Blower works but blend door or temperature selection not working

THAT_GUYYOUALLKNOW

MEMBER
2000 CHEVROLET SILVERADO
4.8L
V8
4WD
AUTOMATIC
195,000 MILES

So, I got in my truck to drive to work today. As I'm driving, I realize that even though my temperature sending unit says my truck is warm it's still blowing cold air. I have no control over the blend door, or the temperature control. But the fan acts normal. I have been at work all day and have found virtually nothing to explain this. I'm off at 11:30pm. It's 9:00pm now. The temperature outside is 13°F and my windshield is frosted. Is there a fuse that could be blown or did the head go bad while I drove? Oh yeah, one last thing, the recirculation button didn't have a light as it normally does. Thanks in advance.

Thursday, January 6th, 2022 AT 5:58 PM

3 Replies

JACOBANDNICKOLAS

MECHANIC
110,144 POSTS

Hi,

There is one fuse that controls the blend air doors and the recirculation doors. Since the light isn't on, check that first. If the fuse is good, then I would suggest checking for continuity to ground (black wire) at one of the locations. Both of these circuits have a common ground.

As far as the fuse, first confirm it is good. If it is, make sure there is power to and from it. See this link:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

I attached pics of the wiring schematic below. You can use it as a reference. Also, here is a link you may find helpful:

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

Let me know what you find.

Take care,

Joe

See pics below.

Images (Click to make bigger)

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Thursday, January 6th, 2022 AT 6:55 PM

THAT_GUYYOUALLKNOW

MEMBER
2 POSTS

So, I went outside and started pulling fuses, anything remotely connected to the climate control system. All of them were still intact. Because my hands were numb, I grabbed the book from the glove box and went back inside for a minute to warm up. There was one listed I missed. It was in the same circuit as the radio. Instead of popping the hood I decided to just check the radio. Well, everything worked as it should. The only thing I can think of is one of the fuses was corroded. The act of pulling and replacing must have cleaned it enough to allow contact. So, gents if you have this problem good news it's a fuse not the controller, bad news I have no idea which one it was. Hope this helps someone else, along the road of life.

Happy trails
THAT_GUYYOUALLKNOW

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Thursday, January 6th, 2022 AT 7:19 PM

JACOBANDNICKOLAS

MECHANIC
110,144 POSTS

Hi,

Thanks for the update, and I'm glad it's working. If I had to guess, I would say the HVAC 1 fuse. Certainly, corrosion can cause problems, especially when it gets cold.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe

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Thursday, January 6th, 2022 AT 9:08 PM