C3 Corvette Forum
Tech/Performance/Info >> Interior Information/Questions >> Heat/AC Issue

Message started by Miketw on May 26th, 2016 at 9:58am

Title: Heat/AC Issue
Post by Miketw on May 26th, 2016 at 9:58am
Hi Guys. I have a 1977 Corvette which blows heat all the time, even when the lever is moved to cold. Any ideas on where to even start to run down this issue?


Title: Re: Heat/AC Issue
Post by Artsvettes on May 26th, 2016 at 11:28am
The vacuum switch that is mounted on the heater box would be my first guess. The whole vacuum system is critical for the heat and a/c to function properly..........jack

Title: Re: Heat/AC Issue
Post by Knotacare on May 27th, 2016 at 8:03am
I added a cutoff valve on my 77 because hot water is always flowing through the heater on theses cars. Just open it up once a month or so in the summer to keep it flushed.  This really helps in these cars with the stock heaters.
Alan [smiley=beer.gif]

Title: Re: Heat/AC Issue
Post by fire_mouth on Jun 30th, 2020 at 8:18am
Hello. I am new to the forum. I just bought a 79 vette. Someone has replaced the L-82 engine with a '79 305. Some things are not working:

-All air output from fan comes to floor, no matter what I select with the control. It always comes out the bottom. I assume some vacuum controlled system changes fan output to defrost, etc.. but where do I begin looking?

- Rear window defogger does not light up. I do not know if it is working or even hooked up.

-  No fob to lock/unlock doors. How can I find out if there is a fob to lock/unlock doors on this car?

- Gear selector missing. Don't see what gear I'm in.

- Windows go up/down at different speeds.

- Driver side looks window control looks like it is scratching glass. I want to tint the side windows but need to fix this first. Any tips?

Thanks in advance!


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