2007 Silverado classic Cooling fan running

sefiroxx · February 8, 2020

Yes, get a set of a.c. Guages (not the cheap low side can adapter). Connect with system off. Hi and Lowell should match in the 50-100 range (depends on air temp). System on, lo 30-40 and hi 200-300.

Dennis Ellert · February 8, 2020

Thank you for the reply. I think you are right, I"ll plug the pressure switch back in and start over again, however I am not sure if my scanner can provide the info needed and I'm not sure I am a good enough scanner user to get the info I need . Also I am leaving for a ski trip to Montana next week and wont get back to that truck until the week after that. I will revisit this site and report what I learn after I get a chance to work on the truck again, but probably won;t be until close to the end of the month. I very much want to thank you for your ongoing help, you have steered me in a different direction. I will report what I learn. Thanks again Dennis.

rt66er · June 19, 2021

Did you get this figured out? I have a similar problem (2011 GMC Sierra). If I turn on the A/C shortly after a cold (or hot) start, the high speed fan is triggered after ~30 seconds, regardless of coolant temperature. It will run high speed for several minutes before eventually reverting to low speed (correct) operation and when running at high speed, the battery voltage will drop significantly. In addition, the fans will continue to run high speed even at 60 mph, but will eventually switch off as they should. Refrigerant charge/pressure has been verified correct. I also replaced the high pressure A/C switch with no change in operation. Any help would very much be appreciated.

Raphael · September 19

Did anyone figure out how to fix this issue?

I have a 2007 Silverado 4.8 doing the same. I was told it needed a compressor. At this point I’m tired of throwing parts at it per mechanics suggestions.
New compressor, condenser, orifice tube, hi and low pressure switches also took to Firestone to redo the refrigerant (pull vacuum and refill), new ACDelco water pump with thermostat, ACDelco temperature sensor. And the cooling fans are on high all the time and the AC will not turn on.