Let's Check the A/C! 2001 Tahoe

Check the settings. The fan should be at the next to lowest speed. Technically low should be the coldest air but some cars have a barely noticeable flow at the lowest setting, so I tend to use the second position. Verify the fan does run and that you do have airflow at the vent. Center vents should be coldest so when necessary I put a thermometer in a center vent. I can feel by hand this is not cold but I'll put the thermometer in so you can see as well. Set the temperature control to coldest. Select recirculate or max air. This position will take longer to cool the vehicle interior but we are measuring at the vent. Once we are doing a drive later we want to see the vent temp reach at least 50 F once the interior has cooled before it gets a stamp of approval. 

Ok, 120 F seems to verify a non-functioning A/C. 

Turning the temperature control to full heat does get warmer so the temperature blend actuator is capable of moving. 

I'm not testing the heater today so I'm not going to see just how hot it will get. This seems a good time to point out that failed blend actuators is a very common cause of A/C not getting cold. 

Time to check under the hood. We want to verify the A/C compressor belt is present because these are known to lose belts. The belt is fine. The compressor clutch can be turned by hand so the compressor isn't seized. We want to know if the compressor clutch engages when the truck is running with A/C on. It does not. Now if the wiring at the compressor was more accessible I might do an electrical check there at this time but it is not. Following the path of least resistance then we will check the system charge. 

Let's call in the heavy equipment. 

Now I can't swear the blend actuator is 100% and I can't swear we don't need some refrigerant, but I do know we have enough pressure on the system that the compressor clutch should engage and it doesn't. Let's continue. I think, because I'm not yet ready to dig around the compressor harness that we should do our tests at the compressor relay, which actually appears to be disconnected and just laying in position vs pressed into the connectors. 

Apparently someone has removed the relay and did not fully engage on re-install. Now the compressor clutch is engaged. I've reached my target of 50 F at the center vent and we're done. I'm sure that no one will have any idea how that happened. 

Thanks for reading!

Kenny@ggauto.repair