Help Needed: Diagnose No Running/Tail/Courtesy Lights
Hello Fellow Forum Peeps!
I'm having a bit of a conundrum regarding lights.
I've got a 3300 GV SBI on a Chevy P30 7.4L 454 - 1987
Currently, I'm not getting the tail lights (back end red lights that should be on when headlights are on) or courtesy lights (lights around the top of the coach when headlights are on).
Headlights (high/low), brake lights, reverse lights, and signal lights all work fine.
They did work in the past. But, when they worked my headlights didn't. My old headlight switch had a short in it that was causing it to pop the headlight breaker. With that old switch, all of the lights worked... though just for a short period of time before the fuse blew and the headlights would go out.
I bought a new switch and installed it. The short is gone. The headlights run great (though they are super dim... new project... switch to high-powered LEDs or something 
). The brake lights run great. The signal lights run great.... no dice on the running/tail lights and courtesy lights.
Things I've tested so far:
-On the switch: the power line for the running lights (number 5 on the attached switch diagram - IMG_2050.gif | Orange wire on top right of IMG_0253.JPG). It's got 12 volts.
-On the switch: the switched running lights wire (number 4 on diagram. Orange wire that's turned a bit brown with the blue connector in IMG_0253). It gets power when in the Parking Light Position and the Headlights position like it's supposed to.
-On previous two points, got info on switch from here: GM Headlight Switch Circuit Functions | American Autowire
-On the fuse block: tested the fuse for tail/running lights. It's good.
-On the tail light contraption itself: The bulbs... they are all good on both sides.
-On the tail light contraption itself - pic attached IMG_0251: The brown wire gets 12v in the "Headlights On" switch position. None of the other wires get 12 volts in any headlight switch positions.
IMG_0254 - The headlight switch itself. It has 3 Positions.
1 - All the way in. Everything off.
2 - Half way out. Dash lights come on.
3 - All the way out. Dash lights say on. Headlights come on. Floor switch allows toggle between high/low beams
In all three positions the switch can be turned left and right. All the way left has a "notched" position that I believe is a "full on". As you rotate it to the right, it will dim things depending on switch position.
In positions 1, 2, & 3 - The "notched" position allows map lights in overhead dash to be used. If you rotate to any dimmed positions, the map lights go out.
In position 2 & 3 - The notched position has dash lights at full brightness. They dim as you rotate to the right. All the way to the right cuts off the dash lights.
In Position 2 - None of my headlight indicators turn on. (I think from the old switch that the "Parking Lights" indicator should come on). Indicator lights noted on IMG_0255.
In Position 3 - My "low beam" headlight indicator turns on. Clicking the floor switch turns off the "Low Beam" indicator and Illuminates the "Hight Beam" indicator.
At this point, I've exhausted my knowledge. I don't know what else to test. By all accounts... the lights should come on. 
Thanks for any help!
Topic: Help Needed: Diagnose No Running/Tail/Courtesy Lights (Read 713 times)
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