Hi Guys,

I need your expert knowledge on the wiring of the heater switch for the 67 F-100. This one is "Off-Hi-Lo" and the switch is a **** style, specifically not like the 68 thru 72. I will explain this as best as I can...

There are three connections on the back of the heater switch. One is marked "B" one is marked "H" and the other is marked "L". Now I assume the B is 12V power from the fuse box and the H and the L has something to do with the high speed and low speed of the heater motor. Coming off of the H and the L are a red wire and an orange wire. Where do these wires go?? Now there are two connections on the back of the heater plenum where I think they are supposed to go but I am unsure. I think this is some sort of internal resistor to make the hi speed go to low, but I am not sure. Please help. The way I have it wired now is blowing my fuse. I have the red wire connected to the lower connection on the back of the plenum and the orange wire connected to the top connection. NOTE: The orange wire also connects directly to the heater motor.

Yes I do have all of the wiring diagrams for this truck, but it does not include the schematic from the heater switch to the heater motor.

Thanks for any help.

 

B is 12v source(brown wire), H is the high setting(red wire), L is the low setting(orange wire).

The orange wire is the one that needs the resistor, it cuts down the voltage to slow the motor. Red is the full 12v for the high side. The way my schematic explains the wiring is there is only one wire going to the blower motor. The red and orange wires splice together after the resistor then the wire becomes a black/red stripe wire. You should take a look inside the box to see what you are trying to connect to. It could be the resistor or it could be something else. Then you will fully understand why you keep popping fuses.

 

Sounds like somone put a switch from a 50's truck in there.

Does it have a brown ****.

you can see a picture of it on page 2 of the electrical section of the NPD online catalogue

 

Thanks for the help. It was the Heater Motor Resistor that was shorting out. It was broken and touching the metal backing of the heater plenum. I guess a 40 year old resistor can do that. Now the big problem becomes finding an original replacement resistor to replace it with. NPD, LMC, Dennis Carpenter does not have them. They are readily available to the old Mustangs, but I don't think its a direct bolt in replacement.


Thanks again.

PS: I do have the correct switch with black ****.

 

so now you are looking for this?

 

That's it! Only mine has only two prongs. That one has three, possibly for three speeds instead of two. But, That's it!!

 

I am pretty sure you can still get those through Ford. Check out the parts department at you local dealer and definately take the part with you. I had to find one and that is where I got mine.

 

I just checked NPD.
They have limited stock of a resistor for 68-72.

I don't if 67 was different but this is what they listed in their online BRONCO catalog.

18591 RESISTOR ASSY., Heater Switch
F100-350 68-72 Limited NOS stock availability .................... F-18591-1 19.95
F100-350 73-86 Heater .................................................. ....... F-18591-2 12.60
BRONCO 78-79 Heater .................................................. ....... F-18591-2 12.60
BRONCO 80-86 Heater or aux heater ................................... F-18591-2 12.60

 

My local Ford dealer told me that he can't get them anymore. He did say if I could find the Ford part number he could research it a little, but I did not see a part number on it.

I also called NPD to order one but they said thay have stopped carrying them for my application. Now, it is possible that another year will work, I'll just have to do some research along with some trial & error.

 

Got it working. Ordered one from NPD for an early Mustang. With the help of a Dremmel tool I was able to make what I needed. The Mustang resistor was for 3-speeds so I ended up removing half of the resistor and it worked fine for my 2-speed application. Thanks for all of your input.

 

I have a 72 F 100 1st 1 I've had about 20 years Ford that is. when I got the truck the heater motor was laying in the floor 1 of the wires was broken so I had to open up the motor and solder. the problem that I am having now is that I do not know where to reconnect the black and the red wire?

 

I posted a question about where to run the wires and hadn't gotten a reply,did I post it incorrectly?