Rear Taillight bulb burnt out/Taillight Relay?

John Keels · Post by **John Keels** » Tue Oct 26, 2004 4:56 pm

Hi I am driving a 1985 Tercel 4WD wagon at the moment with automatic. It has approximately 172,000 miles and also has the same idle/start problems that some of the other members have mentioned in the forum However, my current concern is with an electrical issue. The rear taillight on the passenger side is burnt out. I replaced the bulb in the rear taillight but it burnt out after only a few minutes operation. I believe that there is a short somewhere in the electrical system or possibly something that is grounded incorrectly. I checked the Tail fuse in the kick panel under the dash as well as all the other fuses in the interior kick panel and under the hood. They appear to be OK. I noticed on the kick panel fuse box cover that there is diagram showing what each fuse is for. I also noticed that it shows an additional TAIL labeled in the diagram that is actually above the fuse block. Well at first I thought that might be a fusible link for the taillight but it appears to be a RELAY! It was very easy to remove the relay however I cannot really tell if it is bad. Do you think that this relay may be bad and that is what is causing the rear passenger tail bulb to blow? This of course also affects the light when you brake. I noticed that when I did put a new bulb in there the brake would make the bulb light up. However, it still did not work with the lights turned ON. Shortly after replacing the bulb is when it burnt out again. What are the chances that I can simply replace the relay? Could it be something else? I recently replaced the battery in this car. The old one was nearly dead. Could this have been a factor in the electrical problem?

Thanks!

takza · Post by **takza** » Tue Oct 26, 2004 6:43 pm

You must have some wiring problems where there are cross-connxs between the brake and tail lights.

Since it's all a 12V source...I'm not sure why the tail light bulb would burn out.

I'd try to clean the bulb socket...and hit it with some WD40.

3A-C Power · Post by **3A-C Power** » Tue Oct 26, 2004 6:53 pm

I don't think it's the relay at all. The bulb will only take more wattage than it's supposed to if it's given more voltage than it should have. That would be a problem with the regulator, but if that was the case all your other bulbs would be burning too. It sounds like the most likely thing is that it was a bad bulb. There is a big difference between different brands of 1157 light bulbs. I used to use those bulbs on my moped with no regulator and some bulbs would not even last a week.

sacwac · Post by **sacwac** » Tue Oct 26, 2004 10:46 pm

I probably have the relay in my parts car... if you need it, I can send it off to you.

I doubt the dead battery could have caused a failure. The fact that the bulb actually burns out is significant in that either the quality of the bulb is poor, or the voltage is too high going to the bulb. If the wires were shorted, it would simply not turn on at all.

Speaking of brake lights, the brake light in my motorcycle recently burned out, but the onboard computer was able to sense this, and compensate by putting more electricity into the tail light circuit whenever I hit the brakes.

3A-C Power: You had a moped too eh? Mine was also unregualted, and I went through lots of bulbs... the lights get brighter as you go faster!

lesabre400 · Post by **lesabre400** » Wed Oct 27, 2004 11:12 am

I'm no electrics wizard, but I'd blame the relay - it sounds like your bulb is getting too much juice. It could also be decaying wiring (how rusty is your car?) causing a short. Relays are cheap - replace it and pull the taillight assembly out and have a look at whatever wiring you can see/reach.
I've said it before, and I'll say it again - electrical problems suck.
Good luck.

John Keels · Post by **John Keels** » Wed Oct 27, 2004 8:03 pm

Thanks guys for all your help. Tomorrow I am going to buy a new taillight relay for the car and put a new bulb in the taillight. I just needed a little input.

Talk to you later,

jkeelsnc@yahoo.com

dug320 · Post by **dug320** » Sat Oct 30, 2004 10:44 pm

Think of it from another perspective. You can not get more than 12volts. If the light bulb burns out it cannot be the voltage. If there was a short, the fuse would burn out. If it is the relay it would not work on the drivers side. The amperage could be the cause but that would be a very odd.

I would try another bulb.