2012 Sierra 1500 AC issues

[Fishbones]

I just started having AC issues with my 2012 Sierra.

The symptom is blowing warm air on all vents. 

Here is what I have checked so far.

Compressor clutch appears to be engaging and cycling 

I checked all fuses and relay, no issues.

The only thing I have notices is the short line that comes from the firewall is very cold / frosted. This line is approximately 12 inches long.

The coldness stops when it hits the first line connector.

As far as AC compressor - At first start the clutch engages, runs continually, Short AC line frosts up. After idling for several minutes the AC line thaws out some but is still cool and the compressor clutch starts cycling on and off every 5 seconds. 

Any suggestions on what to look at next would be appreciated.

 

[newdude]

2 hours ago, Fishbones said:

I just started having AC issues with my 2012 Sierra.

The symptom is blowing warm air on all vents. 

Here is what I have checked so far.

Compressor clutch appears to be engaging and cycling 

I checked all fuses and relay, no issues.

The only thing I have notices is the short line that comes from the firewall is very cold / frosted. This line is approximately 12 inches long.

The coldness stops when it hits the first line connector.

As far as AC compressor - At first start the clutch engages, runs continually, Short AC line frosts up. After idling for several minutes the AC line thaws out some but is still cool and the compressor clutch starts cycling on and off every 5 seconds. 

Any suggestions on what to look at next would be appreciated.

 

 

 

Needs a manifold gauge hooked up and the pressures read.

 

If you don't have one, time to take it to a shop and have it diagnosed.  

[GMCustomerService]

Thanks for bringing your HVAC concerns to our attention. For further assistance, please fill out the form at https://s.gmc.com/support-request with all pertinent details so your concerns get routed properly. Kindly include your username along with additional details regarding your truck's AC concerns.

[B07]

On 7/20/2026 at 5:37 PM, GMCustomerService said:

Thanks for bringing your HVAC concerns to our attention. For further assistance, please fill out the form at https://s.gmc.com/support-request with all pertinent details so your concerns get routed properly. Kindly include your username along with additional details regarding your truck's AC concerns.

I’m working on a 2007.5 Silverado and the dealer said I needed the canister vent solenoid/service kit. 
they couldn’t tell me which one I needed as there were two styles. Not willing to help as I told them I’d have to do the repairs myself due to cost of labor and parts. 

VIN#3GCEC13J47G518531

this is the photos they were showing me. I don’t know which kit I need. They didn’t share the part numbers as I feel they were upset that I didn’t want to pay almost $1,000 for repairing it. 

[carkhz316]

6 hours ago, B07 said:

I’m working on a 2007.5 Silverado and the dealer said I needed the canister vent solenoid/service kit. 
they couldn’t tell me which one I needed as there were two styles. Not willing to help as I told them I’d have to do the repairs myself due to cost of labor and parts. 

VIN#3GCEC13J47G518531

this is the photos they were showing me. I don’t know which kit I need. They didn’t share the part numbers as I feel they were upset that I didn’t want to pay almost $1,000 for repairing it. 

Lol, now I know this is a bot. Go away.

[carkhz316]

Your refrigerant is low. Your symptoms all highlight this. Whether you have an actual leak or have just lost the original charge over the years (about .2-.3 oz per year decay is a thing) remains to be seen. You can connect a gauge set to verify, but you'll really need to evacuate, recharge and monitor for a leak.

[Fishbones]

Yah, I found a leak on the condenser, replaced that and the other replacement parts, re-charged, good to go. thank you.

[B07]

Bots post VIN numbers? That was meant for the GMCustomerService since they don't allow direct messaging.

Thanks for playing