Tail Lights Mysteriously come on when car is parked

nissan
300zx

#1

My son has a 1985 Nissan 300 ZX. The car has practically been rebuilt. Several mornings a week the car is dead. We have replaced many major car parts over the past 2 years like the ignition switch, alternator, battery, clutch, rotars, brakes and breaks. We even pulled the fuse to the security light as that was drawing many amps when the car was off thinking that was what was causing the dead battery. If I had not seen this with my own eyes I would not believe it. The car will be parked, shut off for hours and the tail lights mysteriously turn on. The headlights are not coming on, just the tail lights They just slowly come on. We have witnessed this 3 times and have no clue what the problem could be. We walk over and turn the lights on then fully then off. However, the lights are in an off position to begin with. Any clue?


#2

I would think the headlight switch or a relay would be the most likely. The age of the car also makes corrosion inside a wire connector a possibility. Corrosion of terminals and wire from water intrusion can make a conductive pathway between a terminal with power and the tail lamp circuit.

Examination of the wiring diagram will reveal if there is a relay involved with the parking lights, that would be a good place to start either replacing or temporarily unplugging.


#3

Thank You we will try that. WE have spent hundreds of dollars and still no one has been able to fix it. I think I will take this information and give it to my sons Auto Tech teacher and maybe they can make it a project in class.


#4

Good luck and keep us posted.


#5

If the rear lights are controlled by an electronic module I would suspect it is causing the trouble. If the lights are just switched on through the light switch then I suppose the switch might be at fault, but I doubt it is, going by the way you describe the way the trouble happens. If there is a towing hitch wire harness on the car look for signs of corrosion on the connector. Check for signs of a bridged connection to power under the fuse panels. This sounds like a water corrosion problem in the wiring.


#6

All good comments but I had this problem before and oddly enough it was a '94 Nissan Sentra GXE. It turned out to be a bad brake light switch. The next time the lights come on just unplug the brake light switch. If the lights go out…install a new brake light switch and make sure it’s adjusted properly. My tail lights would go out if you stepped on the brake or turned the headlights on then right back off.


#7

My first reaction was the brake light switch as well. That would be a cheap and easy fix if so.


#8

I agree with the corrosion possibility. Those cars were rust buckets and everyone I have met had corrosion problems with them.


#9

I would also vote for a defective brake light switch. I remember our neighbor had this problem on their brand new 1949 Chevrolet the day after they brought it home. It went back to the dealer for a new brake light switch.


#10

When I wrote my first response on this I wondered about the brake lights being the problem but assumed the OP was sure about which lights had the trouble. After what @Missileman stated I also agree it is the brake light circuit that is having the trouble. If the running lights circuit was being effected then the front lights and dash lights should also be turning on as they are all normally connected together. It may also be that the brake switch just needs to be adjusted in order to stop this trouble. The brake pedal might be moving slightly downward over time just enough to turn on the switch.


#11

This is really weird because I am actually having the same problem but it’s not just my tail lights. My side marker lights also come on by themselves too and have had dead batteries because my light feel like coming on during the night time. if anyone could please help my problem too it would be much appreciated! P.S. my car is the same exact year too…maybe bad year or just coincidence.


#12

The side and taillights are most likely tied together so it would be normal for both of them to light up when power is getting to the illumination circuit.

I think the advice @rattlegas gave about a corrosion issue causing the problem is perhaps spot on. The first place to look for that type of problem is under the fuse panel that is under the hood. Now since the lights you are having trouble with have to be turned on with a switch inside the car that seems to point to the trouble possibly being under the dash. Perhaps the dash fuse panel. Unless the light switch itself has a problem, which I doubt, then power is getting applied to the light circuits by another source and after the switch. One thing you can do to help you find which circuit is providing the power is to remove fuses in the panel under the hood, one at a time, and see which fuse makes the lights go out while the trouble is occurring.

Another possible area that could be providing the power to the lights and causing the trouble is a security system, if there is one installed.


#13

I actually think it could be my headlight switch by it self. When the lights come on by themselves I can nudge the headlight switch with my hand and the lights will suddenly turn off. So in conclusion, I believe it’s the switch. Correct me please if I could be wrong.


#14

Would have been helpful to mention that in your original post. Yes, get the switch checked out and replaced, if necessary.


#15

What you say about the light switch does make it seem the switch is very likely to be the cause of the trouble. If you want to prove it before you replace any parts then try removing the connector to the switch while the trouble is happening. If the lights go out, you have proved that the switch is at fault and current is flowing through it, most likely due to a dirty conductive connection.