Improving the heater?? Freezing over here!!
 

Hey folks, I wonder how hot your heater blows. Mine is luke warm. I checked the mix door (externally) filled the radiator to the top and I get good airflow out of the heater vents, but it's just not as hot as I would expect it to be when the engine is at temp. It has a 195 thermostat in is.

Hoses are routed from the intake to the carb plate. From the carb plate to the heater core and from the heater core back to the top of the water pump. Is that correct?

The only think I can think of is that the heater core is somehow plugged up and not allowing heat transfer or the hose routing is wrong. The mix door would seem obvious, externally at least, it appears to close all the way and is adjusted well.

BTW, this is a 1975 F250 4wd with no AC and it does not have the cable/vacuum controlled valve in the heater core hose. Coolant should slow to the heater core all the time.

Also, the fan blower screetches like a skinned cat when you first turn it on, but then it stops and there is good air output, the air is just not as hot as it should be, or I think it should be anyhow.

1973/79 F100/350 & 1978/79 Bronco with factory installed integral A/C have a vacuum controlled heater water valve (D4AZ-18495-A). No factory A/C, no heater water valve.

The cable operated heater water valve (C3UZ-18495-A) was found on 1963/67 E100's and 1965/66 F100/1100's with the deluxe fresh air heater, all 1967/72 F100/750's with/without A/C

The heater works very well in 1973/79's, yours must have a plugged up heater core, because after about 5 minutes, you have to turn down the fan, open a window a bit.

so have you confirmed your coolant temp with an actual thermometer? sounds like the classic stuck open thermostat...

Yeah my '77 non A/C had the same problem. All I did was remove the two heat hoses at the motor ends and blow compressed air through each a few times. Not full 120psi just low pressure maybe 20psi or so. Eyeball melting heat since then

Feel your heater hoses when warm. If the outgoing hose is colder than the in hose the core is plugged. Try reverse flushing it with a garden hose until the water comes out clean. These trucks normally put out really good heat

I had a similar problem, I ended up replacing my heater core. When I did, I found that it was not only plugged up pretty well internally but it was also well covered in 40+ years of dirt, cobwebs, etc. Also it was loose in the box. The heater core is installed into the ducting with a foam tape around it so that it seals into the ducting forcing air to only go through it. When that foam breaks down it allows air to just go around the core not picking up heat, which diminishes the output. Popping the core out is pretty easy on a non-A/C truck, I'd say why not replace it.

If it warms up slow, that could be due to a missing thermostat. Do you have water flow through the radiator right after a cold start? There should be none or very little. The upper hose should stay pretty cold, then all of a sudden, it'll warm up as the thermostat opens.

Michael

Good thought to check your ducting and cowl vents for debris.
How is the air flow though? If you get a lot of blowing, but not much heat, then it's likely a coolant issue or a damper door somewhere. But if you get good air flow out the vents and it's just not hot, sounds like a coolant issue in the core.

I've seen plenty of these trucks (and others) where the fan motor makes a lot of noise but does not blow much. And still others where the fan just no longer has the freedom to spin well. Both cases can come down to just an old tire blower motor, but lack of air flow can be damper door malfunctions too.

Good luck. Sucks to be cold!

Paul