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94 Ranger tail/brake light backfeeding


wwracer

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94 ranger 4X4 4.0L I have a backfeeding problem, push on my brakes and the dash,marker lights illuminate. Also cant use my cruise control with my H/lights on, (wont engage). It used to be an intermittent problem, but it's a constant one now. Removed all the T/light bulbs, filaments look good, factory trailer wiring looks good. Any ideas ? I cant seem to find the ground point for the lighting harness, hoping a poor ground is the culprit...
 


RonD

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Bad ground is the problem with the lights, tail lights are using the dash light bulbs for the ground.

Diagram here: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_turn_stop_hazard.JPG

But not that complicated, Ford used Black wires for Ground at the rear and they should be grounded to the frame rail, so either find those and clean them up or add new ground for the black wires.

I found a '94 diagram, all the tail lights use ONE ground point on the frame, G104, so look for that
I posted diagram here: http://www.therangerstation.com/forums/showthread.php?t=162630

There also should be a Ground Strap in the engine bay for the Frame, often on/near engine mount, if you can't find one ADD one, just engine to frame.

There should also be a Ground strap on the back of the drivers side head that goes to Firewall, thats the main ground for the cab electrics, make sure it is there, often left off after engine work, and make sure it's connections are clean and tight.

Vehicle frames and body parts are painted first then bolted together, so there is no reliable grounding between these parts, and engine and trans sit on rubber mounts, so no reliable ground there either.
If in doubt ground it out, can't have one too many grounds, but can have one too few, lol.
 
Last edited:

wwracer

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2WD / 4WD
4WD
Thanks Ron, I'll look into it in the next few days. My shops full of snowmacines right now, and the floors a little soggy. Looks like I to need to find ground point G104, Ive checked and cleaned the radiator support and engine grounds, plus I ordered the proper ground cable for the truck instead of the multitude of eyelets attached to the repair post POS I have on it .....
 

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