I have a 55 F-100 I restored years ago. After I got it all together I only had the high speed for the heater. Never worried that much about it being in Los Angeles. The heater core just gave up a few day ago so thought I would get everything right this time. I'm not clear what I need. I think the speed is controlled by the switch. The switch has three prongs. I assume power high and low but the blower motor only has two wires. What am I missing here?

 

Many heater fan motors are slowed simply by a coil of resistance wire. Yours may be missing.

 

If your switch has three positions, one of those positions feed the heater motor through a resistor which slows the motor. Try the wire to the motor to the second "load" lug.
BTW, Firstrider on here is the go to guy for heater parts.

 

Ok lets say I move it to the second lug and I do get a slower speed. Now I don't have a high speed. Its like you get one or the other. The truck is at my place in AZ which I am moving to but I'm still living in CA and brought the parts back to get what I need to take back out. Now I am finding so far there are no reproduction heater cores which has totally surprised me. Looked at almost all the big vendors. NPD LMC etc.

 

As was mentioned in an earlier post, you should contact firstrider here on FTE. He has everything for heaters.

https://www.ford-trucks.com/forums/1...and-parts.html

 

The blower motor on my 55 has two wires. both were connected to the switch and the motor had a separate ground wire attached to it and it had both low speed and high.
This leads me to believe that both wires are speed wires because it will not run without the separate ground.

 

So you have three wires? I just have two. Maybe its the wrong motor or the motor is internally grounded and both the wires go to the switch

 

Wiring is not a strong subject here at the 1ST-RIDER house so will let that subject go to the elec. pros. I believe all above info should help you out .


As for the heater core here is what you need to do to make it like new .Remove old core , measure the width , length , & thickness . Search " Universal Carnegie Mfg." They are in Pa. On their web site you can view all the dimensions of the cores they make . You will find one to match . That is what I have been doing to make up the heater cores . Remove the tanks / headers from your old core w/ a map gas torch , clean them up with bead blast or sand blast , find a reputable radiator shop near you & explain to them what you need done . Soldering the tanks on is best left to the pros . A correct size replacement core will be around $100.00 but will last a life time . As you said while you are there at the disassembled stage of the heater build do it right .Good luck .

 

My blower fan has two wires, one black and one red. Because the heater assembly is mounted with rubber mounts there is a separate ground wire attached to one of the screws on the motor. Low speed is the black wire and high speed is the red.


If you are interested I have a complete heater box assembly, housing, fan and core that I have already sand blasted and primed that I would sell you. I boiled out and pressure tested the core as I was going to put it back in my truck but my sweet wife bought me a vintage air unit so the rehabbed unit is excess.


Gary


PS: I think there are some photos of it on my build thread.

 

your switch has three wires. one is the power in.
(this might be the middle connector).
of the other two wire connectors.
one is for full power, it goes direct to the blower.
the second wire goes to a resister then to the blower.
these two wires then connect to the same connector or wire, for the blower.
so the blower/fan should have two wires connecting to one wire, power in.
the second wire or connector for the blower is a ground.
now to confuse you, some vehicles send full power to the blower and use the resister and fan speed switch to change the fan speed prior to ground.
thats what is happening. when you see multiple resister coils with several wires going to it from the switch..
then the switch is grounded.
ps: most vehicles mount the resister coil(s) inside the fan ducting, to help keep the resister cool.

 

not being wise, but live here; one hot wire full blast on these, however my
three F350s will melt ya boots off. not complaining about heat on these
but wipers allways were bad from the get go (hoods door locks) oh well
we live with it....

 

Does your second wire run through a resistor and if so what kind of a resistor is it?