Ok, here is the situation. My blower motor hasn't been responding to my fan switch for a while now. So Saturday I switched out the blower motor. No dice...

So then I pull the switch and replace it too... Still nothing...

Fuses are fine, so what could it be?!?

 

I'll bet you lunch that the blower motor's resistors are shot.

Check the connector, first. The speed resistors are located on the heater/evaporator box, to the driver's side of the fan motor. Look for a funny looking gray connector, 4 wires going to it. Pull off the connector; the resistors are hanging upside down, held down by two 9/32" bolts.

There might be corrosion inside the connector as it goes to the speed resistors. Try wiggling the connector, with your engine off, selector set to "heat", and fan speed to "3/4 speed". See if anything happens. Sometimes tapping above the resistors gets 'em to kick in.

If not, try to get the resistors from a junkyard. Both times I got them (myself and for a friend), they let me have them for free.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Would it be possible to test the resistor by connecting the A slot to the D slot with some wire?

 

I'll bet against the other post that the problem is the battery feed to the control head. The resistors almost never fail; and even when they do, it's impossible for them by themselves to kill all 4 speeds, because the high speed doesn't use them.

Pull the head out of the dash, enough to get a hand in behind there; follow the brown wire back away from the head, and in about 12" or so it will plug into the brown wire that feeds the whole system its power; there's a connector of extremely stupid design there, which always burns up. That's your problem. Replace it with a high-current type of slide or bullet of some sort.

BTW there is one of the same idiotic connectors in the big red wire that carries battery for the high-speed mode to the relay. Follow the red wire from the relay over the evap housing toward the left, just about right above the pass side valve cover there's a connector block with the red wire, 2 green ones, and a black one; it's usually wasted too.

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"So many Mustangs, so little time..."