Short in tail lights

[suprakilla1425]

I've been blowing fuses for my tail lights for sometime now. It used to be maybe once a month or more. Today however I've blown two of them with in maybe 15minutes (driving time). I'm sure it's just a short though i'm not good at electrics. Could it be something else? If it is just a short, where do I start (taillights,brake switch). Any input will as always be greatly appreciated.

(P.S All info is in my signature) Thanks again.

 

[miesk5]

I'd look inside your pass. side tail light..lower tail gate, remove it..look at where wiring chaffs against 1/4 panel edge...our 96's wiring was about to short out after one year.

 

[suprakilla1425]

Well, I took both sides out and looked at them. I couldn't see anything that would cause a short. I decided to rewrap everything anyway just to be sure. I popped another fuse in, we'll see if it blows again.

 

[suprakilla1425]

Well, it made a 20 mile trip and just as I was trying to squeeze into a spot, the lights dimmed for a quick second and I heard a pop from under the dash. (Blew another one) I was wondering if it could be something with the brake switch under the pedal, maybe one of the lights are shorting out?

Thanks again.

 

[miesk5]

ok,

Have to isolate the short(s)

I see there there are at least 3 fuses in your 90;

1 for Turn Signals/Back-Up, 15 amp

1 for Tail Lamp, 15 amp

1 for Emerg Warning & Stop Lamps, 15 amp

Which Fuse is blowing?

To isolate; I like what our pal here, Seabronco wrote awhile ago; "...To troubleshoot the problem, you can start by disconnecting connectors one at a time until you isolate it to a set of wires..."

So, if the Emerg Warning & Stop Lamps fuse is blowing, pull da connector off the brake switch; use a Self Powered low resistance test light to Troubleshoot SHORT CIRCUITS

HERE is Chilton's TS Tips (via Auto Zone); it is a cached copyNever use a self-powered test light to perform checks for opens or shorts when power is applied to the circuit under test. The test light can be damaged by outside power.

Isolate the circuit from power and ground. (PULL FUSE/discconect BATTY))

Connect the self-powered test light or ohmmeter ground clip to a good ground and probe any easy-to-reach point in the circuit. (BRAKE SWITCH CONNECTOR)

If the light comes on or there is continuity, there is a short somewhere in the circuit.

To isolate the short, probe a test point at either end of the isolated circuit (the light should be on or the meter should indicate continuity).

Leave the test light probe engaged and sequentially open connectors or switches, remove parts, etc. until the light goes out or continuity is broken. (Or have someone shake the tail/brake/turn signal housing/wiring, etc.)

When the light goes out, the short is between the last two circuit components which were opened. .."

&

Troubleshooting with a test light

Read next Link for the important low resistance caveat....

And;

Good Info here!

A low resistance test light can sometimes be used in place of a blown fuse. The light will illuminate while a short circuit to ground exists. DO NOT use a medium or high resistance test light in place of a blown fuse. These types of test lights illuminate with very small amounts of current and can be misleading.

Circuit breakers can be used to replace a blown fuse while attempting to locate a short circuit. Always use the same current rating circuit breaker as the fuse to be replaced. A fuse blows and a circuit breaker will open when there is too high of current (too low of resistance) in the circuit. The breaker will cycle until the short circuit is removed. Manipulate the wiring harness, tug, pull, push, wiggle, the harness and listen to the circuit breaker to stop cycling. When it stops cycling, you have changed the short circuit and should be somewhere near the point in the harness where the short circuit exists

See Site for a pic of this CB

A few more guesses look @ the brake switch wiring...see if it is frayed

see if the wiring is shorted against parking brake metal area near your left foot

 

[suprakilla1425]

Yes, that was my next spot to check. And the fuse that is blowing is the hazard&stop light fuse.

 

[suprakilla1425]

Well, I went out to check out the brake switch (under the pedal) and damn near had a heart attack. I remember when I replaced the already after market CD deck with a new one and it was a nightmare as it was. (Darn thing was wired to the fuse box) But what I didn't notice was all the halfa**ed wiring under there with the trailer braking system that ws installed. All over the place was striped stock wiring with after market wires that were just literally wraped around the stock wires and taped up. So, I took off all the after market wires shrinkwraped and used electrical tape to wrap again. I looked for more bare wires and wraped them all. To my suprise there were ground wires that were as bare as a baby's bottom. I popped in another fuse and hit the pedal a few times just to see if i would blow sitting still. I'll again fill you guys in on what happens that next time I run around.

I was how ever wondering that if my voltage regulator on my alternator would have something to do with it. I'm 100% positive that it's going out and I also know that the alternator is going as well (barings are noisey) and I've noticed my lights go really dim under rare circumstances. Maybe at times the alternator is surging and it's blowing the fuse when I'm at a stop with my foot on the brake. Not sure but just a thought.

Thanks again for all the help and help in the future.

 

[Justshootme84]

If you have any kind of trailer wiring/ electric brakes, check around the rear bumper and leaf springs. I had a similar problem on the 84 when I bought it. Found where a wire was touching a leaf on the driver's-side, leaving a small burn mark whenever it shorted out and blew the fuse. I'd say 90& of the time, this problem is at the rear where a wire is touching metal, like the frame or bumper. JSM84

 

[Maddog]

Gratz on cleaning up the Bronco Abuse,, Report it. Generators/Alternators aren't renowened for putting out more voltage when they're wearing out, doesn't mean it doesn't happen. But if dude/dudet before you used it for Trailers/Snow Plowing what ever the case you might have an other then stock Alternator/Generator. Get out yer Chilton's and check the stock output voltage. Get a multimeter and check it. Get the right one in it if need be. Get her done soon because it may be stressing yer whole wiring harness..

GL.

 

[suprakilla1425]

I'm convinced that it's either something touching metal somewhere or maybe something in the brake switch may be shorting out due to the rediculous wiring. I can however make the taillights come on when I hit the energize button on the trailer brake system inside the cab. So, either it's shorting in the rearor maybe a wire that I missed got pulled out some how. Since I can force the lights on with that button, would that indicate that it's wired before or after the trucks brake switch.

 

[Maddog]

If the wiring was rigged the way say it sounds like the wires may have gotten hot and fused somewhere in the harness.. I hope that's not the case but it does happen when folks rig up stuff.

Does it only happen when your driving around? If the vehicle is moving and it's causing the problem it might just be a hot wire grounding out somewhere..

GL

 

[92bronco_in_progress]

im having an issue with the passenger side taillight to, i think its the socket, its not shorting out or blowing fuses, the bulb is good, and i have brake lights and turn signal but no tail light 99% of the time, and then it will ficker on if i hit a good bump and then back off again

 

[suprakilla1425]

I'd take the light out and look down the side of the quarter panel. It might be touching the quarter panel and shorting out. I think I've figured out my problem with mine. I followed the brake wires from the front all the way to the back. There was a spot that the stock plastic cover was gone and was rewraped halfa$$ed. It was laying on the crossmember. So I wraped it right and popped another fuse on and it hasn't blown yet. Will update tomorrow after driving some more and let yall know what the outcome is.

Thanks for all the input.

 

[92bronco_in_progress]

yeah i found the problem, cut the wiring, quick connect and eltrical tape, goooood as new