Short circuit, where do I look?

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11-05-2005, 01:11 PM
Hallmark

Short circuit, where do I look?

On one of my '95 525's I'm chasing an electrical gremlin. Here's what I have so far. The left front parking light and left tail light don't come on even though I've replaced the bulbs. Looking at the schematic in the Bentley's I find that these two are on the same pole coming off the switch on the dash. The power goes through two different paths in the LKM and then to the bulbs. the fuse for that pole is blown and when I replace it it blows again as soon as I turn on the switch, so I'm thinking short to ground...right?

I've run each bulb socket through my multi-meter and found that both pins in the sockets show direct connect to ground. Any clue where to look for a short? could a bad connetion inside the LKM cause this?
11-05-2005, 02:08 PM
632 Regal

what about if you disconnect the LKM, then check for shorts?
11-05-2005, 03:11 PM
Hallmark

I'll give it a shot.

Quote:

Originally Posted by 632 Regal

what about if you disconnect the LKM, then check for shorts?

:)
11-05-2005, 04:32 PM
Hallmark

Now who do I trust?

As I was running down the circuits I noticed that the schematic in the Bentley's showed a 10 amp fuse going to this position, but the one that blew was 7.5 amp. The troubling thing is that the fuse list inside the cover of the fuse box shows a 7.5 amp fuse for that position...so, who do I trust?

I tried a 10 amp in that slot just to see (thinking that if it was a short the 10 amp fuse would still blow). Sure enough all the lights came on and stayed on.

Whaddaya think about that?
11-05-2005, 08:41 PM
laguner

Take out the bulbs and see if there is a short in the the circuit by checking resistance from positive to negative in the light socket. Then check the other one. Check the potential from the LKM feeding that circuit and ground. There should be voltage potential if there is no short in the LKM and no short in the socket.
11-06-2005, 10:05 AM
Hallmark

No short at the sockets, but no power either...

so I'm looking in the LKM, correct?
11-06-2005, 10:15 AM
Hallmark

BTW, the 10 amp fuse didn't last long.

Quote:

Originally Posted by Hallmark

so I'm looking in the LKM, correct?

There really is a short somewhere.
11-06-2005, 11:29 AM
Javier

To find a short, you have to split the circuit in ...

as many sections as possible, removing parts and connectors in the circuit. Test each section continuity to ground (should be open circuit if all loads of that section are removed), F5 is a 10A and feed (non canadian) Left Park lights front and rear, interior switch lights and interior lights dimming wheel, lighter light, IHKR lights, GM/CCM (doubt they are the culprits, but), License plate lights, Left markers front and rear.

Considering F5 feeds License plate lights, I would start checking Trunk Hinge harness (search for hinge harness), as it is a known source of short circuits in E34, and F5 circuits are involved there.

Javier
11-06-2005, 01:21 PM
pyro

hey Javier, sounds familiar dosn't it?