Tracking down a short in the wiring??

[bfloyd]

Noticed this weekend on my way home from work, I had no tail lights on the LH side of the car. Thought it might be a loose bulb, so I proceeded to get the screw driver out to remove the tail light assembly. While I was back there, I noticed the left side license plate light was out too. Walking around the car, it's the entire left side. No left side marker lights and no parking light in the left side of the front bumper. Turn signals and brake lights are fine. All of this points back to FUSE #2. I pulled the interior parcel shelf panel to expose the fuse block,and indeed fuse 2 was blown. When I replaced the blown one for a new one, the new one immediately blew. Headlights and everything was on at the time.

The only electrical work I've done recently is to replace the left front fender side marker light socket that was corroded. The original bulb had rusted in place and I simply ordered a new socket and spliced it in. I haven't checked to see if anything behind the fender has come loose, but I seriously doubt it. It was all heat shrinked pretty good when I replaced it. I did have the car up at DMC Midwest about two weeks ago having some service work done, but none of it was electrical.

Any clues of how to find this?

[sdg3205]

unplug the black molex connector from the engine bay bulkhead. That will eliminate 50% of the car (entire rear). You can always use a multi meter across the fuse terminals if you want to save fuses.

If it blows again, the problem is up front. If it doesn't, it's most likely somewhere in the rear fascia.

[iflights]

You didn't mention if the left side was working after you replaced the side marker socket? My money is typically on the last item repaired as being the culprit but I don't know enough details on this.

[David T]

You didn't mention if the left side was working after you replaced the side marker socket? My money is typically on the last item repaired as being the culprit but I don't know enough details on this.

Without special tools it can be difficult to find the actual short. One tip is to remove the fuse and temporarily wire in a bulb. If you have a short to ground the bulb will light up. Go searching and when you find the problem the light will go out. Typically it will not be the wiring harness itself, it is often a device connected to it like a light socket. First thing to do is unplug the taillight board. Examine each bulb. if someone put the wrong type bulb in or installed a bulb incorrectly it can cause a short. Some of the bulbs have 2 pins, each at a different height. If the bulb is installed the wrong way it can cause a short. It is possible the harness got pinched somewhere. The divide and conquer method in post #2 is a good strategy.

[bfloyd]

You didn't mention if the left side was working after you replaced the side marker socket?

I thought the same thing, but I looked back through some photos of the Brad Paisley video shoot I did with the car several weeks ago, and everything was lit up. So whatever has happened, has happened in the last two weeks.
I'll definitely unplug the black bulkhead connector to eliminate half the potential issue. Never thought about doing that.

[Gregadeth]

Same thing happened to me when I was replacing all my lights with LEDs. It was the wiring at one of the license plate lights (which is pretty flimsy) so you may wanna check that also.

[bfloyd]

Ok.... Unplugged the black molex connector from the rear bulkhead and the fuse still blew. Plugged the rear back in and proceeded​ to the front of the car.

I unscrewed ​the left front fender marker light and unwrapped the electrical tape from the leads. No exposed wires in there. Cut the heat shrink wrap off the marker lamp socket leads and everything was good there.

Next, I put a light up clip on tester into the #2 fuse slot. It only lights up if the headlights or parking lights are on via the dash board switch. Only other culprit is the bumper light. Turn signals work fine.

While my car was at DMC Midwest a couple of weeks ago, they also replaced the steering column bushing. Is it possible that they snagged something in the process?

[bfloyd]

Second report from the garage ...

Completely removed the new marker lamp socket from the car. No effect. Still blowing the fuse. Unscrewed the turn signal light from the bumper and removed the bulb. Didn't make a difference... still blew another fuse.

Twisted the LED bulb back into the turn signal socket and turned on the hazard lights. All of those work fine. I'm completely stumped.

[sdg3205]

Drop the washer bottle and unplug the molex there. That should eliminate all the front. If you keep blowing fuses its in your harness.

Are you running the factory headlight switch? they are prone to failing.

[bfloyd]

I'll try that next. I need to replace the washer pump while I'm there anyway.

[bfloyd]

Went home from the office today during lunch and did some more troubleshooting on the car. Once again I disconnected the black bulkhead connector to isolate the rear half of the car. Then I went to the front and removed the grill and disconnected the turn signal assembly via the connector right behind the headlights. Next I disconnected the left front fender side marker light using the spade lug terminals I installed back in October when I replaced that socket. Once everything was disconnected, I started the process of plugging everything back in. Replaced the fuse and it held, so that's a good thing. Plugged the rear bulkhead connector back in and the rear of the car lit up like a Christmas tree. Went to the front and reconnected the turn signal lamp. It worked perfect too. Reached over and reconnected the side marker light and POP! Found the culprit.

Now I have to figure out is it a bad socket or the wiring going to the socket.

[DMC5180]

If it's a replacement socket, those are longer than the original assembly and can be a difficult the put in place. The center wire has to bend a sharp 90 degrees and could pinch between the underbody and outer grounded metal socket. The other possibility is the spring inside the socket is somehow bridging between the center wire contact and the outer housing.


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[bfloyd]

It ended up being the center wire of the new replacement socket. Like DMC5180 said, the way that wire was bent coming out of the bottom of the socket, it ended up getting nicked by the outer housing of the socket. I slipped a length of heat shrink tubing over the center wire and snugged it up good and tight. Everything is working again as it should.

Door light switches are next on the list.

Thanks to all of you for your help!

[DMC5180]

[emoji1303]


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