is the control head the same as the A/C module located in the dash, if so I have one on the way that is a refurbished and guaranteed for life. So far I have been unable to find a light blue high pressure switch that is like mine.
Was this
answer
helpful?
Yes
No
Saturday, June 6th, 2020 AT 4:57 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, why are you replacing the high-pressure switch? It does not make sense unless you have checked the voltage on both sides?

You need the proper voltage for it to work.

Roy
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Sunday, June 7th, 2020 AT 4:38 AM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
Just received new (rebuilt) ac controller. Disconnected battery installed controller, a 5 minute job and the battery was completely dead. Hooked up charger and there is a very loud buzzing coming from the device on the lower left of dash. Battery is near new and will not take charge when hooked up to car. What is this alum looking thing that is just by the park brake It seems there must be a very strong short.
Was this
answer
helpful?
Yes
No
Monday, June 8th, 2020 AT 11:55 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
I would either remove the battery and have it charged or get a new one under warranty.

Roy
Was this
answer
helpful?
Yes
No
Monday, June 8th, 2020 AT 12:18 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
The battery is near new and was filly charged before I installed the ac controller. I removed the controller and with charger hooked up the buzzing starts. What is this alum looking thing?
Was this
answer
helpful?
Yes
No
Monday, June 8th, 2020 AT 1:09 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Can you attach a picture?

Most likely from low voltage. You need to charge it to the full voltage of 12.6 volts.

Roy
Was this
answer
helpful?
Yes
No
Monday, June 8th, 2020 AT 1:20 PM
Tiny
DAVID WILHITE
  • MEMBER
  • 13 POSTS
It was low voltage, but I don't understand how a good battery could go completely dead in 10 minutes. I have now replaced compressor. Dryer, manifold lines from compressor, low pressure switch at dryer, ECM and A/C control module in dash and still the compressor will not come on. It will with a jump at the relay. It is fully charged 30/195. What next? Thanks, Dave.
Was this
answer
helpful?
Yes
No
Monday, June 8th, 2020 AT 5:17 PM

Please login or register to post a reply.

Related Air Conditioner Not Working Content

Fix an Air Conditioning Not Working Video
VIDEO
Fix an Air Conditioning Not Working Video
Instructional repair video
Air Conditioner Not Working
GUIDE
Air Conditioner Not Working
Like any sub system in today's car a problem and be minor or a little more involved, this guide will help you find the problem and perform repairs. You can be the judge if...
VIEW MORE

Sponsored links