Dome lamp ground short circuit questions.

[Grit dog]

So but of a different issue.
What I do know:
I understand how the circuit works for the dome/courtesy lamps.
They worked with Headlight light switch But door jamb switches were non op. Those have been replaced and are working. Headlight switch replaced as well, as it appeared to contribute to the issue

The circuit gets a random “partial” ground short somewhere in the wiring. IE dome lamp will light up at half brightness without being activated by any of the 3 switches. Then full ground if switches are activated.

Tells me there is a “Live” short in white ground wire somewhere. IE ground wire is grounding somewhere it shouldn’t. However this is not intermittent. It may be shorted for days( consistently) and then work fine for days (consistently).
I’ve been able to move, wiggle or verify the wires coming from the dash thru the drivers door sill and up to the dome light. They’re in tact and or don’t cause a change in condition when pulled or moved around.

I have not been able to locate the wire from the Passenger jamb switch but have pulled on it thru the door jamb with no change in condition.

At a bit of a loss. No wire damage in the “typical” areas, and generally the wiring and systems are very clean on this truck.
Suggestions?

 

[Grit dog]

The perplexing part is it doesn’t appear like a chaffed wire that is just rubbing and grounding out. this truck does not ride smooth and the condition is either present for a period of time or not. It doesn’t change or flicker as the truck bounces down the road .
When it is happening, checking continuity white wire to ground is a consistent 10-11ohms resistance. Goes to zero when switch activated to ground

 

[75gmck25]

The orange and white wires run under the metal door sill on the drivers side, and both the copper inside and the insulation outside has become extremely brittle in that area. The exposed wiring running up to the dome light seems fine, but I’ve repaired wire under that door sill at least twice. I would check there.

Bruce

 

[Craig 85]

I had an issue when I installed the new door jamb switches. As I tightened the switch into the body, the wires got twisted up and were causing a ground issue. IIRC, I held the plunger on the switch as I tightened it to prevent the twisting of the wires.

Also could the plastic between the terminals have broken causing the wires to touch?

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[SquareRoot]

Is your done light housing chrome plated plastic, like the aftermarket ones sold by LMC?

 

[Grit dog]

Thanks for the suggestions guys.
I pulled up the carpeting and cleaned out the door sills and the wiring is all in one piece, not cracked, and even with this opened up and wires not touching any metal to short out, it was having the partial short condition at that time.
It actually started acting right after i buttoned everything up and then today it was shorting out all day.
I may just replace the wires through there but it looks like new.
@Craig. New door buttons and they were rotating, not cranking the wires out of shape. I removed both after installing to check and pre rotated the wires several turns before threading back in. Condition was identical with the old door buttons except they weren’t grounding out so they didn’t work at all. Probably just corrosion in the threads.
removed the dome light from the roof. Wires in good shape and with nothing touching metal, it was still partially grounding out.

Got a LED bulb so at least it doesn’t get hot and won’t kill the battery Quickly if I happen to leave the bulb in.

 

[Grit dog]

Is your done light housing chrome plated plastic, like the aftermarket ones sold by LMC?

yes it’s plastic. Looks original, but idk. It’s a little melted from this light sticking on in the past. Before I owned it.
OP put a battery disconnect in it instead of pulling the light bulbs from the courtesy and dome lights, lol.

 

[AuroraGirl]

yes it’s plastic. Looks original, but idk. It’s a little melted from this light sticking on in the past. Before I owned it.
OP put a battery disconnect in it instead of pulling the light bulbs from the courtesy and dome lights, lol.

do you have cargo lamp? i believe it wires through the switch on those equipped

 

[AuroraGirl]

do you get a brightness difference when door is open on both/either the dome/floor vs using the switch.
such as turning knob would not make them brighter or dimmer when it clicks "on"?

my driver side wiring... is cheese because i dont have a floor and they yanked out or broke or something, and only passenger switch turns on lights. but the lights are not bright if i use headlight knob, if i open the passenger door (with knob off and on) i get full brightness.
im thinking an old headlight knob + broken wiring causing a grounding issue.

if that perspective helps you check for other functions, cool.

headlight switch shows wear in other functions, so if yours is showing wear it may be a good shot to replace anyway

 

[SquareRoot]

I bought a new bezel (chrome plated plastic) and had a similar issue. Drove me nuts! Discovered the bezel is conductive via the chrome plating. The metal tabs that snap in and hold the bulb were intermittently touching the bezel. It was a head scratcher.

Just something to check.

 

[Grit dog]

^ That would be a real mystery.
Yes it's plastic and I considered that maybe it was somehow grounding out through the housing or mounting screws, but I disconnected the dome lamp housing and let it hang clear of the metal cab roof as well as the courtesy lamp housing and the condition still persisted.

Yet this morning popped a bulb in and it's shorting, but wasnt last night when I pulled it into the garage. Truck literally hasn't moved.

 

[Poppy 87]

2 things I would verify: correct bulbs are installed and terminal tension in the fuse block. If okay, I would perform parasitic draw test and isolate each branch of the circuit(s) to determine exactly where the short is. Good luck

 

[Grit dog]

Bulbs are correct. And it’s not an issue with the + wire. Have 100% of battery voltage at all times whether issue is present or not. It’s an issue with the ground.
I’m sure you’re aware but there is constant power to the lights and a normally open ground circuit that gets closed by any of 3 different switches. Door jambs or headlight switch.

Maybe I don’t understand what I would test for parasitic loss?
thank you for the suggestions and help

 

[Grit dog]

Nother question, presuming it HAS to be in one of the wires.
Does anyone know where the junction is from the switches to the lights? Truck has AC so less visibility under the dash.

Find that, I can isolate each switch lead and each of the 2 leads going to the lights. Or maybe the junction block or connection is shorting to ground?

 

[SquareRoot]

I'm betting it's your headlight switch. That provides the third ground option (doors are one and two) . Make sure you have a good ground from the ground buss under the dash to the light switch. It's the extreme position on the rheostat that grounds to turn the dome light on. If that's an old switch, it's bound to be worn out internally.