Voltage spikes, triggering fault codes

kaellis · Jan 11, 2009

I'm having some intermittent voltage issues. Every once in a while, when the engine is cold and I pass 2500 RPM, when the glow plug relay switches on or off, the lights will flicker badly and various fault codes will be triggered (voltage out of range) and the ABS and brake warning lights will come on. When parked and cold, I can start and watch the dome light, and going up through 2500 RPM it will flash brightly (voltage too high), and on the way back down will dim. Multimeter too slow to catch values. When I then shut the car off and leave the key in the ignition, the LCD displays on the dash (odometer) will go out. Oddly, they will come back on while I have the brake pedal depressed, will go out again when I release. When I remove the key from the ignition, everything back to normal, and the alarm sets. Rarely, after this happens, I will hear repeated clicking from under the dash like a relay tripping a couple times a second.

Note also that I see voltage spikes when I hit the defrost or even turn signals, but it isn't bad enough to trigger fault codes.

I replaced the voltage regulator. Brushes had 8mm left on them, within 1mm of spec. Didn't help though. I removed and cleaned the negative battery cable. No help. Relay 109 has been replaced. I'm thinking the LCD and brake pedal weirdness is just a result of the voltage drop.

Any ideas here? In absence of any suggestions for diagnosing, I'm thinking replace the glow plug relay. The problem is getting progressively worse.

2000 Jetta TDI, 135k miles.

whitedog · Jan 11, 2009

You were on the right track with the ground wire. You probably just need to clean the rest of the grounds. Did you Clean the groundunder the battery tray and all connections on the block? I'm unsure of where all of the grounds points are for your car, but searching this site should yield more ground points.

kaellis · Jan 12, 2009

ground points

Thanks for the advice. I only cleaned the ground connections for the negative battery cable (one under the battery tray, and one at the engine block). I'll hunt down grounds for other components and clean them as well.

ubercam · Jan 12, 2009

I'm not sure whether this is related or not, but it seems close enough. I did a search on here and Vortex and this is the closest description I could find.

I was driving the 2002 Jetta TDI yesterday, and when I first started the engine, the ABS warning light came on, the clock reset to 0:00 and the trip odometer reset to 0km. After a couple seconds it stopped beeping and calmed down and went back to normal, all the warnings turned off. I tested the ABS right away (not hard, the roads are skating rinks out here) and it worked perfect. On the way home, I thought my eyes were playing tricks on me, because I would see the dash background lighting flickering randomly (gauges, radio, heat/fan control background lighting). The radio sounded fine, the car ran fine. I tried adjusting the dimmer switch, but it didn't stop the flickering. I'm not sure whether the interior lights would have flickered since they weren't on during the drive.

I plugged in my fake $20 vag-com and it found no stored faults related to voltage (it did find a couple random unrelated ones I already knew about), but it can't talk to the ABS module due to "too many communication errors" which I understand is normal for el-cheapo adapters. I'd try reading the modules when the car's running, but I'm afraid that if it's voltage spikes that it might potentially fry my cable and/or laptop.

I will check the battery terminals when I get home. I doubt the alternator has ever been looked at or thought of until now. It's got around 205k-210k km on the clock.

weedeater · Jan 12, 2009

There is a ground point behind the instr cluster and under the center console. Also by your left foot.

jamesandruth · Mar 5, 2013

A fix that worked for a while

kaellis said:
I'm having some intermittent voltage issues. Every once in a while, when the engine is cold and I pass 2500 RPM, when the glow plug relay switches on or off, the lights will flicker badly and various fault codes will be triggered (voltage out of range) and the ABS and brake warning lights will come on. When parked and cold, I can start and watch the dome light, and going up through 2500 RPM it will flash brightly (voltage too high), and on the way back down will dim. Multimeter too slow to catch values. When I then shut the car off and leave the key in the ignition, the LCD displays on the dash (odometer) will go out. Oddly, they will come back on while I have the brake pedal depressed, will go out again when I release. When I remove the key from the ignition, everything back to normal, and the alarm sets. Rarely, after this happens, I will hear repeated clicking from under the dash like a relay tripping a couple times a second.
Note also that I see voltage spikes when I hit the defrost or even turn signals, but it isn't bad enough to trigger fault codes.
I replaced the voltage regulator. Brushes had 8mm left on them, within 1mm of spec. Didn't help though. I removed and cleaned the negative battery cable. No help. Relay 109 has been replaced. I'm thinking the LCD and brake pedal weirdness is just a result of the voltage drop.
Any ideas here? In absence of any suggestions for diagnosing, I'm thinking replace the glow plug relay. The problem is getting progressively worse.
2000 Jetta TDI, 135k miles.

I am having the same troubles. Again. Let me tell you how I've solved it in the past, TWICE, and see if the TDI gurus can come up with a permanent fix.
Note: this is not just a tiny, annoying flicker. This is major electrical craziness, which cooked a radio once.
First: This is most likely caused by the draw of the glow plugs as they cycle with a cold engine. Proof: I unplugged the GP wires and problem goes away. This works fine in the summer, not so much in the winter.
Stumped, I took my 2003 TDI Golf to an excellent TDI guy in Minneapolis (Jeppesen) and he fixed up my grounding points, with little effect. Then, on a hunch, he replaced the fuse block (1J0937617D, OEM) on top of the battery. Problem fixed. For a while. A year or so later, the problem came back. Then I replaced the fuse block with a cheapo Chinese part of ebay. Problem fixed for a month or two. Now the problem is back.
The fuse box I took off (#2 OEM) seemed to be in good condition: no melting or obvious opens. Nonetheless, the car ran great on the cheap part (#3 cheapo)
Any idea what is the root cause, and why replacing the part fixes it for a while?

wmgeorge · Mar 6, 2013

The fuse box I took off (#2 OEM) seemed to be in good condition: no melting or obvious opens. Nonetheless, the car ran great on the cheap part (#3 cheapo)
Any idea what is the root cause, and why replacing the part fixes it for a while?

What about the wire connection or crimped terminal to the wire? As a electrician I can tell you weird things can happen, things you will scratch you head and say, I've never seen that before!

You are moving the wires around when replacing those parts and that temporarily fixes the problem. Another thought, are you 100% sure the battery cable connectors are good and a far, far out one... battery internally the connection to the post is faulty.

Voltage spikes, triggering fault codes

kaellis

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whitedog

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kaellis

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ubercam

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weedeater

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jamesandruth

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wmgeorge

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