Taillights eating fuses
 

So I have an 87 Runner, and right now my tail lights (and dash lights - both on the same circuit) are eating fuses. I'm on my second fuse in a week and I've made sure I'm using the right amp rating. Anything that would cause it to do this? I don't have any items added to the electrical system (radios, etc).

Thanks in advance!

You have a bad ground or shorting somewhere in the wiring. Maybe aged wiring or wet circuitry. OR!! Somewhere wires are crossed.

Does your truck have a tow package or trailer light connector? IF so, it will have a little converter somewhere that may be shorting out and blowing the fuse.

X2 on the short. That is the one thing that I am sorting out on my '81, 25+ years of other people's ideas of how electricity should flow...
Here is a link to a downloadable Service manual, 85-94 Pick ups and 4Runners are the first one. It is a 60Meg file but might be worth the time to down load as there should be a wiring diagram that will help you chase down your gremlins...Good luck!
http://www.ncttora.com/fsm/index.html

Bad Ground!!! BAD!!!:spank:

Thanks for the input. I'll try and track it down. Thanks also for the link to the FSM... i've been looking for one for a while!

Thanks!

1. Check the bulbs themselves. Remove the bulb from the socket, look at the contacts for meltage. Look inside the socket for meltage as well. Old 1157 bulbs will melt and short the sockets.

2. check/remove your trailer connector. They often fry, or it could be your trailer lights that have shorted out or are damaged.

HTH.

1. a bad ground will stop the lights from working but will not blow fuses. A short to ground will.
2. the 5 wire to 4 wire trailer light converter, if you have one IS the most likely culprit, unplug it or cut it off and tape the wires. Follow back from your trailer plug to find it.
3. the notorius taillight bulb sockets are not so bad on 4 runners but could benefit from some rust check or similar stuff routinely.

Good luck!

change the bulbs if you haven't already, just $3 to eliminate that as a possibility. a bulb could be grounding out. check the taillights for water getting in, and grease up the socket if necessary. are they 1157 bulbs, i can't remember off the top of my head. if so, make sure they're in the correct way too. double filament bulbs can go in backwards if you're not careful.
always good to make sure your battery terminals are clean and tight too. last time i had to troubleshoot a short, i swore it was either my brake light circuit or the amp in the trunk, and started pulling all kinds of stuff apart, and it turned out to be a loose negative terminal. i still haven't rehooked my subwoofer amp since i yanked it out to eliminate it as a possibility. hope you find it soon

short
 

You said you are on your second fuse in a week. This leads me to believe that the fuse doesn't blow right away. Is this true?
If so then there must be an intermittent short.
I igree it is unlikely, but not impossible for a poor ground to cause the problem.
Poor connections tend to raise current levels and cause excessive amp draw and heat. Sometimes too much for a fuse to handle over time.
However I would be looking for chaffing of wires.
You can also replace the fuse with one of lesser value and see if it pops right away, indicating a constant but low draw short. If not drive the vehicle over a bumpy road and see if that aids in popping the fuse with the lights on.
Intermittent problems can be difficult, but fun and interesting to track down.

I'm having a similiar problem. I haven't driven my truck at night lately so I didn't realize my taillights, brake lights and cluster lights don't work. I looked in the fuse block down by my feet and sure enough the 15 amp STOP fuse was blown. So I replaced it and I got my brake lights back, and I got my cluster lights back, but ONLY when I pushed the brakes, and they were very dim. Still no taillights. Since I was driving at night and didn't want to get pulled over for no taillights (and also didn't want anybody to run into the back of me), I kept my foot lightly on the brake, just enough to cause the brake lights to stay on. This lasted for about 10 minutes, until the 15 amp STOP fuse blew again. Think mine could be caused by a short as well? I haven't messed with any of the wiring in a long time.

Rob

X 2 :good:

A poor connection raises the resistance in a circuit, reducing current draw. The only thing that pops fuses is excess current. A poor ground cannot blow a fuse. Scrid is right that you're looking for a short, and it's likely chaffed wires or a bad trailer-light integrator (these are horrible).

Possibilities;
Wrong bulbs in the tails? They could be drawing too much current.
Trailer wiring? Could be chaffed against the hitch, frame or body.
Integrator? Internal shorts in these badboys cause trouble.
Lastly: Integration relay? My 2nd Gen Runner has one in the drivers kick panel area, and it's been a headache. The body seams have leaked over the years, allowing corrosion to get into the fuses & wiring. I've lost my tail lights too but haven't diagnosed it yet. Probably just going to rip out the factory fuse box and build my own.