Unique electrical problem, long, for expierienced users

[turbo2086]

I searched through the forums for a similar problem, but nothing like this:

This started out of the blue one day.

INFO/FACTS:

There are three main wires that are attached to the positive terminal. One that has three main fuses, one that goes to the alternator fuse, and one for the starter. I'm concerned with the one that goes to the alternator fuse. From the alternator fuse it gets split to 6 other sub fuses.

With just the ground connected to the battery, it reads 12.6 volts. I will only connect that one positive wire (coming from the alternator fuse) and it will jump down to 8.9ish volts. The positive termnial also gets very warm. I traced it from there, using the method on this site in the write up section, and a copy of the chysler service manual.

I traced through the sub fuse 6 (says bat on top cover), to multi fuse 19 ( very bottom fuse in the fuse box underneathe the dash). So if I disconnect that fuse, then check the battery, it reads 12 volts, reconnect and its back down to 8 or 9 volts.

According to the manual that fuse controls the doom light, door ajar warning light, foot light, ignition key illumination light, luggage compartment light, MPI control unit (ecu battery back up), radio, automatic seat belt control unit, and door lock control unit.

This is where I'm lost. I've unplugged the seat belt control unit, and door lock control unit, but doesn't seem to do anything. I figured if it were the lights, they would blow out.

I'm looking for ideas, cause what boggles me is that I'm not blowing fuses, or tripping relays, but the very warm terminal and the voltometer say other wise. I haven't been able to use my car for a week, so if any ideas will be appreciated. Thanks.

 

[Defiant]

Sounds like a dead battery, and a bad ground.

 

[luv2rallye]

...According to the manual that fuse controls the doom light, door ajar warning light, foot light, ignition key illumination light, luggage compartment light, MPI control unit (ecu battery back up), radio, automatic seat belt control unit, and door lock control unit.

Check all grounds first. If all ok somewhere in the above wiring there is a partial short. Replace the fuse with a small 12V light bulb so you can visually see the current draw. Then disconnect EVERYTHING (including all lights/bulbs) on that wiring harness until the light goes out (last one has short).

If it's still on, the short is in the wiring. Then wiggle that harness to see if you can make the light go out. Also look up/down that wiring harness to see if there's anything suspicious (eg. anything new added or wires that obviously touch each other - also check behind that fusebox for wires touching). If still can't locate it you may have to disconnect battery and connect a digital ohmmeter (multimeter) from the load side of that fuse to ground - note reading. Then measure on that wire at the various connectors you unplugged to find a lesser reading which means you're getting closer to the short and it's on that wire. When you finally locate the wire with the short follow it to see where it goes. You can also pierce thru the wires insulation with a safety pin to get at the wire at different places along it for identification or measuring. Shorts in wiring are rare - it's almost always in the things the wires connect to. And in cases where it is the wiring, it's almost always at the connectors so examine those before you start probing with an ohmmeter to save time. Good luck.

 

[BoostedTalonTS]

I would agree: Start with an ohmmeter and go from there... It will end up save time. Good luck.

Usually, these rather low current shorts are sometimes the hardest to locate, as you have norrowed the problem to the main and sub-power systems, I would look into the radio area... Being that your problem is not a significant short (not enough of a short to blow fuses), I would suspect a simple mistake in the radio grounding can cause this low current short. Specifically, hooking up the car's dimmer and/or illumination wires to the radio's ground wire and/or chassis ground has been a known curprit to plauge every green installer that has ever installed a an aftermarket radio in a 1g DSM. -Armed with your meter, I'd start testing the radio wiring first. If not, then just unplug any other microprocessor-controlled electronic device on that system -as illustrated here:

Quote:
Originally Posted by turbo2086
...According to the manual that fuse controls the doom light, door ajar warning light, foot light, ignition key illumination light, luggage compartment light, MPI control unit (ecu battery back up), radio, automatic seat belt control unit, and door lock control unit.