Heater Blower Fan

[67MercM100]

I've got a couple of questions regarding the heater blower fan.

First: My 20 amp heater fuse keeps blowing. It may even be blowing without the heater fan being plugged in. I'm going to have to check on that (if I can find some more fuses). I don't think the blower fan wire or the two resistor wires were plugged in when I got the truck. I might have plugged-in the obvious wire to the blower motor. I only just recently learned about the resistor.

Would not having the resistor plugged-in have an effect on the blower motor working and/or the fuse blowing? For what it's worth, I understand that the power for the blower motor goes through the wiper switch - and the wipers work.

Second: Can you test a heater blower motor with 12 volts right from the battery? I'm not just not exactly sure how the resistor factors into all of this. But the motor did absolutely nothing. Is there a better way to test the motor? Would a non-functional motor cause the fuse to blow?

As always: Thanks in advance.

[fordman]

what the resistor does is to lower the voltage going into the fan when the fan switch is move dto a certain point. if the switch is on high the resistor wont do anything except let the fan run full speed. with full power. so yes you can test the motor with a full 12 volts. and i think that hwne high is selected that the power actually may bypass the resistor switch and go directly to the fan. i am not sure on that and would have to check to be sure. i think i will have to consider what it might take to blow a fuse with the blower motor.

EDIT: I t does kind of bypass the resistor. according to this diagram. http://www.fordification.com/tech/wirin ... heater.jpg

as to whats wrong though. i may actually suspect the wiper motor going bad. but it could be the internal windings of the blower motor. it could also be a wire rubbed raw and going to ground.

if i was all alone in the world and had to test this out myself. i would disconnect the blower motor. either at the switch or just disconnect the motor by itself. then i would turn on the wipers and see if the fuse blew. if the fuse stayed working then that narrows it down to tthe blower, switch, wiring or the resistor. after that i would unplug the motor and leave everything else plugged in. the switch and the resistor wiring. turn on th eswitch and see if it blew the fuse or not. if everything was good it would tell yo uthe blower motor is bad. if it blew in any of the tests then it is before what is still plugged in.

[67MercM100]

Fordman: you think the wiper motor might have something to do with it? I guess I'm not understanding that. Or did you mean that the blower motor might be bad? The fuse blows w/o the wipers on. Interestingly enough, the wipers work w/o the 20 amp heater fuse even IN the fuse bock.

You had some blower motors for sale didn't you? Maybe I should just try a different one and see what happens. Could you PM me with a price?

[fordman]

oops the heater is its own fuse. it has nothing to do with the wipers. i read that you said wipers and i seemed to remember soemthing about wiper power being shared with something. but it isnt the blower motor. i got mixe dup. also in the way you described the problem it reminded me of a wiper motor problem i seen once. and it was in the cortrols of the wiper motor that were wierd. i think.

i would test your motor before buying one though. pm me zip code for a shipping quote. if you want one of them.

[67MercM100]

Well, Fordman, don't worry about the PM that I sent you about a heater blower motor. I was able to do a better test on mine and it works.

I'm still stumped about the 20 amp heater fuse continually blowing, though. The fuse will immediately blow with my test light on it when I turn on the ignition switch.

I disconnected the wires at the fan switch and it still blows the fuse. That would tend to rule out the fan switch.

I disconnected what I believe is the wire coming from the hot wire to the fan at the wiper switch. On the back of the wiper switch it looks like there is one plug with a group of wires that are solely for the wiper motor itself. Then there are two more that - based on http://www.fordification.com/tech/wirin ... wipers.jpg - appear to operate the washer pump. Based on the schematic, the black w/ white stripe wire goes out to the pump. I unplugged the other one. The part that I don't understand is that there were a couple of orange wires along with the black one that all came together in the one connector at the wiper switch. (those orange wires might have had a stripe or might not. Previous owner sprayed inside the cab; so ALL of my wires appear to be mostly lunar green.) Whatever I disconnected, the fuse still blew. But now I can't remember exactly what I did to make it blow. I might have run the wipers or I might have used the test light at the fuse. If I did in fact disconnect the hot wire coming from the fan wire, then it doesn't appear to be anything with the wiper switch - does it?

It doesn't appear to ever blow with just the ignition on and no load put on the fuse. Then again, it might just take it a while. But if it blows immediately with the test light - is current even flowing toward the heater fan switch?? What does that mean? A ground in the wire between the fuse and the heater switch? It all disappears into the big wrapped "loom". So there's no way really to trace it.

Maybe I'll just take it to someone and have that circuit rewired...

[fordman]

too late i already sent it.

[67MercM100]

too late i already sent it.

You did?? Do you even have my address?? Guess I'll have a spare.

[Thunderfoot]

I'm guessing from your user name that your truck is a 1967...? it makes a big difference in the wiring in comparison to the 68-72's...
From the diagrams it does show that the power wire for the heater also supplies the power for the windshield washer, but the wire diagrams for the 67 models is/can be sketchy, as Ford made changes to the truck wiring mid year or so and some of the wiring is not on a schematic (that I have see)...

With what you describe you have a partial short somewhere and when you add the test light it takes it over the fuse rating, were as just letting it run for a bit will finally blow the fuse as well.
You need to unplug the power wire off the back of the fan switch on the dash (Brown wire) and see if it still blows the fuse, as the problem could be the switch. To tell if this same power is also going to the Washer Pump check the Black wire on the Wiper Switch for power without the Heater Fuse, if it has power then yours is not wired into the heater, if it doesn't then unplug it as well and see if the fuse still blows. If having all this unplugged still blows the fuse then either the wire is shorted to ground somewhere (wire rubbed through) or it has melted the insulation somewhere to another wire or ground, or there is a wire spliced into it that shouldn't be and it is shorted or drawing to much current.

[fordman]

too late i already sent it.

You did?? Do you even have my address?? Guess I'll have a spare.

i already sent the pm not the part. i dont have your address.

[67MercM100]

too late i already sent it.

You did?? Do you even have my address?? Guess I'll have a spare.

i already sent the pm not the part. i dont have your address.

OK. No problem.