just wondering if anyone else notices a slight hissing noise from what seems to be in the dash. Is there anything that operates off of vaccum in there?

 

Orifice tube! Turn your a/c off and see if it goes away..

 

There is actually a service bulletin saying it's normal..

03-05 Chevrolet/GMC/Cadillac All Full Size Trucks and Utilities Hiss Noise from Dash with AC On - kw HVAC idle blower compressor line hose #PIT3344 - (Jan 4, 2005)
03 - 05 Chevrolet/GMC/Cadillac All Full Size Trucks and Utilities Hiss Noise from Dash with AC On
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:
Customers may comment of a hiss noise coming from the dash area with the A/C on. The noise can come and go or change intensity depending on A/C system loads (outside temp, engine RPMs, humidity, etc.)

Recommendation/Instructions:
The noise is normally only heard while stopped with blower on low and radio off. The noise is coming from the A/C orifice tube and is normal. No repairs should be made.

.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Models:
(03-05 Chevrolet All Full Size Trucks and Utilities) and (03-05 GMC All Full Size Trucks and Utilities) and (03-04 Cadillac All Full Size Utilities)

 

Hey, thanks for the 411

 

anyone else hear this?

 

I didnt notice it with my 4.8, but there is a deffinate hiss after I swapped in the LS1. I havent been able to track down where it is coming from yet.

 

if you still have the factory radio theres a cooling fan in the back of it. when ever the radio gets to a certain temp that fan kicks on. i hear that making a noise sometimes. maybe thats it?

 

It isn't when the AC is on, it is when it is on recirculate. Turn the recirculation on while driving down the highway, and then turn it off and wait about 5 sec while driving down the highway. It will go away. There isn't a seal at all on that door that opens and closes. One of the guys on the silverado ss board fixed his, but I wasn't able to get any pics from him.

Aaron

 

Turn the friggen radio up you sissy.

 

Grippy