Driving SF to LA next month for Sevenstock. Trying to get my blower working so I don’t cook myself.

Blower has never worked since I bought car. Pulled the housing from the car and want to test motor. Input has two male tangs, both marked positive. Do I run positive 12v to both tangs at the same time, then run a wire from metal mounting plate of motor to negative as a ground? Am using my van battery as power source.

Have zero level wiring knowledge so forgive me if being dumb.

And…. If I have ti test or work on the fan switch, is there an easy way to get to the back of it? Would rather roast in the car than pull dash!

 

Was looking for the fault starting from
the blower motor and working backwards. Waiting on more expert knowledge before trying to test motor, next step was resistor inside blower housing. Just looked wrong, corroded and with one of the coils broken with a 1” piece of wire sticking out of it. Gave it a poke and it snapped off.

Picks below show broken coil and snapped piece lying at bottom of housing.

Am I right in the assumption that this resistor is dead? Common sense says yes… but best to check. And anyone got a par number!

 

Resistor is indeed broken, you are correct. Not sure if a replacement is still available though - check the parts diagram on foxed.ca for that.

As for testing the motor - one pin will get 12v, the other side is ground. The way the system works (on the the 83 at least, not sure what year yours is) is that 12v+ goes to the motor, ground comes out the other side to the resistor, which then has a series of wires (one per resistor coil basically) that goes back to the fan speed ****. The **** goes to ground - so whatever speed you've selected is grounded, completing the circuit through the appropriate resistor and voila - fan turns.

Again, this is based on my extensive rewiring on multiple 83's, I can check the diagram for earlier ones to see if its the same, but I bet it is. Pretty sure it was the same deal on my 85 as well

 

I've never actually replaced a blower on an FB, and the heater section of the electrical manual is lacking, but I would guess those markings denote the direction of the motor only (I assume one side will be negative).

Resistor is toast.

 

Just briefly looked at an 80 and 85 diagram, all setup the same as I described above.

For your quick motor test the polarity doesn't really matter, it might just spin backwards.

Also - you can bypass the resistor and just have it run full speed whenever on - better than nothing!

Edit: looked at the pic again and I see your confusion. I am assuming the little symbols mean that if positive is on that pin it spins the direction that arrow indicates or visa versa

 

Thank you mrtransam. Took your knowledge and tested the motor. Runs fine. I also found an always on 12v near the motor so at the very least can rig a simple switch and have an on/off blower which is better than none.

Also took a look for replacement resistor. No go. Found a thread adapting Mazda 323 resisters, but they also unobtainable. Gonna teach myself to solder and see if I can connect the gap i the broken resistor.

 

My guess on the positive is that which ever leg gets the positivem the arrow indicates the spin direction. One leg gets positive and the other gets negative based on the direction.

 

Alright. Did some messing around. Found if I bridge the resister with a screwdriver on the line shown as red…. I get a working fan that actually responds to the heater control off/low/med/high settings on the dash. Thinking of creating the screwdriver bridge using the two pin connector under the resister and calling this done.

Or will I set my car on fire?

 

Should be alright - that's essentially what the broken curly Q is doing anyway - bridging the two contacts.

Soldering is pretty easy, you could probably get that broken section stuck back together well enough for it to work

 

Sorry for posting so many times in a row, but I just thought of something - The non-AC cars had an additional resistor section (Pretty sure this is actually the broken part in yours) which would be activated to reduce the amount of air the blower would generate since it didn't have the added air resistance of the A/C evaporator/core.
You can easily bypass that and safely operate it - solder a wire where you have that red line and you should be good to go.

 

Could indeed be the case. My car left the factory with no AC. Anyhow… gonna bridge that gap then reinstall. And keep extinguisher close.

 

Shouldn't be dangerous.

Worst case the resistors are bypassed and the fan runs full bore. Just be mindful of shorts, but clearly that wasn't a concern with the original design.

 

Done! All back together and now I have a working blower, with three speeds to boot.

Appreciate all the helpful.

 

You can also buy new resistive wire and make your own replacement resistor to spec.

Also, here's a deep dive into some alternatives:

https://www.rx7club.com/1st-generati.../#post12429220

Edit: I'm also jealous, you are close enough to drive to Sevenstock and far enough to have an awesome drive!

 

I think I just hit lucky and hit by chance on a simple fix for none AC cars. Just bridged the two wires that go to the unused plug on the resistor and bingo….. Three speed fan!

I am am defn testing my range with driving to Sevenstock. I have done multiple 5 hr drives before with Breakfast Club, so have faith in the car’s reliability. Going to break it into two days. North end of Big Sur one day. South end the next. (It’s blocked by a slide half way down). Gonna be a huge help to have a blower! Working on getting some acoustic mat under the carpet by the time I leave too. And maybe a big subwoofer where the spare should be.

 

Looks like you fixed your problem, but similar resistor assemblies are available aftermarket. For example:

 

From poking around on RockAuto a bit, it looks like a few other 80's/90's ones could be adapted to work pretty easily as well. The one from a 626 and Miata look similar enough that I bet it wouldn't be too hard. I know the early Maita's use the same type of setup - the switch chooses which resistor the ground path goes through, like the FB

 

Maybe checkout blower motor resistor for an early model Mazda B2000 truck?