interior light short

[ccclarke]

Pulling bulbs might not be the best course of action, as bulbs (and LEDs) don't generally short. They open. A decent multi-meter need not be expensive and they're great for all kinds of projects and repairs. A meter is to electrical guys what a hammer is to carpenters or an IED is to terrorists. I highly recommend obtaining one and having someone teach you how to use it; it isn't difficult to use once someone shows you how. Whoops, just fell off my soapbox! Let's get back to the problem at hand.

Here's one (of many) routes you can take, based on the test equipment you currently are using. Connect your lighted tester, and verify the short is present. Find the brightest flashlight you can get your hands on and get ready to use the second best piece of test equipment in your arsenal: The good old, MARK 1/Mod 1 eyeball. Take detailed notes as you do perform this procedure to prevent repetition and find your way back if the symptoms change while you progress toward finding the fault.
Open the doors, and cycle the switches that activate the interior lights. Shake the harness that exits the doors and enters the car near the hinges. If you can remove the door panels, go ahead. What we're looking for is chaffing of a wiring harness on a repetitively (doors opening and closing regularly) moving surface. If you can get in the door panels, slowly and carefully inspect the harnesses for any signs of wear and tear, especially where the harness contacts any metal surface as it routes through the vehicle. A short can be impossibly small physically, but still able to cause enough problems to ensure you pull most of your hair out while troubleshooting, so use that super-bright light you've got to eyeball the harnesses while rolling them around to look at all sides.
This is basically the procedure for the entire lighting system you need to perform. Trunk lids (another moving surface with a harness to chaff) are another culprit. Go slow and eliminate as much as possible, then report your findings. Look for bent leads on switch contacts, broken/cut wires, etc. If the trouble light goes out while you're shaking harni (plural for harnessesessesss in geek-speak) you're there buddy!

Don't despair, there are many ways to eat this elephant, but the basic tactic is always: One bite at a time! Go man Go!!!
CC

[Eldyfig]

CC, you are right about pulling bulbs. That wouldn't solve anything. There will still be 12v going to the socket. What about short finders? Have you ever used one and if so, are they any good?

[johndfw]

ccc .......Thanks
You have inspired me to go on! I may go after it tonight after work.

I'll let you know how it goes.

[ccclarke]

To answer your question, I don't have a lighted circuit continuity tester. I'm a multi-meter kind of guy with 25 years' exp with electronics. I've spent more hours than I care to remember chasing elusive problems that make you want to seek therapy by the time the fault is isolated --especially with shorts and opens, while working on a wide variety of systems, from submarine weapons systems to spacecraft. A continuity tester will work for this problem, but a multimeter gives you more info, like resistance to ground. Any tool is better than no tool when you're working on a problem like this!

[Eldyfig]

Do you have any hair? This stuff would make you want to pull it out sometimes.

[johndfw]

Eldy
I still have some.......not much, and want to keep it. I need to save as much as possible........., my kids are entering their teens.

Later

[Eldyfig]

That would make it come out. My oldest is 9 so I still have a little time to hold on to mine.

Good luck with the short. Let us know how it goes.

[johndfw]

I put a fuse in the slot, and the lights came on for about 5 seconds. I noticed some light flickering at the dome light just before the fuse poped. I guess its the dome light.....it has two seperate lights and some kind of hatch think with a spring loaded door. There is an electrical connector in there. I think I'm going to fiddle around with that tonight. I dont know what plugs into that hatch.

Later

[ccclarke]

Ahhhh. . . some more info. The mystery deepens. . . I don't want to derail your thought train, but the flickering dome light might be a symptom and not the cause. If you placed a new fuse in the circuit and you had partial operation for five seconds, that is a good clue. A hard short would usually blow instantly. (I'm using generally and usually becuase there are no hard and fast rules when troubleshooting. One must always keep an open mind to avoid tunnel vision.) A slow-blo fuse might work for a VERY short time. You might try this, just 'cause it's quick: Open all doors and the trunk and install a new fuse. (Just in case a chaffed harness is contacting the frame.) Keep us posted!

CCC

[johndfw]

ccc.......I did it last night. Opened all doors and trunk, and put in a fuse. All lights worked. As I looked around I noticed one of the dome lights had gone out, so I pushed the button. It came on. Now all lights work. I jiggled the harnesses,and open and closed doors ect....All still working. I'm glad they are working, but a little perplexed about the hole thing.


You seem to be a real guru of this black art. Thanks much.

Later

[Eldyfig]

I don't understand what was causing the fuse to blow. How is the problem solved? Was it the button? What button is this?

Perplexing to say the least.

[johndfw]

Eldy

I'm not sure either. Now my door locks also work, same fuse.
The button is one of two just above the rear view mirror (map lights I think). Right now I'm not toutching them.
Does your car have the same set up? That little hatch door by those lights .......Whats it for?

Later

[Eldyfig]

I dont have lights up there, but I do have a little hatch...for a garage door opener.

[ccclarke]

Nice to hear you've made substancial progress John. I'm not convinced the problem is resolved though . . . just dormant. I don't mean to rain on your parade, It's just that I've seen phantom faults dissapear, only to show up when I least need or expect them. So . . . with that said, I would zero in on your door/trunk harni and give them a very slow, methodical visual inspection, paying close attention for a small, black speck (could be as small as a pencil lead) on the vehicle's frame in the vicinity of where the harnesses come closest to the frame when the particular door is closed. Look for a small, black or whitish discoloration on the harnesses, or tiny pinch marks in the insulation. Use the brightest light available to you. There's also the other side of the argument that has credence: "If it works, don't mess with it." The choice is of course, yours. Good luck with this and don't hesitate to return to this forum for any help or advice from the excellent members who frequent these areas.

Cheers and Happy Motoring! CC

[johndfw]

cc.......
Thanks for the thoughts. I'm going to continue to tinker with it, but I'm still not sure about whats going on. All my lights are working, and door locks. Its great.

Thanks