Hey hey FTE. My heater randomly shuts off in my '73 F350 390....any ideas why? It runs for about 5 min then shuts off. So I'll turn it off, then when I turn it on again it works for another 5 min. Not sure what's going on.....

 

Fan or heat from the core?

Fan, could be the relay right under the glove box.

Heater core, could be a air bubble in the cooling system OR it could be the vacuum operated heater valve. Need to check the vacuum lines, especially the ones around or near the vacuum accumulator.

 

Yeah, it's the fan. It just stops.

 

There's no relay in this setup, just the speed switch, blower resistor, and motor. I'd check for power at the blower motor during the failure condition. If you have power at the motor when the fan should be ON yet the blower motor is not actually running, then this would indicate the blower motor should be replaced.

 

maybe a new motor with a thermalcople? I know a/c motor have this but d/c.have to check on that

 

What do you guys recommend for a repair manual?

 

I recommend us....

and a close 2nd the factory service manual available in print and CD on eBay and elsewhere...


I would say your switch is overheating.

Josh

 

I've learned everything I know so far from this forum. As a first time owner and hobbyist repair man, you guys have made me.

I'll take a look this weekend. Thanks!

 

I would say bullitt is right ,the switch contacts heat up and open because the bi-metal got weak,replace switch and/or find out why the switch is getting over worked like loose conntions or dirty contacts old blower ect.