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Discussion Starter #1
Hello,

I currently hit a major roadblock on my restoration. I recently replaced the heater blower motor, box, and resistor. For some reason, my blower motor won’t shut off. As soon as I connect the brown wire from the harness to the brown wire on the blower motor, it runs full speed and won’t shut off. I tried unplugging the yellow wire on the resistor and the three plug wire on the resistor and it still runs with those unplugged. Any help is appreciated, I’m at my witts end with it.

Thank you!
 

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it sounds like you have a hot lead going directly to the blower rather than to the switch (or at least through the switch first). Is it factory wiring, or a replacement wiring harness? If you have an early 65 switch, off is in the center btw...
 

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Discussion Starter #3
It’s a 1966 Coupe. The heater version is the 2nd series, two wire yellow/black. I initially made the mistake of purchasing a 1965 blower motor that was three wire. That’s gone now and it has the correct 1966 two wire motor. It has the original wiring. I have a black/green wire going from the hot ignition post to the fuse block. A brown wire out of the fuse block to the heater motor. Wired just like this http://averagejoerestoration.com/re...stang-wiring-and-vacuum-diagrams/67heater.jpg. i have a good 12v going into the fan motor From the brown wire and 3v coming out of the fan motor into the yellow wire.

i appreciate your help!
 

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66acces1.jpg
20200302_105257.jpg
 

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Discussion Starter #6
Thanks for the diagrams. I have the system wired exactly like it says. If nothing down system (resistor, heater switch) is hooked up should the fan run? As soon as I plug the brown wires together it turns on full bore. What in the system kills power to the motor?
 

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The 66 heater motor is supplied 12v when the key is on and speed is controlled by resistance to ground. If it runs with the 913(yellow) wire disconnected at the resistor but not at the bullet connector at the motor, you have a grounded 913 wire. Maybe it is pinched somewhere.
 

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Discussion Starter #8
I will start there. So somewhere between the heater motor and the resistor plug the yellow wire is grounded. Also, when I checked the voltage this morning there was 12v going in through the brown and only 3v coming out into the yellow. Shouldn’t they both be 12v? You have no idea how thankful I am for the help. This issue was driving me nuts.
 

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Discussion Starter #10
Whew okay. I read on another forum you would. I will run the yellow wire out this afternoon and let you guys know how I make out. Thanks!
 

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Discussion Starter #11
Okay. Leaving the brown wire bullet connected together, I took a test wire and ran it from the yellow bullet plug of the heater motor in the engine bay directly to the bottom right prong on the resistor. (The three wire switch plug was unhooked on the resistor). Still runs in the ON key position. Does the dash switch need to be in?
 

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With the plug off the resistor you shouldn't have a path to ground (that happens through the switch), so your motor shouldn't run. Make sure your jumper connection isn't touching a ground source. Also if you have a multimeter check your resistors to see if they have become grounded.
 

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Brown wire 181 plugging into the blower motor should NOT have power until key is on ,Are you sure the key is OFF to start with ?

connect the brown wire from the harness to the brown wire on the blower motor, it runs full speed and won’t shut off. I tried unplugging the yellow wire on the resistor and the three plug wire on the resistor and it still runs with those unplugged
So sounds like the motor is grounded somehow if it runs with ONLY the brown wire hooked up.
 
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