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Heater Hiss
#787435 January 17th 2022 6:16 am
Joined: Sep 2020
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Fly_Low Offline OP
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I wanted to see if it’s normal on a 80’s G20 for there to be a hissing sound coming from the heater controls when you turn the van off and after the heat has been running for a while. If i move the slider from “heat” to “off”, it stops right away. Otherwise, it hisses until it peters out. Had the heater core replaced early in the year, but then never really had to use the heater! Wanted to make sure it’s a normal sound. Thanks so much

Re: Heater Hiss
Fly_Low #787451 January 17th 2022 1:14 pm
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veteran
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Heyo .Welcome to the Site. It sounds like vacuum bleeding off. IDK if that's normal, a problem, a leak? Or not. Miy 90 G30 doesn't do it.

You can check lines and vacuum motors with those vacumm pump guns that they sell at HF for brake bleeding. If you need me to, I can crack a book if you need parts, service, or diagram info, but if a vacuum guage on the motor doesn't indicate a leak under the hood issue, And if the controls and heater all function normally?

Could mebe be a hose, or component, but if under the dash? I hope not. Gday!


"Who New? Blue"
1990 Chevy G30 454
Church Van, maternity division

"DogVan"
1988 Dodge B250

"Cabin Cruiser"
'94 Dodge B350 www.xplorermotorhome.com/
Xplorer MH model 230 230 hp MPI 360 LA Wedgy OD auto

Old vans are getting pricey!
Re: Heater Hiss
Fly_Low #787474 January 17th 2022 10:26 pm
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old hand
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I would pull the heater/A/C controls out and check the vacumn lines. One is either just loose or maybe cracked.....those lines get pretty brittle over the years.


Recently purchased (10-2021) a 1991 Chevy G-20 “Shorty”. Past vans are a 1976 Chevy G-10 (purchased new in 1976 & sold in 1995). A 1978 Chevy G-20 Shorty purchased in 2010 and sold in 2015.
Re: Heater Hiss
Fly_Low #787479 January 18th 2022 5:26 am
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Fly_Low Offline OP
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Ugh, figured it was some kind of vacuum issue. Wanted to ask first before diving in there. Thanks for the replies

Re: Heater Hiss
Fly_Low #787482 January 18th 2022 10:57 am
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carpal tunnel
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Pull the doghouse cover (leave the doghouse in place) and you may be able to tell which side the hiss is coming from, maybe tell if the hiss is from the controls side or the heater side. I like to use a piece of hose as a stethoscope to help track down leaks....

Just thinking out loud here.

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