Electrical help with heater blower on '78 SA FJ (1 Viewer)

Cromagnon

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Jun 8, 2012
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Colorado Springs, CO
 
It appears you have a wiring problem. Somehow you are getting 12V on the WB wire. As I said earlier that needs to be ground. It looks like if you correct that then the circuit will behave as expected. Do you have WB wired to the heater switch? That would be the first place I would look. Pictures of the connectors and the wire colors would be helpful at this point.
 

Cromagnon

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Colorado Springs, CO
 
When I plug the blower back into the circuit that is when it will run with the engine OFF but as I turn the key to ON I lose power.
You aren't losing power, there isn't any difference of potential between the switched leads and the 12V on the ground. If the blower motor were grounded to the chassis you would be blowing fuses or have melted wires and a fire.
 
Joined
Jul 15, 2020
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Lakefork, Idaho
Here is a photo of the fan pull switch and the plug I found under the dash. I can't really get any better view of it or the wire color.

20201107_155227.jpg


20201107_155105.jpg
 
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Messages
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Lakefork, Idaho
I thought maybe I had installed it backward but there is only one way to attached the switch to the under dash plug.
 

Cromagnon

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Messages
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Location
Colorado Springs, CO
 
The female receptacle in your hand has what color wires going to it?

The switch has four wires, LR, LB, LW and ??, going to a male plug. The wiring diagram that I have shows three wires going to the heater switch, LR, LB and LW. If the there is a second LB wire, it would go to the rear heater.

The wiring diagram also shows the WB wire at the blower motor goes directly to ground. That needs to be confirmed as well.

With everything disconnected, the motor off and the key in the ACC position, do you see voltage on the LR wire at the receptacle in your hand?

With everything disconnected, the motor off and the key in the ON position, do you see voltage on the LR wire at the receptacle in your hand?
 

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