Cadillac Owners Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
201 Posts
Discussion Starter #1
Hey folks

Anyone know how to track down a short at the interior light cir.?
I replaced the fuse and it blew once I got going.

Any help would be appreciated
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
What car?

Have you recently done any work or experienced something that might have caused a short?

I had a short recently caused by the wind catching my trunk lid after I opened it from inside the vehicle. As the lid came up, the wind forced it up harder. I found two wires shorted in the harness from the trunk lid to the trunk...two months later.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #3
Hey Eldyfig

Its an 87 brougham (307). I bought the car with the interior lights not working. I replaced the burned fuse and they worked. When I got back in the car 10 min. later, they were back out. I think I might have some loose wires behined the dash, Im not sure where to start
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
Factory stereo or aftermarket? The previous owner may have dove work on it somewhere and may have pinched a wire.
 

·
Registered
'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
Joined
·
2,518 Posts
Here's a little trick I've used countless times to find shorts in fused circuits:

Since the fuse blows and you know you have a dead short, start by pulling the fuse and connect one side of the ohmeter to the shorted side (not power) of the fused circuit. Clip the other lead to a good ground and you should get 0 ohms or very low resistance (this verifies your shorted condition without having to use a fuse). If the ohmeter has a tone to verify ) ohms, start wiggling your wires in the lighting circuits, documenting everything as you progress. For interior lighting shorts, look carefully around the door switches and wiring of the harness where it goes between the door and car for signs of chaffing. Cycle the doors while watching the ohmeter, etc. Keep at it until you isolate the short. The ohmeter is a great tool, but your eyes may find it just as easily! Good luck!
CC
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
I like that. It sounds very useful. I hope I remember it the next time I have a short. It would also give me an excuse to upgrade my current multimeter to a better one with a tone alert.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #8
Hey folks
I pulled the radio..........there has been some monkey business. It looks as though the original radio has been put back in. A factory connector has been spliced in to hook up to the radio. Also ......the radio has a lot of places for plugs ect.....It seems like way to many conections go through the radio.

Any thoughts would be helpful

thanks
 

·
Registered
'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
Joined
·
2,518 Posts
Let's stick with the original fault which may or may not have anything to do with a previous radio replacement. With the radio disconnected, does the lighting problem go away?
 

·
Registered
'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
Joined
·
2,518 Posts
Okay, let's start with the basics; this problem HAS to be driving (no pun intended) you nuts already. . . When you pop in a new fuse, idoes it blow instantly? If not, does activating some portion of the lighting circuit cause the fuse to blow? --Headlights, door switch closing, etc. If the fuse blows instantly, if you place a multi-meter on the shorted side (not the power side, or you get to buy new fuses for your multi-meter!) of the fuse holder (--just to play it safe and avoid measuring the wrong test point, make sure the fuse is removed, too!) what kind of resistance reading are you seeing? --This is to check for a dead short (0 ohms) as opposed to low resistance. Okay. . . it's time to play twenty quetions now: What work has been done on the vehicle lately? When did you first notice the problem? Was it intermittent, or did it occur and never go away? If it did appear and take up residence, what were you doing when you first noticed it? Report back and we'll continue!

--No problems, just solutions awaiting discovery! CC
 

·
Registered
Joined
·
201 Posts
Discussion Starter #12
Thanks ccc

The car had the problem when I bought it last week. The first thing I did was check the fuse (body fuse). It was blown, so I replaced it. All the lights worked. I went inside to get somthing and came back out to go home,and noticed the lights didnt work again. The drivers door was opened when I istalled the fuse, and I closed it when I went inside. (all in about 5 min.)
Now the fuse blows as soon as I install it. I havent done anything on that circuit.
I made a test light that I put in place of the fuse. It lights up. I was told when I unplug the shorted component that the light would go out, but thats a lot of lights to check.

Later
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
I have one of those fuse test lights...plugs right into the fuse holder and has a small bulb on top of it. They work in helping find a short. It has came in handy.

Do you have a multimeter like cc mentioned?
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
I don't have one, but I have seen devices at the tool store and my father mentioned he has one...a short finder. CC, have you used one of these?

I think you should start pulling bulbs.
 

·
Registered
'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
Joined
·
2,518 Posts
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
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
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?
 

·
Registered
Joined
·
201 Posts
Discussion Starter #18
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.
 

·
Registered
'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
Joined
·
2,518 Posts
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!
 
1 - 20 of 30 Posts
Top