Iam stumped! help me diagnose an interior noise

[RossT]

Ok, this one has me stumped. My truck is amost a year old. 2003 1500HD 6.0. For about the last 3 months I have been getting this strange constant sound from behind tach/speedo cluster. I can best describe it as a constant hollow humming sound. Here is what I have noticed so far:

 

1. The sound is always present and you hear it at idle or when driving slowly.

 

2. You can not hear it from the engine compartment side. Only present from inside.

 

3. Increasing the RPM at idle has no effect on it. It does not change at all with rpm

 

4. I have messed with all possable settings of the HVAC and nothing will make the

sound change.

 

5. I have heard of some people with trapped air in the cooling system causing

strange sounds from behind the glove box. I did attempt to do the standard

bleeding of the cooling system by letting the truck warm up with the cap off

the surge tank. I did get some bubble out of the cooling sytem but not much.

I did this three times, and no change on my noise from behind the dash.

 

6. I also notice that the noise is slightly present on start up and get lauder as the

truck warms up.

 

7. It has nothing to do with the radio/speakers either.

 

So what do you guys think? any ideas??

 

Thanks for any input you have.

[GMCTech]

It is the litle drive motor that controls the position of the tach.

 

The only way to verify it is to sweep the gauges with a scan tool that has that capability. You'll hear that same hum for the couple moments that the gauge sweeps.

 

It should be covered under warranty, but you'll need to replace the IPC - Instrument Panel Cluster. I've replaced at least 1/2 dozen for this very concern.

 

Hope this helps.

[RossT]

Thank you mr. gmtech. I now have some good info to give to my dealer to check out.

 

That very well could be it, cause I know when the truck is turned on and off, there is alot of chater from the same location for a brief moment.

 

Thanks again.