heat on all the time
Thread Starter
Navigator
Joined: Dec 2006
Posts: 9
Likes: 0
heat on all the time
I've owned this car [ 77 corvette ] for almost 30 years and I have always had a problem with heat coming from the heater even when the temp handle is positioned in the cold temp position and turned off.Is this a common problem for this car[C-3]?? Is there a tip[ or list of tips ] for troubleshooting this problem Also while I'm looking for help,I had a heater relay switch go bad about 10 years ago and could't find one locally so I took the old one in to the NAPA store and matched one up.It was a camaro switch
- 1983 I think And since I don't drive this car but maybe a hundred miles a year, and I don't remember if this problem has always been like this but on high the blower motor dosen't put out a lot of air- like its running on half speed. Is this because of the camaro relay switch or what?????
Thanks for your time
Ken
chantil@adelphia.net
- 1983 I think And since I don't drive this car but maybe a hundred miles a year, and I don't remember if this problem has always been like this but on high the blower motor dosen't put out a lot of air- like its running on half speed. Is this because of the camaro relay switch or what?????
Thanks for your time
Ken
chantil@adelphia.net
Burning Brakes
Joined: Jul 2008
Posts: 876
Likes: 0
From: Canastota Ny
i had just the opposite on my 79. the heat would not come on. turned out it was the heater valve in line of the heater core. it was stuck closed hense no heat. most likely if you have one that is stuck open always letting coolant flow through and wah-la! heat..
Drifting
Joined: Jan 2004
Posts: 1,991
Likes: 3
From: Piscataway NJ
Is the control valve on the heater hose working?
Is it getiing and vacuum?
If not there is a vac. switch on to of the heater box behind the dash. Don't ask how I know. But follow this it works
http://1-4u-computer-graphics.com/ya...num=1145474576
Is it getiing and vacuum?
If not there is a vac. switch on to of the heater box behind the dash. Don't ask how I know. But follow this it works
http://1-4u-computer-graphics.com/ya...num=1145474576
Racer
Joined: Mar 2008
Posts: 428
Likes: 0
Is the control valve on the heater hose working?
Is it getiing and vacuum?
If not there is a vac. switch on to of the heater box behind the dash. Don't ask how I know. But follow this it works
http://1-4u-computer-graphics.com/ya...num=1145474576
Is it getiing and vacuum?
If not there is a vac. switch on to of the heater box behind the dash. Don't ask how I know. But follow this it works
http://1-4u-computer-graphics.com/ya...num=1145474576
Drifting
Joined: Jan 2004
Posts: 1,991
Likes: 3
From: Piscataway NJ
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
There is not guarantee that shutting off the water to the heater will fix your problem. Why? Because you haven't really determined the cause... you just know that there is heat coming out the vents. That heat could be from the engine compartment via leaking into the fresh-air entry at the cowl. I'm just suggesting that there are other possibilities and that you need to do more diagnoses before you start 'fixing' things. [ie., use a big vise-grip to squeeze off the flow in the 'to-heater' line, then drive the car to see if it still gets hot...or not.] If that is the problem you could put a shut-off valve in that line...or just plug-off the heater, if you never really use it.
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Thread Starter
Navigator
Joined: Dec 2006
Posts: 9
Likes: 0
I unplugged the fan relay and this made a slight difference in the amount of heat coming thru the lower vent. I’m going to block off the heater core and see if the heat is coming from the engine compartment. I'm beginning to think that the distribution assembly is where the problem might be, which the last place I wanted to get into ...
More to do I guess
Thanks again
Ken
More to do I guess
Thanks again
Ken
Safety Car
Joined: Oct 2007
Posts: 4,383
Likes: 1,753
From: Seattle Area Washington
I bought that vacuum switch from Ecklers. I had tried different vendors hoping that the spring rate would be lighter but no luck. If you use the spring that comes with the new reproduction vacuum valves there is a good chance that the heater control cable will return past the cold position because of the spring rate of the new valves. That’s when I though of a way to replace the spring in the new valve with the original spring.
There are a couple reasons I would never install a manual valve in the heater hose line.
1. Using a manual globe, ball, or gate valve IMO looks terrible.
2. Without remembering to open the manual valve for any extended period of time will let the heater core dry out and that is when the core will start to decompose from the inside out. You always want to keep the core flooded with coolant.
After fixing the spring issue in the vacuum valve there were other reasons why the heat was entering the cabin. This is also what I found when I dug a little deeper into my interior heat problem.
The vacuum line entering through firewall rubber grommet on the interior side had two little holes in it from chafing (circled red). Even with the two pin holes I had 11 in. vacuum at the inline heater hose vacuum valve, not enough to close it all the way.
There are a couple reasons I would never install a manual valve in the heater hose line.
1. Using a manual globe, ball, or gate valve IMO looks terrible.
2. Without remembering to open the manual valve for any extended period of time will let the heater core dry out and that is when the core will start to decompose from the inside out. You always want to keep the core flooded with coolant.
After fixing the spring issue in the vacuum valve there were other reasons why the heat was entering the cabin. This is also what I found when I dug a little deeper into my interior heat problem.
The vacuum line entering through firewall rubber grommet on the interior side had two little holes in it from chafing (circled red). Even with the two pin holes I had 11 in. vacuum at the inline heater hose vacuum valve, not enough to close it all the way.
Last edited by bmotojoe; Aug 26, 2008 at 08:34 AM.
Drifting
Joined: Apr 2008
Posts: 1,305
Likes: 2
From: Lewisburg WV
thegazman
I had the same problem with my 79. The strong spring in the heater control valve would push the control cable to slightly open positon due to the vibration of driving causing the hot water valve to open and also open the heater door. I would have to push the heat control valve to cold every five minutes. I purchased an electric control valve conversion kit from Corvette Clinic, Sanford, Florida and have not had a problem since.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Also check the fresh air flap under the RH fender. You can reach it through the hole at the rear of the hood down inside the cowl. The vacuum line to this flap was often pinched when installed at the factory causing it not to close.