Heater won't turn off!

[nj7000]

During the summer I still get hot air blowing out of the vents by my feet, even though the fan is turned off and/or it's turned to cool. I know this topic has been addressed previously, but I can't seem to find the thread. Could someone give me some advice or point me in the right direction? thanks!

 

[76okievette]

NJ, I have the same thing on my 1976, I was told its a short in the fan motor circuit. I can turn the heater to the off postion and cycle the fan switch and some times this stops the hot air. I have not gotten any further into than that but would be real interested in any thing you find out. Its not enough in these cars with out have the heater blowing during the summer.

 

[76okievette]

Man that last sentence was a mess, I meant to say, Its HOT enough in these car's with out having the heater running in the summer time.

 

[Ryan]

Hi,


Your problem may be a very easy fix. Between the hose that comes from the waterpump and goes to the heater core, there is a heater valve with a vacuum hose. That valve may be not functioning anymore. You can try to fit a valve that you can manualy close in the summer. That will stop the hot water from circulating through the heater core.

Hope this will help.

Ryan

 

[nj7000]

Ryan, the valve you're talking about, is that the heater control valve. The one that's small with a round head and an inlet and outlet?

Yeah we get enough heat from the engine and the sun, the last thing we need in the heater going in July.

 

[Tweek]

Good OL chevy astro vent heating system, Ryan has a great tip on checking the valve, but the fan still runs every so little on chevys in those years. I just unplug the power from the fan in the summer, to stop the hot air from blowing. If you turn the key on and listen on the passenger side under the hood you will here it running. Remember though, you need the fan for the air conditioner in the summer also.

 

[Ryan]

yes that's the one. Be sure it's functioning well. There is a vacuum hose going from the valve to the heater/ac control. This vacuum hose may also have a leak.

Cia,

Ryan

 

[Robin7TFour]

HELLO, i can't remember the exact post,but there was a thread recently about disconnecting one wire on the fan relay. this will stop the fan from blowing when the key is on. then you only get the fan whan using the switch.

BUBBA .the roving shade tree

 

[Bob Chadwick]

Just about everything that I have been able to compile from multiple sources on the HVAC system in the C3's.

I have just added a second valve to my heater lines. I was still getting heat out of the vents with the one valve so I added the other. It was a gradual creep, so I figured either the system plastic is getting hot from the exposure to engine heat or the open line on the heater core was transferring enough heat to gradually heat the core.

 

[80convertible]

Here is what I did to cool the car off in the summer living in NC. First, I removed the heater control valve and installed a manual valve. I simply open the valve in the winter and close it in the summer. Works better than anything else including replacing the heater control valve...unless you are in to NCRS stuff. Second, I disconnected the low speed fan wire that keeps the fan running all the time. I still have medium and high speed, but no air blowing when the low speed is selected. These two things really cooled the vette off. Also, make sure all the grommets and any open air passages between the engine compartment and the cabin are sealed.

 

[DDLS3]

The heater control valve on my 81 started leaking coolant through the diaphram. I got a new one from Advance Auto Parts for about $25.00. I had always just accepted the heat from the vents as a C3 thing and lived with it. After I replaced the heater control valve the heat stopped coming from the vents. It is not bad to change, will likely take you an hour or less. The original valve is riveted to the fender. I drilled the rivets out and replaced them with 3/16 pop rivets.

 

[BrianB]

As a new owner I thought this was normal. This forum rocks. I'm printing this thread out now and I'll surely get mine done up when I have time. It's really hot here already.

Thanks

 

[STREETRODS]

thanks again guys. coming back from church this morning , the wife and i were discussing the very same thing. i logged on today to ask this very question.

also, is the whine from the rearend a normal thing or do i need to look further? the fluid is up, but have no idea if posi fluid is in it. will that make in noisy?
thanks again