Need help with a wierd tailight short that is boggiling my mind.

[JESSEGG]

Maybe somebody can help me troubleshoot this. I have owned this vehicle since March and have come across and solved many problems thanks to the assistance of this forum.

Currently, my rear drivers side running light and marker light keep blowing the 7.5 amp, position 40 in the fuse box. I can't figure out how to trouble shoot this.

After I replace it, it works until I turn the car off and then the fuse blows. Now that being said, the front drivers side marker is missing since I bought the car (noticeable in my profile picture).

Can anybody advise me in the best way to troubleshoot this? As always thanks in advance.

Jesse

[mikepellegrini]

High tech way is to inject an RF signal and then pinpoint the break with a directional receiver. The receiver looks like a wand. You just wave it over the car and it beeps when it finds the break.

You might find a rental place that had one of those. Very nifty.

[mikepellegrini]

Here: YouTube

[rhett]

Just looked at the wiring diagram and it seems straightforward. However, being here in the UK I am not sure how the marker lights are supposed to operate (we don't have them), do they stay on all the time the car is 'on' and what is a 'running light' and how does that operate?

For the fuse to blow you must have a direct short from any of the light circuits involved, but I do find it odd that a fuse blows when you switch the car off? Can you confirm this, or does it actually blow when you turn it back on again?

I would open up all the running and marker lights on the driver side and check for a short in the wiring or the bulbs themselves...obvious first check would be the missing marker light at the front.

If you could provide a bit more operational info we should be able to help track this down..

[JESSEGG]

Thanks Rhett, i will clarify and excuse me for my ignorance.

You are right, the fuse pops on the next start. When i say "running light" i mean the 2 tail lights that are on when you are driving with the headlights up.

On my vehicle the 2 very right rear tail lights illuminate when the headlights are up and on as well as the 2 rear markers on the quarter panels. My vehicle doesnt have electrical to the lower center bulb positions (beneath the brake lights).

As I mentioned, the front marker light is missing. As shown in this image. Please let me know your thoughts or if you need more information.


Thanks

Jesse

[emoore924]

Could the start circuit be energizing something it should not?

After you've replace the fuse, when you turn the key to on, but not start, does the fuse blow then, or only when you engage start?

[rhett]

^^ Yep, I'm thinking along similiar lines too. So, the fuse blows at some point when you start the car, we need to know what that point is. Is it as above - or only when you switch the lights on?

Then, once it has blown , what conditions are there for you to replace the fuse without it failing straightaway? Are the lights on at that point, is the car running, and so on..

It seems that a particular set of circumstances are operating here, so to help we would need a complete 'blow-by-blow' account of what you do and what happens. If you could step through the process with your observations, I am sure we can get closer to the problem.

[ckelly78z]

I had something similar that would blow the fuses even after I replaced the rear wiring harness. My problem was a pinched, therefore grounded out wire that would blow upon turning on the key to get power to the lights. Clean all your grounds and check wire continuity.

[Tom944]

Check the wiring at the missing marker for a low resistance short. That combined with inrush to a cold bulb could blow a fuse.

[JESSEGG]

Ok guys sorry for the delay, just made it to my Friday. If you replace the fuse and start it up, turn the lights on it works. It blows when you turn it off. I figured that out because Johnny law pulled me over tonight in a gas station, let me off with a warning and I popped the hood and put a 7.5 in position 40, drove 40 miles and the left rear running light stayed on the entire time AND the left rear marker. Now it is blown again.

[JESSEGG]

SOLUTION, FIGURED IT OUT..READ ON: Well it took getting pulled over by Johnny Law to investigate it, and you fine group of folks with your advice that helped me troubleshoot it.

Johnny Law was a motorhead, so he was more interested in the vehicle then writing me a ticket. I told him I had a short that I couldn't figure out so he was cool..then right after I said that I thought about what Tom944 mentioned about checking the marker light. I asked the cop to shine his flashlight by the missing marker light in the front drivers fender. I reached in and looked at the boot, apparently the previous owner had the power/ground touching each other. I separated them, replaced the fuse right there in the gas station he pulled me over in and It went on. The marker and rear running light has been on ever since. Thanks guys!