'77 GMC Electrical Issues

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Mlcdc1

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Aug 19, 2016
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37
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Location
IN
First Name
Matt
Truck Year
1977
Truck Model
C10
Engine Size
350
Bebuilding my '77 GMC pickup and pulled the old wiring harness (painless wiring #10205) from the cab and installed it in the new cab. I didn't add any extras and used the components (steering wheel, switches, etc) from the old cab. When I tighten the wiring module to the fuse block under the hood, the parking lights and interior lights come on without the switch being on. Only the right front turn signal works irregardless of with direction I move the lever. If I unplug the switch harness from the switch, I have front blinkers and only the right rear blinks. I have installed a new light switch, floor dimmer, and traced the wires - found nothing. The wiring harness was working fine in the old cab before the transfer. I'm at a loss and would appreciate any suggestions that might help. Thanks
 

Rusty Nail

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Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Irregardless? Is not a word.

Sounds like a ground is switched with a power wire. I'd check the headlights.
 

Camar068

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1986
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K10/LM7 5.3/4L60e/np208/3.73/32"
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10 yrs Air Force

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