GMC C1500 Dash Clicking Sound

GMC C1500
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MROMER
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  • 2 POSTS

Whenever I turn the ignition key to the position where the radio comes on, I hear a clicking/thumping sound coming from the area of the blower motor housing under the dash on the passenger side. The sound lasts for about 10 seconds and then stops. When I turn the truck off, it happens again for about 10 seconds. The problem didn't occur often until I had the AC system recharged lately. What do you think the problem is? If I need to replace the blower motor, how can I remove the plasting cowling in front of it without cutting it out?
Apr 5, 2006 at 1:12 PM
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MROMER
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After feeling around underneath the blower and recreating the problem, I noticed that there is a white plastic vent with a black plastic grate that can be seen if you lay down on the passenger floor mat and look up towards the blower. If you push up firmly on the vent, the clicking noise will stop. I'm not sure if it's a vibration problem or what. I wedged the vent partly closed, and that stopped the noise. I also checked to make sure that when I unwedged the vent after about 10 seconds (when the sound normally stops) that it didn't start back (i.e. I wanted to make sure that I wasn't holding up a motor, which might heat up and cause future problems).

Not a scientific fix, but a fix nonetheless....
Apr 8, 2006 at 12:57 PM
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GENO51769
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I'm having the same exact problem with my 91 Chevy K1500. It has been driving me nutty. I can't believe it is that simple to fix. I figured I would be taking the whole blower out. Now granted I haven't yet tried what you posted but the symptoms sounds the same.
Aug 9, 2006 at 4:31 AM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Sounds like the blend door actuator is bad. This is a common issue with these GM trucks

See the guide below on how to replace it

https://www.2carpros.com/articles/replace-blend-door-motor

Here's a video

https://youtu.be/Eqf-H3COtSo
Mar 4, 2019 at 10:41 AM
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Suggested Repair

Replace the blend door actuator (blend door motor), a common failure on these GM trucks that can cause the brief clicking or thumping under the dash.

Conversation Summary

The owner of a GMC C1500 hears a clicking or thumping from the passenger-side blower housing for about 10 seconds when the key is turned to the radio position and again when the truck is shut off. It became more frequent after an A/C recharge. Pushing up on a plastic vent under the blower stopped the noise, and wedging the vent partly closed was used as a temporary fix. Another owner reported the same symptom on a 1991 Chevy K1500. The expert said the blend door actuator is likely bad and pointed to a replacement guide and video.

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