Blower motor resistor redesign?

[sargentrs]

While rebuilding my factory integral AC unit, I decided I need to replace my blower motor resistor. Apparently, the AC part is not remanufactured by anybody while the heater only resistor is readily available. Somehow mine had apparently contacted the blower wheel which caught it, bent it into the housing and melted the casing. I know I can probably just substitute a heater only resistor on one from a Mustang or other Ford car but this got me to thinking about a more modern redesign. 68RGR (thanks, Bill!) had a suggestion he posted here in my thread, about 2/3 down the page http://www.fordification.com/forum/view ... 3&start=15 Before a redesign can be attempted, some data needs to be accumulated. Unfortunately, I am "electrically deficient" and have no clue how to determine what specs are required. An ohm test across the terminals of the AC resistor yields readings of .9 and 1.7 ohms. I can assemble the needed components and solder them, etc but I'm not sure what to do. Anybody given this any thought. How about resistor wire similar to the ignition's pink resistor wire? It would be relatively simple to rig up a couple of different resistances to a generic plug from the fan switch. Thoughts, opinions?

[70shortwide]

Can you straighten out the coils? They don't look broken, and you said you were able to measure the resistance. I'd bend them back where they need to be and patch the housing.

[sargentrs]

Thanks, Jeff! Always an option. The terminal strips look burnt so I'll probably replace with a heater only resistor if I don't figure something else out. Putting all new switches and such on it anyway. Don't want to put it all back together, install it, and then something crap out afterward.

[sargentrs]

Just throwing stuff out there. Instead of reinventing the wheel, what about the newer model designs? I realize this is for a 4 fan speed application but would only require a narrow slot to be cut in the housing. Easily modify the harness to use only 3 of the 4 speeds. See anything wrong with it? http://www.summitracing.com/parts/smp-ru440/overview/

[mimku1971]

I've been following your factory AC "Suitcase" rebuild. My 71 has the same unit. If I read your original post correctly, are there two resistors for the fan? One for the heater and a second for the AC? I think theres only one on mine. Thanks, Mimku

[sargentrs]

No, there is only component containing 2 resistor coil wires. It's typically called the "heater" blower motor resistor because fewer trucks had AC and only came with a heater. In truth, it's just for the blower motor regardless of heat/AC options. Since it gets so hot and is so flimsy, it's mounted inside the case on both the heater or AC units for overall safety/protection. The way it works is that on low speed, the current runs through both resistor coils in series, on medium speed the current runs through only 1 resistor coil and on high speed the resistor is bypassed totally allowing a full 12v to the blower motor. On low and medium speed the current is reduced via the resistor to limit the speed of the motor.