My new to me '76 F250 SC 460 C6 w/factory AC had no fan switch when I got it. I installed a new one and the fan seems to work correctly. Last night I noticed a three prong connector dangling up behind the back of the glove box. Supposed to be a resistor plugged in here right? I have no blower resistor plugged in but the fan is working at all the speeds. Should I be worried about this? Could the switch have the resistors built in? I don't want to burn up any wiring or switches. Should there also be a fan relay someplace isolationg the switch contacts? If so where? It doesn't appear on any diagrams I've looked at.
Thanks

 

The blower resistor is mounted in the heater plenum to help dissipate the heat. The only part visible is the three prong plug on the side of the plenum behind the glove box, which the connector plugs into. With the resistor disconnected, the fan should run on high speed only unless someone has jumpered the wires together on the switch.
What kind of tractor do you have, tractorman? Brian

 

My tractor is a 1948 Ford 8N.
My heater fan on the truck seems to work on all speeds and they are different, and the wiring harness is just dangling there not plugged in. I just don't want to smoke anything in the harness or connectors. This is not the first electrical mystery I have found by the PO that did not seem to know what the hell they were doing. Does the power originate at the switch to the resistor and then the fan. Mine is powered at the switch with a big orange wire.

 

To the best of my knowledge, the power originates at the switch then goes to the motor. You might check the switch over for resistance between the output terminals to see if there is some kind of an internal resistor, but a resistor big enough to dissipate the power required would be pretty big, that's why the OEM one is mounted in the fan box to keep it from getting too hot. How many terminals are on the replacement switch? There should be continuity between the switch terminals for intermediate speeds and the resistor connector that is dangling behind the glove box.

I have three Farmalls: a '40 A, a '37 F-20 and a '47 MD. Brian

 

Mike, I have the same problem with my 390 1976 4x4 w/ac. My Blower motor relay has been removed. That is what it is called on the wiring diagram. It is also called a Accessory Safety Relay. Mine has been straight wired across two of the ends of the 3 prong plug that is just hanging there. The wiring diagram shows the orange wire goes to the starter relay, the red w/black stripes goes to the fan control, and the yellow w/2 red stripes goes to the ac mode switch. If I remove the strapped wire that is across the red w/black stripes and the yellow w/2 red stripes, my fan will not work.
With the strapped wire removed and measure the voltage across all three wires coming into the plug, the orange wire is hot all the time and the red wire is hot when the fan switch is on. I have posted questions about this before and didn't get any info that really answered the questions. I asked some local guys about this and they said along as it works don't worry about it. I am just wondering if the fan is getting all its power with the relay missing. A guy at napa said if I bring the diagram in he could tell me what kind of relay I need. I have not had time yet to take the wiring diagram into him. I don't know if this helps you or not. But when I find the Relay number I will let you know.

 

Does this look familiar?

http://www.clubfte.com/users/mil1ion/ACplug.JPG