Heater problems
Thread Starter
Instructor
Joined: Jan 2017
Posts: 175
Likes: 14
Heater problems
I have a 1974 corvette and I'm having trouble with the heat. My heat suddenly stopped working and i need to replace the water shut off valve. Is the valve located in the heater box near the core its self? I was driving the car with the heater running and it suddenly started blowing cold air out.
Race Director
Joined: Mar 2017
Posts: 11,944
Likes: 4,506
From: Virginia
Make sure you don't have a leak first!
Do you have AC? I thought only 75 and up had water shut-off valves stock, and only with AC. If stock, or a stock addition, it would look like this, and be behind the passenger wheel well.
http://www.zip-corvette.com/75-79e-a...off-valve.html
It is vacuum controlled, and the vacuum hose may have fallen off, or cracked and broken (it is plastic and brittle).
If you can, get a copy of the AIM for your car, and see what's in your '74. Unless a PO added it, I doubt you have a water valve. You may have had the damper door close due to a vacuum leak, however.
Do you have AC? I thought only 75 and up had water shut-off valves stock, and only with AC. If stock, or a stock addition, it would look like this, and be behind the passenger wheel well.
http://www.zip-corvette.com/75-79e-a...off-valve.html
It is vacuum controlled, and the vacuum hose may have fallen off, or cracked and broken (it is plastic and brittle).
If you can, get a copy of the AIM for your car, and see what's in your '74. Unless a PO added it, I doubt you have a water valve. You may have had the damper door close due to a vacuum leak, however.
Le Mans Master
Joined: Feb 2001
Posts: 6,317
Likes: 291
From: Ocala FL
Before you get too involved, take a look around on here at various threads to get an idea of how everything looks and works.
Sometimes what you think is wrong isn't the problem.
Look at this thread.
https://www.corvetteforum.com/forums...right-now.html
First trick, get the car warm to hot, and then feel both heater hoses as close to the firewall as possible. Are they hot?
- if both are, your problem is not the valve.
- if only one is, something is blocked. Valve, heater core, etc.
Feel the bottom of the heater box inside the car near the firewall. Is it hot?
- if it is, then the heater core is working and you aren't getting air through.
- if it isn't, then your heater core must not be working or hot water isn't moving through.
If the heater box is hot but the vents aren't blowing hot air, check all of the following:
- fan blows air
- diverter valve (flapper) by the heater core is closing. Check the pieces on top to see if they are moving it closed.
- check that the cable is actually moving it. Cables can break out of their sheathing down at the console control and not close or fully close the heat diverter.
- check that there are no obstructions in the air passage (mouse nest, squirrel nest, shop rags, etc.)
There are more things it could be but this gets you started.
Sometimes what you think is wrong isn't the problem.
Look at this thread.
https://www.corvetteforum.com/forums...right-now.html
First trick, get the car warm to hot, and then feel both heater hoses as close to the firewall as possible. Are they hot?
- if both are, your problem is not the valve.
- if only one is, something is blocked. Valve, heater core, etc.
Feel the bottom of the heater box inside the car near the firewall. Is it hot?
- if it is, then the heater core is working and you aren't getting air through.
- if it isn't, then your heater core must not be working or hot water isn't moving through.
If the heater box is hot but the vents aren't blowing hot air, check all of the following:
- fan blows air
- diverter valve (flapper) by the heater core is closing. Check the pieces on top to see if they are moving it closed.
- check that the cable is actually moving it. Cables can break out of their sheathing down at the console control and not close or fully close the heat diverter.
- check that there are no obstructions in the air passage (mouse nest, squirrel nest, shop rags, etc.)
There are more things it could be but this gets you started.
Last edited by Procrastination Racing; Oct 11, 2017 at 08:59 PM.
Thread Starter
Instructor
Joined: Jan 2017
Posts: 175
Likes: 14
Make sure you don't have a leak first!
Do you have AC? I thought only 75 and up had water shut-off valves stock, and only with AC. If stock, or a stock addition, it would look like this, and be behind the passenger wheel well.
http://www.zip-corvette.com/75-79e-a...off-valve.html
It is vacuum controlled, and the vacuum hose may have fallen off, or cracked and broken (it is plastic and brittle).
If you can, get a copy of the AIM for your car, and see what's in your '74. Unless a PO added it, I doubt you have a water valve. You may have had the damper door close due to a vacuum leak, however.
Do you have AC? I thought only 75 and up had water shut-off valves stock, and only with AC. If stock, or a stock addition, it would look like this, and be behind the passenger wheel well.
http://www.zip-corvette.com/75-79e-a...off-valve.html
It is vacuum controlled, and the vacuum hose may have fallen off, or cracked and broken (it is plastic and brittle).
If you can, get a copy of the AIM for your car, and see what's in your '74. Unless a PO added it, I doubt you have a water valve. You may have had the damper door close due to a vacuum leak, however.
