10A TAIL fuse short

Hello all,

I have an 89 b2600i 4x4. I just recently bought the truck and realized that my running tail lights, front marker lights (located next to the headlights on the corners), dash/air con lights dont work.

I checked the fuse, blown, traced the lines from the tail to the front, no signs of damage. Replaced all of the bulbs, no upgrades done to the truck, and no damage of wires behind the fuse box, and cleaned the ground points.

I bought a new light switch and replaced it in the parking lot, and the fuse still blew. So i got my $80 back and put the original back in.

The only thing i can think of is the dimmer switch, which im going to order new. I tried 2 different used ones off of loaner trucks.

When i turn my light switch once, the fuse pops, but my headlights, turn signals (front and back), and reverse lights still work. For a split second before it pops, you can see the daytime tail lights come on.

Trying not to spend 100/hour on a mechanic, but i dont want a ticket hahaha.

I have a service manual from autozone, but cant afford the actual electrical diagrams/factory service manual.

Any help would be greatly appriciated!

1992 factory manual is online, might help with your lights.

I can E-mail the 1991 factory wiring PDF if you supply your E-mail address. the 1992 service manual is too large to be E-mailed.

Yes, tail lights, running lights, and instrument cluster lights are on the same circuit - intentionally, so if cluster lights don't light, clues you as to a tail light/parking light issue/ I had to replace the headlight switch part of my combination switch once myself.

Headlights and turn signals are different circuits. I have used dimmers, wonder if you should just wire up your instrument cluster separately, as I never use the dim function (and that's what I did on my 1970 VW too !!!).

Thank you very much for the electrical diagram!

I have tried to replace my light switch, but when I installed it in the parking lot, the fuse still popped. So I returned the part and got my $80 back, so that must not be my problem. Right before my fuse pops my tail lights will flicker on, but not my dash lights. So my wiring in the back is fine.

If the summer switch didn't work, would that be able to short the circuit? Also today I was using a light tester (the one where you ground one end and touch the other end to a wire, if it gets light, it's getting power) and I got power out of both sides of the socket that is plugged into the light switch that has only 2 spades (not sure if that means anything, but I thought I was only supposed to get power out of the red and black wire, not the white and green wire). I don't get any power ever to any of the wires to my dimmer switch after unplugged.

The next thing I was thinking of doing was tearing apart the whole interior and taking off the electrical tape to follow the wires.

Any suggestions?

Thanks again!

Before assuming the dimmer switch is bad, tell us about your stereo head unit. If the factory radio illumination wire is not hooked up, and is grounding out, or hooked up incorrectly, you will pop the fuse every time.

The stereo speakers are factory to my knowledge. But, there was an aftermarket sterio "dash" (the thing that lights up red with the volume knob and radio favorite buttons). There are only 2 speakers in the truck correct? Two under the dash. I am not entirely sure what a stereo head unit though.

The turn signals idicators in my dash, emergency brake light in the dash, and headlight idicator in the dash (only when i turn on high beams. When the lights are on, there is no light symbol even though the lights are on) and 4x4 switch lights all work. The spedometer, gas gauge, and heater/ a/c, and cigarette lighter doesnt light up.

Thank you

Most people my age just call it a stereo, but for some the word covers the whole system. The head unit is the radio in the dash that usually controls the rest of the system.
So since you have an aftermarket unit, it may be wise to have a look at the wiring behind it, to see if it was installed properly.

I found this diagram and maybe it will provide some help: http://www.b2600i.com/wiring-diagrams/wd_91_b2600/wd_lighting_park-tail.htm. I am going to suggest that you check your licence plate sockets for internal corrosion. You might pull the bulbs from the taillights and license plate holders and then try putting in a fuse without the bulbs in the sockets. You could unplug the taillights to remove them from the circuit while testing. If one of the sockets has cracked that could be where your short is coming from.

Hello all, as an update, I just got around to checking the stereo and that was the problem! When it was installed, they did a poor job and when I unplugged it, everything worked perfectly (well except for cylinder 1 missfire, but that's a different problem haha). Thank you alll!!!