crossy

HAS ANYONE HERE EXPERIENCED THIS EXACT PROBLEM ?. If so maybe you save me a lot of troubleshooting. The dash lights keep going out and that takes out the rear park(running) lights only. I still have ALL front lighting & my brake lights. I also have a working dome light by the door switch, but not by the headlight switch now. I mean I know I have a hot going to ground, but just wondering if anyone ever found that the high beam switch(column stalk) or anything like that was causing it. I have put TWO other headlight switches in it to no avail. I already suspect that some wiring running under the floor mat, or down the frame,to the rear lights, may be grounding out(rubbed through). I can't remember what color wire the running lights are. thanx , crossy

j_martin

The dash lights and the tail lights are on the same fuse. Usually this sort of problem is either a short in a tail light fixture, or a short in trailer wiring. I've also seen the main harness going to the back pinched by the spare tire and shorted.

Problem's probably not up front, but underneath/in back.

Tail light wiring will be either brown or black with a yellow tracer.

BTW, find the fault and verify it. (diagnostic) before you throw parts at it. It is the fastest and least expensive path to a repair.

This one is easy to trouble shoot. Tug at and wiggle things till the fuse blows.

crossy

the fuse blows as soon as the headlight switch sends power out(pulled on)

so mopar wiring follwed the standard trailer code of brown is running lights.lol. Think i'll find that brown wire at the back and check continuity to ground. I'm sure it will be :-( . No trailer wiring, no spare tire. factory radio delete, (Naval base truck) Thanx , crossy

j_martin

Same power line goes to the parking lights in front, and clearance lamps if it's a 1 ton. Radio and heater switch lights should be on the dimmer.

There's enough lamps on it so it will probably be only a coupla ohms to ground when it's good.

Even if the dash is shorted, that circuit goes through the dimmer, so if the **** is turned all the way counter clockwise, it shouldn't blow the fuse.

Here's a trick. Take out all the parking lamp bulbs, clearance lamps if they exist, and turn the damper all the way to the left. Using 250 tab connectors, wire a fairly hefty (back up lamp) light where the fuse should go. Wiggle things till the light dims or goes out.

PADuallyBoy

I've had that same issue before. Ended up being the wire that run through the tailgate hinge rubbed through and we're going out. It would only blow the fuse occasionally if I hit a bump. I actually found it when I was walking in the bed and then on the tailgate. This is on my dually, idk if you have the marker lights across the tailgate or not, but I'd check there if you do. They run through the hinge on the drivers side.

u2slow

Check the wiring that runs along the drivers door sill. Between being trampled on and a soggy floor liner/carpet its a rich environment for electrical issues.

I recently undid a floor mounted high-beam switch on my '93... now fuses don't pop, plus the tach and heater control lamps came back on.

crossy

OK, so I was able to back on this thing today - The wiring I mentioned that runs under the floor mat is for the inside of the truck only and since the Dome still works by the door switch i eliminated that from the problem. Since it is just the instrument lights and Running lights that go out. i disconnected both harness connectors from the back of the Gauge cluster, FUSE STILL POPPED----i disconnected the WHOLE rear section of the wiring at the weatherproof plug near the ABS valve on frame. That eliminated ALL wiring on the back of the truck. FUSE STILL POPPED.--- tried another known good headlight switch, FUSE STILL POPPED-- the only wiring left is from the switch, through the firewall and down the length of the frame , I physically separated it from the clips and got it off the frame everywhere,FUSE STILL POPPED-- . about all that is left is the wires that run to the front parking lamps, which i didn't think were out originally, but i guess they were. The turn signals work front & rear. . I am posting this for anyone doing a search for same odd issue.
BTW- the running light wire is brown with a green stripe. Crossy

j_martin

Did you remove the light bulbs from their sockets? Though rare, it is possible for a bulb to short internally. (usually in a damaged base)

It's also possible for 2 wires to be shorted together inside the loom. Usually there'll be some visible evidence of over heat all along said wires. There's an in harness splice in this circuit about 6 inches from the headlight switch that could overheat if the crimp isn't perfect or there's ever been some moisture near it.

There also might be a harness leg with this circuit near the left kick board (for clearance lamps) that could get tangled up with the parking brake mechanism.

crossy

Def couldn't be bulb shorted out as ALL running light bulbs are disconnected at harness still- the only bulbs now are what I mention below is anything else that lights on the dash other than the gauge cluster which is also disconnected. Alright get this . I found plugs for every separate wiring harness, I unplugged the wiring that runs across the floor,to all the front lighting/horns also,FUSE STILL POPPED. So then i found a large gray connector to ritght of steering column that several other smaller connectors go into. I unplugged all 4 of them, STOPPED popping fuse. those wires feed many things that may also be 'lit' by the instrument lighting power, but as i plugged them in one by one the fuse did not pop. I wiggled and moved all the wiring, but could not get it to pop, there is something grounded out that that one of those 15 or so wires feeds. all four of those of those plugs and the 18 or so wires associated with them come out of the steering column. This truck doesn't even have pulse wipers, much less cruise control , and yet there are 18 wires coming out of the column!!!

j_martin

Does the halo light work?

crossy

If you are talking about around the key? this 89 does not have that .

So I had the entire harness nearly out of the dash, I found several LUMPS ,like a snake that just swallowed a bullfrog. there was a spot where the factory solders 3 orange wires to 2 other orange wires and they did a horrible job. there were sharp ends that had chaffed out of the friction tape. I fixed that and covered it with self-sealing silicone tape- figured I should fix others lumps too, but they weren't solder joints. The whole time of re-assembling all the dash & components, I had the park lights on and the fuse did not blow, UNTIL I reached underneath at the very end to plug in the radio antenna. WTH? - anyway, I called it quits. I can live without a radio for a few days until I feel like getting back to it. The CD player works! at least I have all my lights as long as I don't plug in the antenna. I don't know if this is an antenna issue or an internal radio fault. But after an entire day of chasing this demon it's just good to know I got to the bottom(s) of it. thanx,Crossy

Jim Lane

When did this electrical problem start, was everything working fine before?

Have you installed LED 's in the dash or marker lamps?

Some wedge base LED's will cause a dead short if inserted into a standard socket.

Also installing a single contact bulb like an #1156, into an insulated base socket, #1004 lamp (dome light) will create a dead short.

Here is a trick I use to find shorts in auto/ tractor trailer wiring.

Remove the fuse that keeps blowing and install a 5-10 amp self resetting circuit breaker using test leads, now using an induction ammeter, telco induction tone set or even a magnetic compass follow along the wiring harness watching the needle, it will have a distinct deflection every time the circuit breaker cycles, as you are following along the wire with the needle flicking and it suddenly stops, investigate, you have usually found your short to ground.

I have used this to find a lighting circuit with a dead short, the wire was riveted/pinched behind the engine bulkhead on a new 50-foot transit coach, I followed the signal right through the aluminum body panels and right to the short.

The circuit breaker is turning the wiring into a crude radio transmitter and you can follow the magnetic pulse until it goes to ground.

This is what an induction ammeter looks like, a simple but valuable tool to diagnose electrical problems.

induction ammeters

I also used these to check starter problems on Detroit's drawing around 1000-amps.

Jim

sooty

jims 1156, as a tool, simpler (cheaper), but more work, connect a "in socket" 12 volt bulb, (any bulb handy will work) to the fuse connection, where you can see it above the dash, a dead short will keep the light bright at full intensity, with all the exterior light loads disconnected, start wiggling the harness near connectors and splits, behind dash, anywhere you consider it could fail, with visibility of the bulb activity it will flicker when you are close to the affected area, and go out, once the short is located and fixed.

sooty

I meant to add, saving lots of fuses...

crossy

I need to replace the antenna anyway, AFTER I do that, if I touch the back of the radio and it sparks AGAIN, I will know there is a short to case inside the radio. Radio IS indeed wired correctly. for now , i'm done. haha, thanx again , Crossy