On my 2004 Envoy XL, there is a knocking or tapping sound for 15 to 25 seconds, after starting the engine. It does not happen all the time, but mostly on cold start. This sound is coming from the Passenger side rear of the SUV, behind the 3rd seat and underneath the side window, and behind the plastic panel. I can feel (barely) the knock when touching this area.
Another issue (not sure if related) is that I can practically feel no air (Hot or Cold) coming from the front panel. Defrost works fine, so does the Floor vents. However the front vents do not blow air. A search on the web pointed to a defect with the Actuator or one that needs to be recalibrated after a battery disconnect. I pulled & replaced the HVAC-B fuse (10 amp) and it did the trick but stopped working next time I restarted the truck. BTW: I pulled the fuse while the truck was running.
thanks in advance, sky
Another issue (not sure if related) is that I can practically feel no air (Hot or Cold) coming from the front panel. Defrost works fine, so does the Floor vents. However the front vents do not blow air. A search on the web pointed to a defect with the Actuator or one that needs to be recalibrated after a battery disconnect. I pulled & replaced the HVAC-B fuse (10 amp) and it did the trick but stopped working next time I restarted the truck. BTW: I pulled the fuse while the truck was running.
thanks in advance, sky