I have a 1998 GMC Jimmy SLE. It has the manual cold/hot dial, not the automatic temperature control. The AC was not as cold as usual. Checked the AC system and all looks good. Driving to work this 70 degree morning with the dash vents bringing in outside air and the cold/hot dial all the way to cold, the air coming through the vents felt slightly heated. Could the system be added heated air to the outside air or the AC when the cold/hot dial is all the way to cold? Could it be a bad electronic dial or a bad blend door system? Please help. Thanks.

 

It could be a problem with the blend door, or it could be that the A/C system is low on charge. Is the clutch cycling frequently, staying on for just a few seconds?

 

Had an expert look at the AC. Pressures are good and the compressor stays on. He said AC good. We think the blend door is letting a little air from the heater core into vent system even when the cold/hot dial is all the way set to cold. What do you think I should try first? Thanks.

 

I'm not that familiar with the system so I can't really give you specifics, but you should figure out which is the blend door and make sure it's moving all the way. One of those borescope-type cameras that connects to your phone can be helpful.

 

* Moved to '2nd Gen Tech' *

 

The blend door actuator can be changed from the passenger side footwell. You'll need one of these:

 

https://blazerforum.com/forum/articl...ferrerid=22431

 

Search for threads on the subject from Christine 208, she discusses this topic extensively with photos.

George