dash lights blinking on and off

My son just bought a 2001 tdi-(just like mine) and is having trouble with the dash lights blinking on and off. I've always done the maint. on my jetta but don't know much about the electicals. Could anyone give me a starting point? Typical trouble shooting???
Thanks Mayn

Please post more detail info what is meant by dash lights blinking on and off ?
Does it appear like a problem localized to maybe the dimmer switch, where just the gauge lights and back lights are doing odd things ?
Is the entire dash and radio going on and off ?
Something else altogether ?
=
I will share one thing from my own past experience, as it can throw people a curve ball on diagnosis. Not suggesting at this point that this would be the issue you're encountering, but something to keep in mind: Here are two pieces of info:
[a] when an alternator fails, it can fail in one of two ways: it can fail so it just doesn't charge at all any more. That is, it doesn't elevate the system voltage at all, so just the battery is what supplies electricity to the car. This is, I think, the most commonly thought failure mode of the alternator. But there is a different type of failure that can also happen- that would be where the Voltage regulator (which resides inside the alternator on most cars these days, including yours.) fails in the shorted condition. When this happens, the alternator can bring the system Voltage way above the nominal 14 Volts or so that is normal. A failed (shorted) regulator in the alternator can allow the system Voltage to get well above 17V, 18V. That would typically happen when the engine was sped up above idle.

I learned first-hand some years ago, these cars seem to have some protection built into them, that if the system detects Voltage too high, something trips and shuts off a bunch of things but not everything. I noticed my instrument cluster went dark, I think the radio also went off. Some things stayed on. The engine kept running. I think the headlights stayed on (but not sure 100%).

So anyway, if you find that things all seem OK when the engine is idling, but things start to shut off when the engine is revved some amount above idle, the cause could be a failed alternator. That can be measured by placing a digital Voltmeter across the battery terminals and watching what happens with the engine off, then with the engine running and revved to 2000 RPM or so. Engine off should be 12V to 12.8V or so (if the car was just shut off, it will be on the high side, then often gradually down toward 12V). Engine running, should be at least 13.5V, to about 14.5V typically. Varies with temperature, but that's ballpark. Engine revved to 2000, Voltage should remain fairly steady, within a few tenths. BTW if you do find the Voltage is going way up when revved, I recommend don't drive the car- get the alternator replaced. Although some things shut off for protection, not everything does. My battery got cooked just on a short drive home- The alternator was what failed, but my continued short drive home resulted also in a cooked battery. That was a few years ago.

Again the above is shared because it can be a "Gotcha" in diagnosis- seems unusual. Depending on what the further details of your symptom are, this may have nothing to do with your particular situation.

Wish you all the best !!

Thanks Corsair. I talked with my son and here are some more details on what the car has been acting like.

The instrument lights flicker and the headlights seem to do the same, but not as noticeably. (He's says that the headlights don't actually go off, its more that they seem to dim very slightly.) He tried dimming the dash lights and he says that it seemed to make it better. He said that there was a clicking noise under the dash, nothing that continues on. It was a "click click" then nothing else while driving. The same thing happened again on the next trip. The radio lights don't seem to be affected by any of this. I should also mention that it doesn't seem to matter what the rpm's are. Idleing or driving the problem persists.

Fuse #22 and 23 (if I recall correctly-anyways there are two of them) are listed for the side/tail/marker lights left and right side. If either fuse, or related wiring, is having an issue it will affect the instrument cluster lighting.
VW seem to have issues with the ground connections, especially those under the battery box. Check/clean those and check the fuse holder connections also-especially for the side marker lights (#22/23?). My '03 had the plugged/disconnected sunroof drains and water would leak right down thru the fuse panel. Corrosion waiting to happen.

Maybe the dimmer switch could be the culprit.

I would check, clean and tighten the battery terminals and check/clean the grounds and positive connections under the hood.

Check the fuse holder on top of the battery for burnt, melting or loose connections. Vapors from the battery can cause corrosion to the fuses and connections leading to this problem.

Hello,

I am the above mentioned "son" of Mayn. So I have taken the advise and checked the #22 and #23 fuses, they are fine. The battery connections are tight and clean. There are no burnt or corroded connections. The only thing that I haven't checked is the dimmer dial. Correct me if I'm wrong, but the dimmer dial is just a variable resistor. This being said I should be able to disconnect the dial and place and ohm meter to it, finding out what the maximum resistance is. Then if I jumper the dial with a resistor, matching the dials maximum resistance, in series it should make the instrument lights always glow bright. If the problem goes away then I have determind the problem, correct?

I don't know if any of this makes sense or if I'm over thinking all of this. Any feedback is appriciated.

Ok, so I pulled the dimmer dial out and unplugged it. Then I turned on the headlights and the dash lights shine bright and headlights come on, but all the other dash lights are off.(Radio, hazards, locks, etc.) It seems to me that if the problem was the dimmer then wouldn't all of my dash lights, including the radio, hazards, etc. be flickering too?

Something else that I have a question about is that when I open the drivers side door the interior lights don't come on. Yes, I have the switch in the correct position. If I open any other door all of the lights come on as they should. In the fuse box on the drivers side dash the dome light fuse #14 is missing. What is this fuse rating suppose to be? And could this missing fuse cause only the drivers side door to be effected?

Girlfriend called and said the 2001 beetle is doing this with the dash lights. Did anyone solve this? My best guess is the voltage regulator but I can't check it till tomorrow.

In the 03, the battery light would momentarily come on. the headlights would flicker and the belt tensioner would bounce around. It turned out to be bad alternator bearings . I would get <14 volts at the battery when checked with a DVM.

JB05 said:

Maybe the dimmer switch could be the culprit.

Click to expand...

Turns out it is just the illumination. If you roll the dimmer then the lights flicker so it seems the guilty party. Now to find one for sale.