Celica Forums General Discussion Exterior Tail light fuse keeps blowing

Hey guys, new here but not new to owning a Celica. I have a 2005 Celica and recently I've noticed that when I switch the headlights on, the tail light fuse blows. I've tried changing the bulbs, swapping the fuses, and I swapped the tail light control relay(it was blown too) and it still keeps blowing. I had it checked by a mechanic but they couldn't find the issue after pulling the center junction box and checking the wiring there. Not really sure where else to check, I know that one of the front side maker light's is damaged in that the wire is ripped, that's where I'll be focusing next. Any clues on where else to check?

Ok, here's a few ideas to check to make sure your on the right track. First I would get the owner's manual and check to make sure all your fuses are correct. Buy extra fuses if you need to, just in case you blow another fuse to replace. The next thing I would do is a battery/jumper wire method with a multimeter. Here's a video showing you how to check for a short in your circuit and which fuse to start your investigation.

Now understanding your front side marker is damaged, go and check to see if there's any grounding wires touch the car's fender. Once you find the exposed wires, hook up your multimeter to the exposed wires and see if that's where your short is coming from once you switch on the headlights. If you see the multimeter dc volts go up, you found your problem.

The OEM Celica tail/brake light is dual filament incandescent 7440.

I replaced them with a LED bulb in the original socket, bought from China via eBay. One is fine, one bulb's wire got hot and burned, melted the socket. It did not blow the fuse and worked well for a couple years. One license plate wire had cracks along 6 inch length.

Eventually I had a short somewhere, tail light fuse blew. A craigslist guy wanted $150 diagnostics then more for repairs. I did not want to spend that money, guessing the shorts are easy to find, went in trouble shooting, replacing the 7.5 A with a 30A so the bulbs stay on long enough for me to find the short, but it overheated, burned and melted the fuse panel, blew the Body Control Module which costs $1,100 at dealer. Most other light bulbs and body functions went kaput, only front head lights and power windows were working. I spent lots of time in many days trying to find and fix the problem to no avail, causing more serious damages. Damn stupid. I was able to buy an used BCM/Fuse panel in eBay for $70.

I suspected a branch of wire harness was shorting inside the hatch's channel, was about to cut wires, pull it out and check for shorts, finally I wised up that I had no tools, did not know how to remove the rear defrosters' terminals without breaking. I called my trusty mechanics, he referred me to a local chassis electrical guy. He said $95 to find and fix the short. He installed the new BCM, things started working again. He looked at the tail light wiring and took out all body plastic panels, found the tail light wire had insulation completely melted along the whole length and a burned out spot behind the panel at the left passenger side. The guy who installed the digital video camera took that panel out and could likely have pinched the wire against the chassis, but that wire is also in the middle of the harness, so who knows.

Repair guy found the tail light wire got hot enough to melt and burn off insulation all along its length. He also found the license plate bulb's insulation brittled, cracked and open in a length about 6 ", could only be caused by heat. This tiny LED bulb supposedly draws very little DC current. I cannot explain why it got so hot. He had to unbundle the wire harness and run a long replacement wire from the burn spot to the fuse box under the dash. He said he found lots of problems with LED bulbs. He repaired thousands cars and should better than I. He replaced all rear light bulbs with incandescent. I paid him $200 total for the extra work. This guy is good and honest, recommended.

Any bros has bette rundersatanding of this LED problem, would be interesting to know.