What did you do to your MKIV today?

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
I evidently chased non-existent electrical gremlins for a half-hour:
Leaving work, my headlights wouldn't come on. It was getting dark fast and figured I needed something to light my way: flipped to high-beams. They blipped on and went dark. ***! Figured I had some screwed up electrical problem. Had a co-worker lead me home, driving with flashers.
Pulled into the garage and started digging into fuses, switches, etc., finding nothing wrong. Checked voltage at the bulbs (Something I should have done to begin with) and measured battery voltage. Checked bulb resistance.... open-circuit. On Every Single Bulb!!
Through some mystical act of Volkswagen, all four headlight bulbs popped at the same time!
To add to the frustration, I drove past 4 different auto parts stores on my way home without thinking that I would need a bulb... Let alone FOUR!
Got a ride to the nearest Autozone, swapped the bulbs, and everything works again...

Easily the most frustrating/annoying/dumb-founding "repair" I have ever done.
Have you checked your alternator? I've seen several trucks come through the shop that kept blowing headlight bulbs and they all had high ripple current from the alternator. Though, it could be possible for all of them to blow at once (random often comes in groups) but I'd probably recommend checking for ripple (stray AC voltage being put out by the alternator, caused by failing diodes) you can get it checked at an auto parts store, or best would be to have someone with a oscilloscope check it, since that's even more accurate. (Oscilloscope is my preferred method, but I'll often use a handheld alternator tester on the car for speed sake.)
 

CableJockey

Veteran Member
Joined
Apr 20, 2019
Location
South Dakota
TDI
2002 Golf GLS
Have you checked your alternator? I've seen several trucks come through the shop that kept blowing headlight bulbs and they all had high ripple current from the alternator. Though, it could be possible for all of them to blow at once (random often comes in groups) but I'd probably recommend checking for ripple (stray AC voltage being put out by the alternator, caused by failing diodes) you can get it checked at an auto parts store, or best would be to have someone with a oscilloscope check it, since that's even more accurate. (Oscilloscope is my preferred method, but I'll often use a handheld alternator tester on the car for speed sake.)
I've been suspecting my alternator for a while, but haven't been able to definitively declared it bad. AC ripple is non-existent using a multimeter. Current output still meets expected: 115A under carbon-pile load tester. Charge voltage steady at 14.4v (Sagging to ~13v during carbon-pile test) New clutch/pulley.
Primary issue I keep seeing is a shift in headlight brightness if I goose the throttle: brightens slightly, then dims, before settling back to 'normal'.
I haven't had the motivation to drag the oscilloscope from the basement, but it may be a good idea....
The dimming has occurred since I got the car some 2 years ago, and this is the first time I've had a headlight go out. So while I agree that it may be related, it doesn't seem likely.
Yet the chances of losing all four is so incredibly unlikely, there has to be a cause.... Definitely a head-scratcher.
 

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
Through some mystical act of Volkswagen, all four headlight bulbs popped at the same time!
To add to the frustration, I drove past 4 different auto parts stores on my way home without thinking that I would need a bulb... Let alone FOUR!
Got a ride to the nearest Autozone, swapped the bulbs, and everything works again...

Easily the most frustrating/annoying/dumb-founding "repair" I have ever done.
Go buy a lottery ticket - quick! The odds of all 4 going at once is low.
 

rwthomas1

Veteran Member
Joined
Oct 16, 2002
Location
Wakefield, RI
TDI
'03 Jetta
I've been suspecting my alternator for a while, but haven't been able to definitively declared it bad. AC ripple is non-existent using a multimeter. Current output still meets expected: 115A under carbon-pile load tester. Charge voltage steady at 14.4v (Sagging to ~13v during carbon-pile test) New clutch/pulley.
Primary issue I keep seeing is a shift in headlight brightness if I goose the throttle: brightens slightly, then dims, before settling back to 'normal'.
I haven't had the motivation to drag the oscilloscope from the basement, but it may be a good idea....
The dimming has occurred since I got the car some 2 years ago, and this is the first time I've had a headlight go out. So while I agree that it may be related, it doesn't seem likely.
Yet the chances of losing all four is so incredibly unlikely, there has to be a cause.... Definitely a head-scratcher.
Sounds like voltage regulator or associated hardware is malfunctioning intermittently. I'd replace that alternator before it frys something more expensive like the computer...

RT
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
I've been suspecting my alternator for a while, but haven't been able to definitively declared it bad. AC ripple is non-existent using a multimeter. Current output still meets expected: 115A under carbon-pile load tester. Charge voltage steady at 14.4v (Sagging to ~13v during carbon-pile test) New clutch/pulley.
Primary issue I keep seeing is a shift in headlight brightness if I goose the throttle: brightens slightly, then dims, before settling back to 'normal'.
I haven't had the motivation to drag the oscilloscope from the basement, but it may be a good idea....
The dimming has occurred since I got the car some 2 years ago, and this is the first time I've had a headlight go out. So while I agree that it may be related, it doesn't seem likely.
Yet the chances of losing all four is so incredibly unlikely, there has to be a cause.... Definitely a head-scratcher.
Is it an oem alternator, or aftermarket?
It does sound like you got problems with it.
You mention that there was no ripple current when you used a multimeter? It's normal to have a little bit (max .25 vac) you'll need to put it on millivolts AC, not 12 volts...
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
I've been suspecting my alternator for a while, but haven't been able to definitively declared it bad. AC ripple is non-existent using a multimeter. Current output still meets expected: 115A under carbon-pile load tester. Charge voltage steady at 14.4v (Sagging to ~13v during carbon-pile test) New clutch/pulley.
Primary issue I keep seeing is a shift in headlight brightness if I goose the throttle: brightens slightly, then dims, before settling back to 'normal'.
I haven't had the motivation to drag the oscilloscope from the basement, but it may be a good idea....
The dimming has occurred since I got the car some 2 years ago, and this is the first time I've had a headlight go out. So while I agree that it may be related, it doesn't seem likely.
Yet the chances of losing all four is so incredibly unlikely, there has to be a cause.... Definitely a head-scratcher.
I'd for sure recommend pulling the oscilloscope out. You can find charts with what the waveform is supposed to look like online. It shouldn't have spikes in voltage at all, and AC current should be below 0.3 volts ac
 

hey_allen

Veteran Member
Joined
Nov 25, 2006
Location
Altus, OK
TDI
2000 Jetta TDI
I second the recommendation to use an oscilloscope.
I had an alternator rectifier bridge fail on my car (an older MB, but still the same technology) and it just wouldn't charge, even though the voltages looked correct as far as the volt meter showed.

A normal waveform should have shown a steady fine ripple, without the deep crevasse 1/6th of the time in this case.

 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
I second the recommendation to use an oscilloscope.
I had an alternator rectifier bridge fail on my car (an older MB, but still the same technology) and it just wouldn't charge, even though the voltages looked correct as far as the volt meter showed.

A normal waveform should have shown a steady fine ripple, without the deep crevasse 1/6th of the time in this case.

This article explains it fairly well.
 

Nero Morg

Top Post Dawg
Joined
Oct 19, 2017
Location
OR
TDI
2014 A6 TDI, 2001 Jetta TDI, 2014 Passat TDI
Finally got around to installing my drivers door lock actuator. For the past month I've had to manually lock and unlock my door. I also had to take out the hatch latch and repair it, the microswitch got some moisture in it, and kept setting off my car alarm. That was fun....
 

rwthomas1

Veteran Member
Joined
Oct 16, 2002
Location
Wakefield, RI
TDI
'03 Jetta
How many people own an oscilloscope? They look kinda pricey, well, there are cheap Chinesium options, but I wouldn't know a good one from a bad one. What else are they good for? RT
 

hey_allen

Veteran Member
Joined
Nov 25, 2006
Location
Altus, OK
TDI
2000 Jetta TDI
How many people own an oscilloscope? They look kinda pricey, well, there are cheap Chinesium options, but I wouldn't know a good one from a bad one. What else are they good for? RT
I bought mine for $20 used, but even something like the cheap DSO-nano would work for this sort of testing.

As to how many people have one, that is entirely dependant on the interests and hobbies of your group of friends and acquaintances.

I'm sure I don't get the most out of the one I have, but do drag it out occasionally to test something that a meter isn't far enough to display, among other things.
 

Nero Morg

Top Post Dawg
Joined
Oct 19, 2017
Location
OR
TDI
2014 A6 TDI, 2001 Jetta TDI, 2014 Passat TDI
How many people own an oscilloscope? They look kinda pricey, well, there are cheap Chinesium options, but I wouldn't know a good one from a bad one. What else are they good for? RT
I had one for a while in a snap on modus, or whatever it's called. Only used it once before I sold it.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
How many people own an oscilloscope? They look kinda pricey, well, there are cheap Chinesium options, but I wouldn't know a good one from a bad one. What else are they good for? RT
My favorite I've used is the pico-scope. It works really well for diagnosing so many things. I don't have one myself yet, but plan to get one before too long. We have one at the shop which I use a lot.
 

PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4's and the Cummins
O-scopes are all over the place in quality, weight and cost. I got several working Tek scopes for about $10 a piece. The 502A has the most sensitive diff amp front end I have ever seen. It is a sixties tube type.
cheers,
Douglas
 

CableJockey

Veteran Member
Joined
Apr 20, 2019
Location
South Dakota
TDI
2002 Golf GLS
Is it an oem alternator, or aftermarket?
It does sound like you got problems with it.
You mention that there was no ripple current when you used a multimeter? It's normal to have a little bit (max .25 vac) you'll need to put it on millivolts AC, not 12 volts...
OEM Bosch. By Non-existent, I was meaning .1 vac, but that was last spring.
I'd for sure recommend pulling the oscilloscope out.
I will plan to do this later in the week when I am less swamped by work. (Benefit of holidays)
The link is very informative.
I second the recommendation to use an oscilloscope.
There seems to be a quorum of agreement that there is something off with the alternator, so I will take heed and use my under-utilized o-scope.
Or possibly borrow the small, pocket sized one from work... Probably easier that way!
Thanks all.
 

STDOUBT

Veteran Member
Joined
Jul 30, 2007
Location
Portland, effing Oregon
TDI
dos jettas
Lol same here. If I could do it all over again I'd either be an electrician or electrical engineer.
I searched ebay for a pic of Pak's 502A, and it looks just badass. There are manuals too, so maybe we monkeys could figger it out haha.
 

PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4's and the Cummins
Lol same here. If I could do it all over again I'd either be an electrician or electrical engineer.
I searched ebay for a pic of Pak's 502A, and it looks just badass. There are manuals too, so maybe we monkeys could figger it out haha.
The old Tek tube types are solid, if limited to about 10MHz bandwidth( but quite enough to be useful ). There are some failures that are impossible to fix, one is some sort of tunneling diode...what ever in the heck that is. But beyond that all the components are discrete; Gorgeous silver plated ceramic terminal strips that hold the resistors and capacitors, rare is the circuit board in these...but there are a lot of components, and when they finally die I generally don't try and fix 'em. The 100 MHz 2246 usually gets the play. It reads out the waveform characteristics, frequency, magnitude and such.

The old Tek scopes have a further advantage; they do not require expensive probes. The usual voltage limit is 400V at the input BNC connector, and nothing between said connector and the probe contacts is required. We have some cool stuff at work, but none of it has the ability to work like that...LOL

The screen capture capability of the 502 is limited to plugging a camera into its mount. In this case a dedicated Polaroid. Have been looking for one of those for some time w/o success...LOL
cheers,
Douglas
 
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CableJockey

Veteran Member
Joined
Apr 20, 2019
Location
South Dakota
TDI
2002 Golf GLS
Managed to use an oscilloscope on my car's alternator. My 30lb dinosaur from the basement refused to turn on, but I snagged two different alternatives from work. (Timebase is different between the two: the pocket-scope is capturing roughly twice as long)
Not sure what the "diagnosis" would be, but it definitely acts weird:
At Idle:
PC-scope Pocket-scope

At 2000rpm:
PC-scope Pocket-scope

Charging voltage remains a steady 14.4vdc. Multimeter measured AC ripple fluctuates between 13mVac and 16mVac, which is 'confirmed' on the PC-SCOPE. However, visually on the Pocket-scope the point-to-point voltage is closer to 100mVac.

I am inclined to believe the inconsistent waveform on RPM change denotes a bad alternator, but it isn't all that clear why. The relative lack of AC seems to imply that the diodes are okay, and the near perfect 14.4v across the RPM range makes it appear that the regulator is functioning fine...

Any experienced thoughts?
 

pkhoury

That guy with the goats
Joined
Nov 30, 2010
Location
Medina, TX
TDI
2013 JSW, 2003 Jetta Ute, 2 x 2002 Golf, 2000 Golf
What did I do... apparently screwed up my brake booster after I swapped brake pedals for a 5 speed swap that happens in a couple of days.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
I have a VNT-15 cold side attached to a pancake pipe attached to the IC inlet hose. I have the pipe with the ridges that use the "C" clamp to attach. I tagged the throttle for 2 seconds and the pipe blew apart ( I thought the turbo gave up, the brand new turbo ) It was not the turbo, TG, so I put everthing back to together. Same problem again. I lined everything up to where it should/should stay, and installed 3 small screws to prevent the hose blowing off again. Back when I first talked about it, someone said to the effect "I ruined the hose", and my response was if I buy a new one and it blows off too, I will now own an $80.00 paperweight. Three plus years later, no piping issues, blow off, leaks, etc. Those screws were the best $0.07 (7 cents) I ever spent.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
Managed to use an oscilloscope on my car's alternator. My 30lb dinosaur from the basement refused to turn on, but I snagged two different alternatives from work. (Timebase is different between the two: the pocket-scope is capturing roughly twice as long)
Not sure what the "diagnosis" would be, but it definitely acts weird:
At Idle:
PC-scope Pocket-scope

At 2000rpm:
PC-scope Pocket-scope

Charging voltage remains a steady 14.4vdc. Multimeter measured AC ripple fluctuates between 13mVac and 16mVac, which is 'confirmed' on the PC-SCOPE. However, visually on the Pocket-scope the point-to-point voltage is closer to 100mVac.

I am inclined to believe the inconsistent waveform on RPM change denotes a bad alternator, but it isn't all that clear why. The relative lack of AC seems to imply that the diodes are okay, and the near perfect 14.4v across the RPM range makes it appear that the regulator is functioning fine...

Any experienced thoughts?
I would check your slip ring, it could be worn through in some parts which will cause a pattern like that.
I can't see the scale of the pattern, but it doesn't look too high, just it's not smooth.
 

cjolson140

Member
Joined
Nov 4, 2018
Location
WI
TDI
1999.5 Jetta
I evidently chased non-existent electrical gremlins for a half-hour:
Leaving work, my headlights wouldn't come on. It was getting dark fast and figured I needed something to light my way: flipped to high-beams. They blipped on and went dark. ***! Figured I had some screwed up electrical problem. Had a co-worker lead me home, driving with flashers.
Pulled into the garage and started digging into fuses, switches, etc., finding nothing wrong. Checked voltage at the bulbs (Something I should have done to begin with) and measured battery voltage. Checked bulb resistance.... open-circuit. On Every Single Bulb!!
Through some mystical act of Volkswagen, all four headlight bulbs popped at the same time!
To add to the frustration, I drove past 4 different auto parts stores on my way home without thinking that I would need a bulb... Let alone FOUR!
Got a ride to the nearest Autozone, swapped the bulbs, and everything works again...

Easily the most frustrating/annoying/dumb-founding "repair" I have ever done.
I’ve had that exact scenario (but in a Mazda) after driving through a flooded road. My battery/alternator light came on for approximately one minute, and I assumed it was from the belt slipping, when really the alternator somehow went full-field and burned out all the bulbs that were turned on.
 

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
Took the Beetle to VW to get the brake switch recall done. In and out in 15 mins, and of course it was free.

Spent the rest of the morning:
- replacing the backup switch - backup lights now work
- replaced bulb in one of the fog lamps (filament broke off cleanly - must have been whacked)
- replaced transmission fluid with redline MTL (already had it on hand for another vehicle that I got rid of)
- polished the headlights. DA + Meguiar's Plast-X. Came out really well.
- Fixed the rear latch on the passenger headlamp access/dust cover. No more dust getting in there.







Here it is on the street. Headlights are in the house curing as the protective coating shouldn't get wet for 24 hours. Eerie looking when you come upon the car, but it's kind of neat looking.
 
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CableJockey

Veteran Member
Joined
Apr 20, 2019
Location
South Dakota
TDI
2002 Golf GLS
I would check your slip ring, it could be worn through in some parts which will cause a pattern like that.
I can't see the scale of the pattern, but it doesn't look too high, just it's not smooth.
Scale is 50mV per division vertical on handheld scope and 20mV per on the pc scope. Not sure why the images cropped (clicking the image again from the hosting site brings the vertical scale back)
Timebase on these scopes worked a little weird, it isn't based per division, but for the entire displayed length: so 20ms on handheld and 10 on the pc scope.
Based on the car's history, I wouldn't be surprised if the alternator is original (or some form of discount-refurb) ... With 280,000 miles. So I am unlikely to dig into it too deep and just plan on a replacement.
Thanks for the confirmation that the waveform looked weird. I was unable to capture the other patterns I saw after posting, where the waveform flatlined occasionally or suddenly became much noisier. (Coinciding with rpm change)
So slip ring/brushes sound very likely.
Thanks again!
 

Judson

Veteran Member
Joined
Jan 18, 2001
Location
Cheyenne, WY
TDI
2001 Jetta
Drove her. She maxxes out at 21.5-22psi of boost - I was reading the gauge wrong. 4-bar map is on the way, 26 psi tune is already downloaded from Owain at Malone and ready for upload. Only saw one puff of smoke the entire time, and that was because I let her get out of boost then went back in suddenly.

I honestly think this is the best she's ever run. Certainly mechnically speaking, she's at the top of her game now. I have little things to take care of still, but I'm at a pretty happy place right now.
 
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CableJockey

Veteran Member
Joined
Apr 20, 2019
Location
South Dakota
TDI
2002 Golf GLS
... the alternator somehow went full field....
An interesting concept for my situation too if my theory of slip ring or brushes is accurate: voltage sags due to bad contact with rotor, regulator raises stator field, and when connection to stator improves, voltage spikes....
Whether accurate or not, it makes a small bit of sense... I need an alternator. 🤷‍♂️
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2015 Sportwagen; Golf GLS 2002 (swap from 2L gas); 2016 A3 e-tron
What did I do... apparently screwed up my brake booster after I swapped brake pedals for a 5 speed swap that happens in a couple of days.
Oh boy - I hope you don't have to replace the brake booster on the firewall; only ever taken one off a wreck where everything else had already been removed and that was less-than-enjoyable.

How did you remove the old brake pedal? I've just gone with putting a blow-torch and/or heat gun on the metal around the plastic "cup" that holds the ball-ended booster lever/arm. Then a swift yank back on the pedal - and it's come off without damaging anything (knock on wood).
 
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