When light switch is turned on just the turn signals work

1990 GMC TRUCK
232,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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COLLIN LACOBELLI
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My brake lights, reverse lights and turn signals work fine with light switch turned off, but when turned on just my turn signals work. Also my parking lights don’t work at all. I have brand new taillight circuit boards and bulbs installed, I also went through the harness at the back of the truck and replaced the ground as well, can’t seem to figure it out.
Feb 11, 2020 at 6:06 PM
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PORTAFISHING
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  • 37 POSTS
Hello,

Sounds like maybe a multi-function switch issue. Is your headlight switch and blinkers all together?
Feb 12, 2020 at 8:44 AM
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COLLIN LACOBELLI
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The headlight and running light switch is on the dash and the turn signal switch is separate mounted on the steering column.
Feb 12, 2020 at 8:57 AM
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PORTAFISHING
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Okay, does the same thing happen on bright and dim?
Feb 12, 2020 at 9:20 AM
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COLLIN LACOBELLI
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Yes it does.
Feb 12, 2020 at 10:54 AM
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COLLIN LACOBELLI
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I was messing around with it tonight and noticed that the parking, brake and reverse lights are on but are so dim it’s unnoticeable.
Feb 12, 2020 at 6:30 PM
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PORTAFISHING
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Sound like a bad connection, maybe a ground. I'll see if I can find you some wiring diagrams to help.
Feb 12, 2020 at 8:10 PM