Normal to hear vacume sound in AC controls? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ScottH** · 06-01-2011, 02:04 PM

Was working on my 84 the other day and noticed when the engine is running I am hearing what sounds like a vacume leak coming from the AC/heater controls. Can anyone tell me if that is normal or do I have a leak somewhere?

Any info is much appreciated.

Thanks
Scott

tucsonjwt · 06-01-2011, 02:37 PM

I have never heard a vacuum leak from A/C controls, but I do hear the vacuum actuators when they engage/disengage and occasionally hear a hiss when the A/C starts up. But if the A/C is functioning properly I would not be concerned about it.

Malo83 · 06-01-2011, 03:22 PM

Normal

85gmcguy · 06-01-2011, 04:55 PM

Try all of your heater/defrost/AC/vent functions. Could be an actuator (usually the blend door) going kaput. If it fails, no defrost.

**ScottH** · 06-01-2011, 06:51 PM

thanks guys. I tried it on all settings, seems to be noticeable when in off position and a/c on, if heat or defrost r on I dont hear it. Defrosters r working but not very strong it seems.

CaliDude76 · 06-02-2011, 08:28 PM

Quote:

Originally Posted by ScottH

thanks guys. I tried it on all settings, seems to be noticeable when in off position and a/c on, if heat or defrost r on I dont hear it. Defrosters r working but not very strong it seems.

Mine does that too... but if I wiggle it to the MAX, and back to OFF, the hiss stops.. mechanisms back there prolly just getting old and loose. It happens

**ScottH** · 06-05-2011, 11:02 PM

Swapped out the controller tonight with another I had in my parts stash and the vacume sound is gone. Also it seems that the defrosters r noticeable stronger. No way to see if there is any change in AC since it isnt working yet. Just wanted to update everyone.

Scott

06-01-2011, 02:04 PM	#1
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,193	Normal to hear vacume sound in AC controls? Was working on my 84 the other day and noticed when the engine is running I am hearing what sounds like a vacume leak coming from the AC/heater controls. Can anyone tell me if that is normal or do I have a leak somewhere? Any info is much appreciated. Thanks Scott __________________ 1963 C10 swb fleetside 1966 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

06-01-2011, 02:37 PM	#2
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,198	Re: Normal to hear vacume sound in AC controls? I have never heard a vacuum leak from A/C controls, but I do hear the vacuum actuators when they engage/disengage and occasionally hear a hiss when the A/C starts up. But if the A/C is functioning properly I would not be concerned about it.

06-01-2011, 03:22 PM	#3
Malo83 Cruzzzn' Vet Join Date: Jan 2005 Location: Porterville,Ca. Posts: 1,918	Re: Normal to hear vacume sound in AC controls? Normal

06-01-2011, 04:55 PM	#4
85gmcguy Plays with trucks Join Date: Sep 2003 Location: Asheville, NC Posts: 433	Re: Normal to hear vacume sound in AC controls? Try all of your heater/defrost/AC/vent functions. Could be an actuator (usually the blend door) going kaput. If it fails, no defrost. __________________ Gary My Dad's Old Truck 1985

06-01-2011, 06:51 PM	#5
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,193	Re: Normal to hear vacume sound in AC controls? thanks guys. I tried it on all settings, seems to be noticeable when in off position and a/c on, if heat or defrost r on I dont hear it. Defrosters r working but not very strong it seems. __________________ 1963 C10 swb fleetside 1966 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

06-05-2011, 11:02 PM	#7
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,193	Re: Normal to hear vacume sound in AC controls? Swapped out the controller tonight with another I had in my parts stash and the vacume sound is gone. Also it seems that the defrosters r noticeable stronger. No way to see if there is any change in AC since it isnt working yet. Just wanted to update everyone. Scott __________________ 1963 C10 swb fleetside 1966 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon



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