Turn signal/reverse and brake light fuses keep popping!!

[Elias lopez]

long story and I’m lost at this point. So about a month ago, my right rear turn signal wasn’t functioning. I figure it’s just the bulb and replace it. Still does the same thing, solid glow instead of blinking. It didn’t blink in the hazards as well. After a couple it days it was functioning perfectly. Than by the next week none were working, fuse was blown. I would go and replace the fuse, it would last a little and than blow. Checked wiring, bulbs(not sure where grounds are located) everything looked good. Turn signal flasher has been replaced. For some odd reason the fuses kept lasting longer and longer to a point where it never blew. It last about a month and I thought it was all good. That was background info in case it could help. Now to just yesterday, my brother was driving behind me and told me my brake lights weren’t working. I check the fuse, blown. Replace the fuse, blows again. Check the wiring on the tail lights and everything as well, looked fine. Again don’t know where the grounds are. Put a new fuse in and hazards and brakes worked, all but the right tailight again. Disconnected the plug and noticed it had some dirt in there and cleaned it. Like magic that hazard and brake started working. As of right now, that problem is fixed. Now the turn signal, which barley went out today, I was driving and noticed they weren’t working. Took a frustrated drive and came back to investigate again. An interesting issue is, my reverse aren’t working anymore as well. Which I know they have the same fuse but prior when my turn signals weren’t working my reverse functioned fine(even while the fuse was blown). I do have aftermarket reverse lights spliced into the stock wiring. I took the old bulbs out and I’m just using the wiring on the trailer reverse lights. Disconnected those too see if the wiring was bad. Fuse still blows instantly when the key is turned to accessories or when it’s running. Took apart the dash to see if it was the turn signal switch that’s the issue. Unplugged it and tried again, same issue. Did notice a few loose wires in the switch but they were still in place. Seemed to be some sort of grease in the plugs as well, not sure what it was. Wasn’t a lot of anything, just a light amount. Anyways, I Looked at a wiring diagram and wanted to follow the wires to see if there was a short in the wire to the fuse panel. Noticed that fuse #9 didn’t even have a wire plugged into it, just had an empty prong. It’s a brown and orange wire for the blower motor. Disconnected the blower motor relay and the fuse under the hood to see if that was the issue, repeated the process of putting a fuse in and putting it into accessories. Same thing, fuse blows. Another note, when I put a light tester into the fuse, it does light up when in accessories. So I don’t know if this just means it’s working because in accessories or it means there’s a short in the wire. I’m not sure, I’ve been researching and watching YouTube all day yesterday and today. I’ve run out of ideas. If anybody could help it would be great. I’m running out of options and I don’t really feel like paying a bunch for it to be looked at. Sorry it’s a lot of writing, if there’s anything that needs to be clarified or added, let me know. Thanks again. I couldn’t figure out how to move this to a category so if somebody could do that, that would help a lot.

 

[massacre]

It sounds like you have a dead short in that circuit.

 

[domct203]

An interesting issue is, my reverse aren’t working anymore as well. Which I know they have the same fuse but prior when my turn signals weren’t working my reverse functioned fine(even while the fuse was blown). I do have aftermarket reverse lights spliced into the stock wiring. I took the old bulbs out and I’m just using the wiring on the trailer reverse lights. Disconnected those too see if the wiring was bad. ......Seemed to be some sort of grease in the plugs as well, not sure what it was..........

That was most likely dielectric grease, commonly used on connectors and bulb sockets exposed to moisture.

If your reverse lights and signals are truly on the same fuse, and your reverse lights still worked with a blown fuse I would suspect your wiring of the aftermarket reverse lights are backfeeding into the circuit somehow.

Are the front signals effected as well?

Did this all start after you installed the aftermarket lights? Where exactly did you tap into for these aftermarket lights?

Can you post some pictures of your wiring of these lights, or any modifications you have done to this circuit?

 

[boominXplorer]

Check any aftermarket wiring or trailer hitch wiring for damage.

If all good there pull all bulbs out and see if fuse blows with them removed. Hit the pedal and signals(with light bulbs removed and good fuse in) and see if the fuse will blow. Then start adding in bulbs till you figure out where it's coming from.

 

[Elias lopez]

That was most likely dielectric grease, commonly used on connectors and bulb sockets exposed to moisture.

If your reverse lights and signals are truly on the same fuse, and your reverse lights still worked with a blown fuse I would suspect your wiring of the aftermarket reverse lights are backfeeding into the circuit somehow.

Are the front signals effected as well?

Did this all start after you installed the aftermarket lights? Where exactly did you tap into for these aftermarket lights?

Can you post some pictures of your wiring of these lights, or any modifications you have done to this circuit?

All turn signals were affected when it stopped working. I wired them straight to the other wiring. I had issues with my reverse prior, so I cut the bulb sockets and just wired straight to the reverse. The reverse wiring is good and clean and the correct amount of voltage. It has a third wire for a ground but it wasn’t needed so I taped it off. The fuse even blew when the reverse weren’t wired in at all. So I don’t think that was the issue, thanks. All lights are currently working somehow, I went to replace the fuse the next day just to try, and it’s been working. I have no logically reason why though

 

[gmanpaint]

All it takes is a small section or wire to rub on a sharp edge, and ground itself, for the short to happen. Check your wires from where you cut the reverse lights, and added to them, all the way to the trailer connector. Heck, I would even re-do the trailer harness & connector all over again, just to eliminate it as the reason.
If you can't find a physical reason in the wiring circuits...Your computer might be going bad with a swelled diode, board crack, solder break, etc... 25 yr old tech, in a 25 yr old ride, stuff like this is bound to happen sometimes.

 

[domct203]

It has a third wire for a ground but it wasn’t needed so I taped it off.

Well that is a bit interesting...... your reverse lights most certainly need a ground. Are you saying that your aftermarket lights had three wires?

 

[Elias lopez]

Check any aftermarket wiring or trailer hitch wiring for damage.

If all good there pull all bulbs out and see if fuse blows with them removed. Hit the pedal and signals(with light bulbs removed and good fuse in) and see if the fuse will blow. Then start adding in bulbs till you figure out where it's coming from.

All it takes is a small section or wire to rub on a sharp edge, and ground itself, for the short to happen. Check your wires from where you cut the reverse lights, and added to them, all the way to the trailer connector. Heck, I would even re-do the trailer harness & connector all over again, just to eliminate it as the reason.
If you can't find a physical reason in the wiring circuits...Your computer might be going bad with a swelled diode, board crack, solder break, etc... 25 yr old tech, in a 25 yr old ride, stuff like this is bound to happen sometimes.

Thanks for the response, I re-did the trailer wiring, trucks been going good for about a day now. But I’m not getting my hopes up as this is the fix. If it doesn’t get fixed than I will check out the computer wiring, thanks!

 

[Elias lopez]

Well that is a bit interesting...... your reverse lights most certainly need a ground. Are you saying that your aftermarket lights had three wires?

Yes it had three wires, I figured it doesn’t need a ground because the negative the wire is spliced into the factory ground, I believe. I could always ground the third wire or simply splice the third wire into the negative. That’s what my brother did for his trailer brake lights, and they’ve been working perfect

 

[gmanpaint]

The computer issue I mentioned is not in the wiring from it, it is internal on the circuit board itself. These can be sent off for repair, or simply replace the entire unit itself. This is only if you can't find anything physically wrong.

If there is a wiring issue from (outside, in the harness) the computer, I would first check the power distribution box. These wires going into it, tend to get brittle and crack with age & heat.

I always say to check into anything modified or added first, when chasing an issue. To me, the first thing that pops into my head, based on what you said, is the reverse lights.

Most trailer brake lights are 3 wire, because they are also running & turn lights in one. 1 ground, and 2 positive. They are grounded to the frame, because they work on a positive circuit.
Trailer Reverse lights are a 2 wire positive circuit, with one ground to the frame, and one positive from the rigs reverse power feed.

Your rig wiring works on a ground circuit, and is why you don't see the stock lights with a ground near them, just the wires, with a ground leading back to the fuse blocks.

You only need a power wire ran to the trailer lights, from the hot wire from the rigs lights, then the trailer lights grounded to the frame. The circuit must be complete at the stock lights, for the ground loop to work. This is why they stop working when a bulb blows, as the bulb completes the circuit.

With that said, adding both the rigs positive and ground to the add on reverse lights, using the systems ground fault, might be the issue. The computer tells the grounds to be activated on everything on the truck. To make it even more interesting, there are positive grounds on 3 wire systems.

I would simply replace the stock reverse lights, and wire them to the stock harness pigtails, the way they was. If you need to run auxiliary reverse lights, just tap into the positive hot wire from them, and ground them near the mounting points. If this is not the issue, then you at least checked off one thing on the list.

 

[Elias lopez]

The computer issue I mentioned is not in the wiring from it, it is internal on the circuit board itself. These can be sent off for repair, or simply replace the entire unit itself. This is only if you can't find anything physically wrong.

If there is a wiring issue from (outside, in the harness) the computer, I would first check the power distribution box. These wires going into it, tend to get brittle and crack with age & heat.

I always say to check into anything modified or added first, when chasing an issue. To me, the first thing that pops into my head, based on what you said, is the reverse lights.

Most trailer brake lights are 3 wire, because they are also running & turn lights in one. 1 ground, and 2 positive. They are grounded to the frame, because they work on a positive circuit.
Trailer Reverse lights are a 2 wire positive circuit, with one ground to the frame, and one positive from the rigs reverse power feed.

Your rig wiring works on a ground circuit, and is why you don't see the stock lights with a ground near them, just the wires, with a ground leading back to the fuse blocks.

You only need a power wire ran to the trailer lights, from the hot wire from the rigs lights, then the trailer lights grounded to the frame. The circuit must be complete at the stock lights, for the ground loop to work. This is why they stop working when a bulb blows, as the bulb completes the circuit.

With that said, adding both the rigs positive and ground to the add on reverse lights, using the systems ground fault, might be the issue. The computer tells the grounds to be activated on everything on the truck. To make it even more interesting, there are positive grounds on 3 wire systems.

I would simply replace the stock reverse lights, and wire them to the stock harness pigtails, the way they was. If you need to run auxiliary reverse lights, just tap into the positive hot wire from them, and ground them near the mounting points. If this is not the issue, then you at least checked off one thing on the list.

Alright it’s worth a shot. An update, my reverse,turn signals still function. But my brake light/hazards fuse keeps popping. Sometimes quicker than others, but never instantly

 

[boominXplorer]

I've seen the brake pedal switch ground out and cause the fuse to blow when heavily worn.

 

[Roadrunner777]

I had a very similar issue with my right rear. I ultimately connected the right rear parking/brake bulb to the wiring for the trailer harness, and didn't go further because of weather. Logically, I got it narrowed down to a failed splice in the driver's side harness going back. My Ex is retired now, so I never got further with it. Here is a link to the adventure:

Solid-On Turn Signal - Solved