VW electrical weirdness I can't figure out: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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March 4, 2011 10:12 p.m. Treb Reader

I grew up in Fiats and Alfas, and my first car was an MG.

But VW electrics are screwy.

200,000 mile VW Jetta MKIII. 1995.

Occasionally -- like every 500 miles or so -- I'll hit a bump and the engine will cut out for a small fraction of a second. It won't die completely, but it will cut out.

Problem that you wouldn't think would be related: the radio is dying, and occasionally needs the fuse pulled out of the back and put back in before it will power up.

So the other day, the radio problem cropped up, and I pulled the fuse from the back of the radio. Put it back in and the engine cut out. Hmmm. Radio still not working. Pushed on the fuse -- engine cuts again. Still no radio.

Pull the radio entirely. Hitting bumps still occasionally causes the engine to cut out.

So, what the heck?

Matt
March 4, 2011 10:23 p.m. Ian F SuperDork

Sounds like a possible bad ground. Or a short, but I think a ground is more likely. Finding it, however, will be a task I don't envy.
March 4, 2011 10:28 p.m. benzbaron HalfDork

I had a battery terminal do this on my pickup truck. I'd go over a bump and all the electrics would die a second, then it would turn back on. It was a battery terminal that was worn out. I replaced the terminal and now all is good. If it was the same issue as my car I'd bet the battery cable gets loose and starves the radio for power. I think accessories die in a certain order of importance.
March 4, 2011 10:31 p.m. Treb Reader

Hm.

While I like the idea of a battery terminal, I fear the bad-ground-somewhere.

But hey, having a simple thing to try first is nice.
March 4, 2011 10:36 p.m. ditchdigger HalfDork

I had a similar problem and it went away with a new ignition switch. Not the whole tumbler, just the cheap electrical portion that screws in on the back side. They are a known problem area on these cars
March 4, 2011 11:14 p.m. peter Reader

What about the fuse box itself? Wonder if there's a structural/electrical defect there where maybe the contacts for a couple of fuses, eg ECU and radio, are loose and able to disconnect when you hit a bump?
March 5, 2011 2:14 p.m. carzan HalfDork

My first thought was bad ground, too, but if you can monkey with the radio and duplicate the symptom, I gotta believe that is a clue.

I'm assuming there is a fuse for the radio in the fusebox. Can you pull it without it disabling something else vital on the same circuit? (like brake lights, etc.). Drive it without that fuse, if possible and see what happens.
March 5, 2011 7:24 p.m. carguy123 SuperDork

My experience with VWs says this isn't electrical weirdness, it's VW normalness.

Had the same issue in 2 VWs and no one could find or fix it. It got worse. Every VW house in the metroplex looked at it at least once along with every electrical guru and

I've personally watch 2 VWs spontaneously combust and burn to the ground. One while it was driving on the Fwy, one while it was sitting in a driveway.

That didn't even touch the windows that the supports broke and fell down all the time along with the power window motors burning out all the time. Oh yeah, the ac worked when it wanted to.
March 5, 2011 7:36 p.m. TRoglodyte Reader

VW = Very Weird
March 6, 2011 7:38 p.m. Treb Reader

Thanks for all the thoughts on this one.

There is a fuse I can pull -- just the radio, cigarette lighter, and the electric trunk release. I'll try that & see what happens.

Had an audi that had all kinds of weird electrical goings-on; replaced the electrical portion of the ign. switch and it all got better. So that's a real possibility.

And carguy, TRoglodyte... yeah, you said it. Thanks, all. Matt
March 7, 2011 8:40 a.m. NGTD HalfDork

Ian F wrote:

Sounds like a possible bad ground. Or a short, but I think a ground is more likely. Finding it, however, will be a task I don't envy.

^^^ This - VW's are infamous for grounds going bad. Check all your ground straps. They rust away or develop high resistance over time.
March 7, 2011 8:52 a.m. vwcorvette Reader

IGNITION SWITCH! Replace the lock cylinder and electrical portion. My guess is the key turns kinds funky and doesn't always return all the way to the on position from start. Replace more than my fair share as a dealer tech.
March 7, 2011 9:05 a.m. ditchdigger HalfDork

Seriously. The ignition switch.

http://www.mjmautohaus.com/catalog/product_info.php?info=Meyle_6N0905865MY_Ignitio...

It is under $10 shipped and is notorious in that generation VW. On one of mine the headlights would flicker, the instrument cluster would cut out and there was a mid throttle bog that I could never figure out. I replaced the cheap switch hoping to fix the cluster and it cured everything else.
March 7, 2011 11:30 a.m. Treb Reader

Switch and ground strap tonight. Will report.

Matt
March 7, 2011 2:33 p.m. Paul_VR6 HalfDork

Little late but I'll third/fourth/millionth ignition switch.
March 7, 2011 10:54 p.m. Treb Reader

Just did the ignition switch. We'll see how it goes. Matt
March 8, 2011 7:35 a.m. Treb Reader

New ign. switch, fuse for radio etc. still in; one ignition cut-out on the way to work this morning. Can't tell if there are other beneficial effects of the new switch -- turning the key is stiffer, but see no other effects at this point.

I didn't get to the battery ground strap last night; I'm going to replace that as the first stop in the attempt to find a bad ground.

Matt