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Discussion Starter #1
Hi all, I have a two wire three speed heater blower motor that won't work properly. I have read some trouble shooting procedures from some previous threads with no luck. It runs independently connected to the battery. It also runs at high speed with the yellow wire grounded. I grounded the switch independently and it ran with the switch in the off position only, but with a voltage drop. 8 to 5 volts. I have a new switch and new resistor. Wondering what the next logical step might be moving forward. Thanks in advance for any help.
 

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This may not be any help, but I was having a lot of trouble with my 3 speed heater motor not working also. I tested the motor and it was working fine directly from the battery as you did, but would not work when wiring was connected through the harness. Traced my problem back to the fuse box. Fuse was good but I noticed when I jiggled the wires going to the fuse box, the heater motor would work intermittently. I had a loose wire going to the heater motor fuse terminal. Easy fix once I found it.
 

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The three speed heater motor has constant power with the key on and changes speeds by resistance to ground on the yellow wire. Pull the single yellow wire off the resistor and ground it, the motor should run full speed.
If it runs your problem is resistor, switch or wiring between switch and resistor. It ends up grounding through the switch so it must have a good path to ground.
If it doesn't run then you probably have a wiring problem back to the motor.
 

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Well, the wiring is a bit unorthodox. When the ignition/accessory is on, the blower is powered. The ground circuit goes to the dash switch. Off means it is not operating. Low goes to one side of the resistor, medium another, and high goes straight to ground. Of course, to operate the resistor must be connected to ground.
 

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Discussion Starter #6
Well it looks like I found the fix for the issue I was having with my heater. The new switch I bought from a reputable vendor wasn't grounded properly. Just a spec of solder between the ground strap and switch housing. Re-soldered the ground to housing and everything is working as should. Hope this helps others with the same issue. Be safe everyone.
 
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