Air not coming only at random from vent or dash?

Tiny
BROOKSIE77K3
  • MEMBER
  • 2002 CHEVROLET TAHOE
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 260,000 MILES
The A/C clutch is out so I leave A/C off and this winter while I had it on heat my front vents and front defrost blow little air when on any setting. I leave it on high because once in a blue moon not often the air will turn on and then turn off. I've replaced the blower motor and resistor as well as the blend door. I'm starting to think the ground wire but don't know full where to look when looking at the diagram in the book to vehicle. Also, when on defrost random times as well I'll hear a noise under the hood and once I turn off defrost it stops. Now do I have two blend doors because I also found another on the driver side the one I replaced was more on the passenger side. Any help would be great. You can hear it change when going from defrost to floor or face vents.
Monday, March 27th, 2023 AT 10:34 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,512 POSTS
So, when you are in the defrost mode the compressor will run, I would unplug the A/C clutch to stop the operation. You are correct on the ground wire which can cause problems. To confirm the bad ground, use a test light and probe the black wire when the blower is not working and if it lights up the ground is bad.

Here is a guide to help:

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

This guide may help as well:

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

I have included the blower motor wiring diagrams so you can see how the system works. Check out the images (below). Please let us know what happens.

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Monday, March 27th, 2023 AT 11:45 AM

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