CHASING DOWN A SHORTED WIRE
Posted: Fri Feb 02, 2018 5:46 am
A while back, my '03 Hilux 4x4 unexpectedly blew a fuse in the taillight circuit. This circuit controls the dash lights, taillights, and license plate lights. I replaced the fuse, and it worked for a few days and blew again. I hooked an ohmmeter into the circuit, and it looked normal. So I took the truck for a drive on our rough dirt road with the meter connected, and every so often it showed a dead short.
I decided to try and figure out the problem. I have a downloaded Hilux manual. It took me several days to decipher their schematics, but I started out by opening up the relay and fuse box under the hood. This is where the taillight fuse is located.
This is the rat's nest I found when I finally figured out how to open the box. The wire from the taillight fuse had gotten hot, and was fused to several other wires. I separated them and it looked like none had shorted. Just to be on the safe side, I ran a new wire from the box to the junction box inside the cab. This was a real ordeal, because figuring out what went where in the J/B using the Hilux manual schematics was almost rocket science.
Took the truck on another drive, and the short still showed up intermittently.
At this point I panicked. If the short was under the dash, it would be hell to find. So, I started at the taillights and worked forward. I removed the passenger seat, lifted the carpet, and disconnected the junction connector to the rear lights.
Another drive showed that the intermittent short had disappeared. Checking the resistance at the terminals in the junction connector showed several wires were very close to ground (less than 2 ohms.) At this point I removed the taillights and the license plate lights and a recheck showed the low resistances were still there. I unwrapped the front part of the harness and found the taillight wire and its ground wire had gotten hot and were almost completely fused together. It looked like I needed to pull the entire rear harness, and this meant removing the gas tank.
Finally got the entire harness out and unwrapped. Three wires were completely fused together: the taillight power wire, taillight ground, and left hand turn signal power. I replaced these wires, rewrapped and reinstalled the harness. Everything checked out ok, and after 2 weeks, no more problems.
It took me 1/2 hour to do this writeup, but almost a week to find and fix the problem. A lot of work, but on the plus side I now have a real understanding of my Hilux's electrical system and I know how the Hilux manual works too.
- JAMES
I decided to try and figure out the problem. I have a downloaded Hilux manual. It took me several days to decipher their schematics, but I started out by opening up the relay and fuse box under the hood. This is where the taillight fuse is located.
At this point I panicked. If the short was under the dash, it would be hell to find. So, I started at the taillights and worked forward. I removed the passenger seat, lifted the carpet, and disconnected the junction connector to the rear lights.
- rear wire loom.png (308.63 KiB) Viewed 1680 times
Finally got the entire harness out and unwrapped. Three wires were completely fused together: the taillight power wire, taillight ground, and left hand turn signal power. I replaced these wires, rewrapped and reinstalled the harness. Everything checked out ok, and after 2 weeks, no more problems.
It took me 1/2 hour to do this writeup, but almost a week to find and fix the problem. A lot of work, but on the plus side I now have a real understanding of my Hilux's electrical system and I know how the Hilux manual works too.
- JAMES
