It's Gettin' Hot In Here

[tuned88]

I can't get the heater in my '71 F250 to shut off. The slider control is easily moving the valve in the heater hose inside the engine compartment. The slider selector control changes the air direction from heater to defrost with no problem. But it's always full hot. Any thoughts on the reason for this would be greatly appreciated.

[72BahamaBlue]

When I replaced the heater core and temp. control valve, I couldn't remember which hose to connect to the valve, water pump or intake outlet. Ended up with full heat as you described.
Switched hoses at the core, worked as normal.
The valve itself may fail, allowing enough hot coolant to flow into the core, constant hot.

[michael69]

the valve itself may be bad. They will corrode and rust on the inside and allow the water to keep flowing to heater core no matter if it looks like it is closing or not.

[basketcase0302]

What the piping should look like, (if it had 358 miles on it)!

[tuned88]

Thanks for the helpful replies everyone. The engine compartment photo confirms I'm plumbed correctly. This weekend I'm going to drain the radiator (in mah truck) and change out hoses and that valve. It would be so cool if that's the source of not being cool in my cool truck....sorry.

[tuned88]

I ordered the heater control valve from LMC. Just dropped it in and am happy to say success has been achieved. The fact that it was 103 today notwithstanding, I could clearly tell the difference between hot heater air and ambient air. The old valve appeared to operate normally but it must have been leaking internally. Thanks to everyone for the helpful input.

[Kurt Combs]

Please post about how adjustable it is, when it isn't 103 degrees outside. I changed mine a couple of years ago and it is either completely on, or completely off. I can get a setting in between full on and off, but it is really difficult to adjust it to that point. My valve is a plastic version, probably from O'Rielley's. So if your is easy to adjust, I will order one from LMC.

[tuned88]

I'll take it for a spin tomorrow morning before it heats up and report the results. The valve housing is metal. I assume the rotating valve inside is also metal but I didn't check.

[tuned88]

I'm very pleased with the heater performance. For starters, I warmed the truck up driving around the neighborhood. With the fan running and heater selected it's blowing cool air. I then gradually moved the slider control towards more heat and the temperature came up gradually all the way to max (which is where it always used to be with the old valve). I then moved it down in steps towards no heat and it came back down in the manner expected. I never seemed to get the cool air I felt when I first started the engine but that may be because the ambient air was a bit warmer. All in all, success.

[hedz]

hmmmmmmm i think i have this problem too... thanks.