Blower Motor, revving noise

[Aonghus]

This is a little hard to describe but I'll give her a go...

2004 Tahoe Z71, 5.3...need any other info?

When the blower motor (heater/AC) is turned on I get a fairly loud revving sound while accelerating, or revving the engine while stopped. The sound changes pitch with the RPM's of the engine but does not change pitch with the speed of the blower. It does not appear to matter whether I have it set to hot or cold or the AC switch on or any of the airflow position settings. I do not get the same sound with the rear air on. The noise can be heard from both inside and outside the vehicle and appears to be coming from the firewall area...

I had a bad blower motor in my Jeep years ago but the "bad sound" changed with different speed settings for blower, NOT with the RPM's of the engine. This makes me think of an electrical problem somewhere (ie, faulty ground??) that is somehow feeding engine noise back into the system.

I dunno, I'm a little stumped. Any ideas? Where should I start looking?

 

[blueflamed03]

sounds like a grounding issue.

 

[Aonghus]

That's what I was thinking....do you have any suggestions as to where to start looking? Do you think it is a ground for the blower or one of the big grounding cables from the engine to the firewall? Or something else?

We just got his vehicle a couple months ago so I'm not all that familiar with it yet. First Chevy we have owned.

Thanks for the reply!

 

[nickolas]

This is a little hard to describe but I'll give her a go...

2004 Tahoe Z71, 5.3...need any other info?

When the blower motor (heater/AC) is turned on I get a fairly loud revving sound while accelerating, or revving the engine while stopped. The sound changes pitch with the RPM's of the engine but does not change pitch with the speed of the blower. It does not appear to matter whether I have it set to hot or cold or the AC switch on or any of the airflow position settings. I do not get the same sound with the rear air on. The noise can be heard from both inside and outside the vehicle and appears to be coming from the firewall area...

I had a bad blower motor in my Jeep years ago but the "bad sound" changed with different speed settings for blower, NOT with the RPM's of the engine. This makes me think of an electrical problem somewhere (ie, faulty ground??) that is somehow feeding engine noise back into the system.

I dunno, I'm a little stumped. Any ideas? Where should I start looking?

My fix was unplug the valve. no a/c but with high gas prices never used it anyway.

Radio off I assume. Have you listened carefully at each speaker in your sound system (radio off)? Is it possible a speaker wire is in contact with an electrical power source related to the blower. I'd also suggest disconnecting the alternator for a few seconds and see if the sound goes away.