heater/defrost fan motor not working

[Steve83]

I just mounted the new one in a place that was accessible and pulled the old wires off and hooked them to the new resistor.

The resistor is 1) bare wire, & 2) mounted inside the airstream because it puts off a LOT of heat, and it NEEDS to be forcibly air-cooled.

Works fine.

I hope you carry a fire extinguisher.

So, I pulled the fan and spun it and turned it off and on. But still no sign of life. ... Should I get some long wires to go straight from battery to the on and off switch or to the back of the fuse box?

Neither. Jumper from the battery terminals directly to the motor terminals. Get a firm grip on the motor before you make the final connection because, if it works, it makes a LOT of torque, and will jump as it starts.

How would you guys proceed with the process of elimination?

I'd proceed with the process of DIAGNOSIS - not elimination.

 

[work765]

Still the fan motor itself. It's still the easiest to test at this point, since it's out.

Run the jumper wire, or just put the fan motor up at the battery to save you the hassle, and see if directly connecting it to the battery does the trick. If not, then it's your motor.



If it does (and watch that it doesn't spin out of your hand), then yes, you can run a jumper wire to the switch.

But here again, it's easier to use a volt-meter (which every Bronco owner should have) or a test light to see where the power ends.



Oh, and do you check the fuse first each time, to make sure it's not blown again?



Paul

So I finally got some free time and tested the motor. I ran 12 volts Straight from the battery and the fan motor came to life.
So I'm guessing it's a connection somewhere.
Couple questions.

The fuse for the heater fan is the fuse on the top top of all the Fuses?

*None of my fuses are blown in the glove box*

The Orange wire that is my hot to the fan motor goes behind the whole heater box and then disappears. Does it change colors?

The wires coming off the back of the heater switch are three. None of them are orange.

What do I do?


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[DaveLev]

I read this thread quickly: Have you checked voltage at the blower motor? Have you checked ground at the blower motor? Check voltage at off, high, and low.

It could be switch, resistor, or motor. The resistor lowers voltage from 12v to maybe 7v I don't remember for low speed. You can remove the blower, take those two wires off it, and run it to your battery directly to rule out the blower motor and to avoid buying a new one. Or buy 5 dollars worth of wire and a 10 amp inline fuse and run wires straight to your battery and to your fan and see if it runs.

Sorry if this has all been mentioned, but honestly the hardest part about the heater system in the bronco for me was getting that darn fiberglass part back into the dash with all the floor shifter and tunnel cover crap going everywhere. Plus those nice metal cables to open/move the vents and those terrible clips. Was not fun, but wasn't 'hard' per se.

Oh, and +1 on upgrading to a new core. I went with an aluminum one and also bought all new silicone hoses and a heater control valve for about 100. That stuff all works great now...better than new.

 

[DirtDonk]

The fuse for the heater fan is the fuse on the top top of all the Fuses?

Should be marked, but here's a pic. Just look at the orientation rather than the words if yours are hard to read.

The Orange wire that is my hot to the fan motor goes behind the whole heater box and then disappears. Does it change colors?

Nope. Well, sorta, but there is still Orange.
Is this a factory harness, or aftermarket? I forget if we've already talked about that.

The wires coming off the back of the heater switch are three. None of them are orange.

Then either they've been changed or are faded/burned? So what colors are they?
The factory colors are:
1. Brown - power in from the fuse panel.
2. Red - Low speed fan from the switch to the input side of the resistor
3. Orange - High speed fan directly from the switch to the output side of the resistor, where it meets the Orange wire to the fan.

What do I do?

Find out where the voltage stops is what. More work to do.
You've verified that the fuse is good, but what about the connectors? I would pull each fuse out and clean the contacts and put the fuses back in. Then verify with your volt-meter (you do have a volt meter now, correct? ) that the same power is going in one side of the fuse that is coming out the other side with the key in RUN or ACC

Get up under the dash with your meter probes and make sure the Brown wire in the center of the switch has the same voltage as the fuse when the key is on.
Then verify that the Orange wire (or whatever color your HIGH speed wire is) has power when the key is on and the switch is in the first position.
Then check that in the second position the Red wire has the same voltage.

But before all that, you should be checking that your Orange wire has battery voltage when the key is in RUN and the switch is in the HIGH position.
Stock, the switch would be wired in OFF-HIGH-LOW order.

Paul

 

[DirtDonk]

And just as a little side note.... That fuse panel pictured above used to look pretty nasty. Fuses rusted into place so i could not remove them, plastic itself pretty grungy and the contacts looking like they were on their last legs. I wish I had a "before" pic.

An overnight soak in EvapoRust and it came out looking like this.
Well, it looked even better at the time, but I let it sit untended for six months and didn't treat the metal or protect it in any way. And it also spent some time outdoors since then, so there's a tiny bit of the old reddish-brown showing back up.

Just a heads-up for when you're trying to salvage some old rusty parts. Especially the hard to clean ones like the contacts in a fuse panel.

Paul

 

[work765]

Should be marked, but here's a pic. Just look at the orientation rather than the words if yours are hard to read.

View attachment 407964







Nope. Well, sorta, but there is still Orange.

Is this a factory harness, or aftermarket? I forget if we've already talked about that.







Then either they've been changed or are faded/burned? So what colors are they?

The factory colors are:

1. Brown - power in from the fuse panel.

2. Red - Low speed fan from the switch to the input side of the resistor

3. Orange - High speed fan directly from the switch to the output side of the resistor, where it meets the Orange wire to the fan.







Find out where the voltage stops is what. More work to do.

You've verified that the fuse is good, but what about the connectors? I would pull each fuse out and clean the contacts and put the fuses back in. Then verify with your volt-meter (you do have a volt meter now, correct? ) that the same power is going in one side of the fuse that is coming out the other side with the key in RUN or ACC



Get up under the dash with your meter probes and make sure the Brown wire in the center of the switch has the same voltage as the fuse when the key is on.

Then verify that the Orange wire (or whatever color your HIGH speed wire is) has power when the key is on and the switch is in the first position.

Then check that in the second position the Red wire has the same voltage.



But before all that, you should be checking that your Orange wire has battery voltage when the key is in RUN and the switch is in the HIGH position.

Stock, the switch would be wired in OFF-HIGH-LOW order.



Paul

This whole time I thought the heater fuse was on the top! Finally got some time to look at it and compare to your image Paul. I pulled out the old fuse which looks okay and swapped with a new one and presto!! Heat was blasting. )

Gonna be perfect for our 45min trip to the big car sweep meet tmrw AM with my son!!

This whole time I was focusing on the wrong fuse. What a waste of time! Sorry guys

Thanks Paul!


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[DirtDonk]

Haha! Success!
I'm kind of prone to wasting my own time, so whenever there was an electrical issue I would just check all the fuses. Since there are only the five on an Early Bronco, that didn't really take too much extra time to pull and check all five.
In the old days I was never really sure what other circuits might be under one fuse but not listed on the front of the panel. Figured there might be a sneaker wire in there somewhere I didn't know about, so I'd just pop 'em all out!

Might not be a bad idea to do once in awhile anyway, to keep the contacts clean.

Glad you've got heat. And just in time!
Did you use a 20a fuse like shown on the panel markings?

Paul