Heater always heating!
Thread Starter
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Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
Heater always heating!
Hello again. It seems that I cannot turn off the heater in my truck. Whenever I switch the heater control **** to "Cool," it still puts out air thats just as hot as if I have it on "Warm." I have already tried replacing the valve that controls coolant flow into the heater core. Could it be heat coming off the headers? Where does a 1970 F-100 draw air in from anyway? (no "through the rust holes" jokes... 
) Any ideas? Would it be good to put a valve on the return hose from the heater core too?
) Any ideas? Would it be good to put a valve on the return hose from the heater core too?
Posting Guru
Joined: Aug 2002
Posts: 1,493
Likes: 1
From: Great NW
Heater always heating!
Are you sure that your linkage that goes from your dash controls to the heater box are functioning OK?
It is possible that a cable came unhooked and is not operating the controls...
It is possible that a cable came unhooked and is not operating the controls...
Posting Guru
Joined: Aug 2002
Posts: 1,493
Likes: 1
From: Great NW
Heater always heating!
Just a thought...
When I recently replaced the heater core in my '74, I found out that someone who had replaced it before me, hogged out the interior of my heater box to accomodate one of the larger "Extra capacity" cores. It worked fine until I went in to replace that core and discovered that the new (smaller) heater core did not seal up properly against the moving parts in my heater box.
I suppose something similar could be happening with yours (the linkage & internal flappers not fully sealing off the core from the air flow, causing heat to slip by and into the cabin.
When I recently replaced the heater core in my '74, I found out that someone who had replaced it before me, hogged out the interior of my heater box to accomodate one of the larger "Extra capacity" cores. It worked fine until I went in to replace that core and discovered that the new (smaller) heater core did not seal up properly against the moving parts in my heater box.
I suppose something similar could be happening with yours (the linkage & internal flappers not fully sealing off the core from the air flow, causing heat to slip by and into the cabin.
Thread Starter
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Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
Heater always heating!
Could be. I'm gonna be re-doing it all anyway, I just got back from the junkyard with a new-to-me dealer installed A/C system... 
Hopefully I can get it installed, correctly, within the next week. I'll let everyone know how it turns out.
Hopefully I can get it installed, correctly, within the next week. I'll let everyone know how it turns out.
