Blower motor works on high only

[Detector]

Now I've run into this problem before but darned if I can remember what causes it. The heater blower motor works on high but nothing on the lower speeds.

Also, I noticed I had 2 fuses missing from my fuse box under the dash one was the heater(14A) and the other was courtesy lamps(14A). I put new fuses in thinking that was why my heater blower didn't work, even on high, and then it would work on high but nothing lower. When I checked a bit later I saw both fuses were blown. I've got a pesky parasite drain somewhere as my battery will be dead if I leave the battery cables connected all night. I can also see sparks when I connect the battery cable when nothing is turned on or no doors open. I must have a short somewhere.

I did the test with my multimeter with everything off I get a 12.4 v between the negative battery terminal and the cable. I've traced it as far as the big yellow wire running from the right side(+) of the starter relay on the fender to the ignition switch that is drawing voltage even when the switch is off.

 

[TheJ]

Well if this was a newer car I would say your blower motor resistor is bad and needs to be replaced. But I don't know if our cars have one or if it is internal to the switch. Someone else might know.

Edit: After looking through my wiring diagram there is a blower motor resistor. As for the parasitic draw check the resistance of the suspected wire and continuity. Like you said it could be a short to ground.

 

[c9zx]

+1 on the blower resistor, it is on the blower case. Unplug the clock, if it has one, and see if the drain stops. They usually burn the coil open when they stick but it is a possibility. If that is not it pull one fuse at a time until the current flow stops. That will at least narrow it down to a lesser number of circuits. Then put that fuse back in and start disconnecting one thing in that circuit at a time until current flow stops again. That should put you very close to the problem. Chuck

 

[machman_73]

http://www.7173mustangs.com/thread-heater-box-resistors?highlight=heater+blower

 

[JohnsonEdwin]

What is main reason of this most of use this blower motor?How can apply this Blower motor for car motors?

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