Flatbed Electrical Issues

LBZ_Duramax

Well-Known Member
Joined
Aug 18, 2011
Location
Benson, NC
I've got a new work truck/hauler. 2005 Silverado 3500 with the 8.1L. Previously an AT&T truck with a service body on it. I bought it after someone had swapped the service bed for a new flatbed. It had all sealed incondescent lights in the bed and I swapped those for clear lenses LED. Stock incandescent front lights. Everything has worked fine for over a year now. The other day I notice when I hit the brakes the side clearance lights come on. putting the turn signal on gives bright side marker light flashes on one side and dim flashes on the other.

One thing I cant figure out is if the engine isnt running everything works correctly, no electrical "bleed" to the other lights. But as soon as you start the engine everything starts malfunctioning.

Does anyone know where to start?
 
Check all the grounds, front and rear lights. Classic ground bad symptoms. My guess is a rear ground due to being worse with engine running in other words when the fuel pump is energized. Fuel pump off lights can ground through the pump.
 
Found ground from engine to cowl broken off. Fixed it and problem still there. Will check around and see if I can find grounds on rear.


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One more again for ground. Given after market bed I would start with chassis to bed ground chassis to lights ground or bed to lights ground. Basically, ground s from the cab back.
 
Wondering if one of the sealed leds has a diode that’s gone bad and allowing a backfeed
 
Check that the actual bed is grounded to Chassis by a dedicated strap or wire. Maybe constructed with grounds tied to the bed instead of dedicated wire.
Highly unlikely if it is very new. A lot of new stuff it ground activated. Saying that it could be in a fuse block, or some type of integrated circuit like Dodge "tipm".
 
Ron said:
Wondering if one of the sealed leds has a diode that’s gone bad and allowing a backfeed
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If the grounds check out this is another thing to check. Unplug one at a time and see if it is fixed. I've seen regular incandescent bulbs fail internally and cause weird issues too, but grounds are by far the most common, especially since none of the rear wiring is stock anymore, since the bed has been swap
 
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