help needed-bizarre electrical short on 99 passport.

ttruex · #1 03-12-2009, 06:58 PM

99 passport, been running fine, then monday, bam. dead, nada. I'm getting weird noises from various relays, and all the idiot lights come on very dimly. the dome light is dim, too. I've checked all the ground locations, which seem fine, disconnected the trailer harness, which had no effect. and can't find any blown fuses or obvious bare wires.

If I turn on the Headlights, I get a weird buzzing, with the dim dash lights again. hitting the brake of flashers does the same. I traced the buzzing to the wiper motor, of all things. unplugging it doesn't help. The starter will engage for a second, then off, until I hear a relay cycle in about 5 sec, then it bumps again for a second.

Has anyone come across anything similar? Please don't tell me it's my alternator- it has been running fine for months after I replaced it with a rebuilt NAPA unit.

No warning, no problems until Monday when it died.

any ideas would be helpful at this point- I'm thinking 5 gal of gas and a match is the best solution right now.

fourwd1 · #2 03-12-2009, 09:55 PM

Check the batt voltage with the engine running, should be 14V or more. Use a DMM, not a dash gauge. Re built parts can go bad.

ttruex · #3 03-12-2009, 10:33 PM

voltages are fine- I have 12.8v from the battery as it sits, disconnected. I can't give you a running voltage as it won't start.

voltage hooked up, with all the crazy shit going on, is still 12.5

amigo-2k · #4 03-13-2009, 09:32 AM

Did you try a new or different battery? There could be a bad cell in the battery.

ttruex · #5 03-13-2009, 10:22 AM

This is where it gets interesting- I swapped the battery out my daughter's car just to try that- things came up and ran fine, the car started and ran OK.

So, off for a new battery. Plopped it in, and it fired and ran, no symptoms. Some hours later I thought I woul dtakew it for a spin around the block to make sure things were truly running. I back out of the garage, pull it around, shift into first...and make it halfway down the driveway. Bam. dead. same symptoms again. I trace the weird buzzing sound to the wiper motor, which I unplug. nada, except the annoying buzzing is now gone.

Has anyone ever had any troubles with the alarm and relay control module? Most of the affected systems seem to come through that, from what I read in the schematics.

I'm tearing the steering column down today to see if anything is up with the switches /harness, and will dink around with the various harness connectors to see if I can wiggle something into a diagnosis. I'm also going to patch in another ground cable, just to be sure, although I have examined all the grounds indicated in the wiring schematics.

Given the breadth of affected systems, headlights, brake lights, dash lights and the nature of the fault- repeatable time intervals for relays to reset- I'm thinking it may be semiconductor based, which makes me look at the relay control module or drive mode switch.

This one is truly a bitch to sort out- it seems to affect the whole vehicle. I disconnected the cable leading to the starter, and patched in a link to the main relay box from the POS terminal, and had no change, so I think that rules out a starter winding short.

pharm_rodeo · #6 03-13-2009, 12:50 PM

Sounds like an alternator issue. For some reason you're convinced it's not.

ttruex · #7 03-13-2009, 01:18 PM

Quote:

Originally Posted by pharm_rodeo

Sounds like an alternator issue. For some reason you're convinced it's not.

I replaced the alternator some 4 months ago with a rebuilt denso unit from NAPA- it has been running fine.

I can disconnect the alternator and see if that improves any of the symptoms,
but I doubt an alt problem is affecting a car that has a 2 day old battery and the symptoms I described. It won't even turn over at present, except in blips every 5-10 seconds.

How would an Alt do that?

At this point, I'm pulling every fuse and relay, and disconnecting every device I can in order to isolate the problem. I've eliminated the starter, so I will unhook the alt and see if the weird stuff continues...

amigo-2k · #8 03-13-2009, 02:09 PM

I think that is the missing link... the new to you alt is junk... take it back to napa and ask for a new one...

ttruex · #9 03-13-2009, 02:45 PM

Like I said, I don't see how the alt can cause the types of faults I'm seeing, parked, but I'll yank the leads and see what happens....

ttruex · #10 03-15-2009, 09:55 PM

unhooked the alt today- no difference.

ran a jumper from bat neg to frame. solved.

neg harness looks great, just doesn't conduct electricity.

Cat Fuzz · #11 03-16-2009, 01:22 AM

Quote:

Originally Posted by ttruex

unhooked the alt today- no difference.

ran a jumper from bat neg to frame. solved.

neg harness looks great, just doesn't conduct electricity.

Yep. Sounded like you were over-thinking it a bit. Bad grounds wreak havoc on cars.

ttruex · #12 03-16-2009, 09:22 AM

yeah, over thinking for sure.

The bit I didn't share was the fact that I put a new frame under the vehicle in October. the body is in great shape, it runs great, I just couldn't drive it or sell it with the rear frame rusted through.

Add that to the fact that the car would run sometimes and not others, and I thought I had something worse going on.

Although I was meticulous in assuring proper routing and mounting of the harnesses going back together, it's those recent events that make you over-think, I think

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