Alternator going - Strange codes in engine module

[Occams_Razor]

Hello all,

My alternator has been acting up, (Alternator Workshop in the MFA and whining in the radio), even though it still puts out the correct voltage to charge the battery, etc.

I have now started getting a flashing glow plug MIL and error code in the engine module that the brake light switch is intermittent.

I replaced the brake switch for a brand new one old model one, (I bought it new from IMPEX before VW changed over to the newest versions that I swapped in last year and had never used it), and also changed the clutch switch just in case the error dealt with that instead but nothing. Code clears but comes back again after a few days.

BTW The brake lights work fine and have never failed, (unlike the time the first old switch did go bad and took out all of my brake light bulbs), and even the cruise control works perfectly code or no code.

So my question is if a faulty alternator could cause other codes due to it's flakiness?

 

[Uwe]

It strikes me as unlikely, but it would be a logical fallacy to rule it out.

-Uwe-

 

[Ol'Rattler]

Another way to state what Uwe said would be in troubleshooting, fix things you know are not working right so that you can rule those problems out before driving on with other problems.

In regards to alternators, they are actually AC generators that have 6 diodes that change AC to DC. If any of the diodes internally short, AC will be supplied to your electrical system which could cause some of the electrical components in your car to behave strangely or even damage something expensive.

The whining in your radio quite often, is a dead giveaway of AC leaking past flaky alternator diodes.

The best course of action would be to have your alternator tested...................

 

[Occams_Razor]

Another way to state what Uwe said would be in troubleshooting, fix things you know are not working right so that you can rule those problems out before driving on with other problems.

In regards to alternators, they are actually AC generators that have 6 diodes that change AC to DC. If any of the diodes internally short, AC will be supplied to your electrical system which could cause some of the electrical components in your car to behave strangely or even damage something expensive.

The whining in your radio quite often, is a dead giveaway of AC leaking past flaky alternator diodes.

The best course of action would be to have your alternator tested...................

My next step was to replace the alternator. Just need my money tree to bloom.

 

[Ol'Rattler]

Well sure. My point was that you can't really make decisions about the other DTCs until the alternator is fixed................

 

[MOGolf]

Verify brake switch operation by looking at ECM measuring block group 006.

Since you installed the old style switch, did you hold the brake pedal fully up while installing the switch?

 

[Occams_Razor]

Verify brake switch operation by looking at ECM measuring block group 006.

Since you installed the old style switch, did you hold the brake pedal fully up while installing the switch?

Switch tests out fine and yes I did hold the brake pedal up when installing, (have had to change more than a couple in the last few years).

 

[HoneyBeetle]

Another way to state what Uwe said would be in troubleshooting, fix things you know are not working right so that you can rule those problems out before driving on with other problems.

In regards to alternators, they are actually AC generators that have 6 diodes that change AC to DC. If any of the diodes internally short, AC will be supplied to your electrical system which could cause some of the electrical components in your car to behave strangely or even damage something expensive.

The whining in your radio quite often, is a dead giveaway of AC leaking past flaky alternator diodes.

The best course of action would be to have your alternator tested...................

This is VERY interesting. My father told me to check my alternator, I could have a bad diode and it may be partially working. Anyhow, is it easy to test your own alternator? I would like to try? Another thing...I was told, by MRChill that a funny noise in the radio might be a ground wire issue. I don't know, but I'd like to know.

 

[Ol'Rattler]

This is VERY interesting. My father told me to check my alternator, I could have a bad diode and it may be partially working. Anyhow, is it easy to test your own alternator? I would like to try? Another thing...I was told, by MRChill that a funny noise in the radio might be a ground wire issue. I don't know, but I'd like to know.

A reputable auto electric shop could probably check your alternator on the car for cheap. I don't know if a multi-meter could tell you if AC is leaking past the diodes or not.

Grounds are always a good thing to check. The main ground for the car is on the chassis, under the air cleaner housing. Follow the big ground wire from the starter. Were it connects on the chassis there is also a smaller wire that is probably the main ground for all the chassis electrical.

Got bitten by that one myself. I just replaced the battery that I thought was bad because sometimes the starter would just click and not turn over the engine. I would also get a check engine light and fault codes for the glow plugs but no flashing glow plug light.

Turns out that I must have not tightened the chassis ground when I had it apart when I changed my clutch. I cleaned and tightened the chassis ground and my no start problem was fixed.

 

[MOGolf]

OR, have you found the solution to this yet?

 

[2slowtdi]

I just replaced my alternator last weekend , the best buy was NAPA just under 200 USD for a 2003.

Mine was making the battery light come on a just over 2650rpm not under and only when hot.
My tool for checking the battery and alternator read that everything was good,with load test and all.
The light would not come on when the AC was on or I had alot of power needs.
After replacing it everything is good no battery at and RPM.
Just another odd way for alt to act up.

 

[Occams_Razor]

OR, have you found the solution to this yet?

Not yet. Alternators are expensive! I could take it out and rebuild it but I don't have the time. I did notice that the stupid engine code tends to show up soon after I get an Alternator Workshop indication in the cluster so I think I am just going to have to bite the bullet and get a new alternator.

 

[MOGolf]

Or it could be an intermittent failure of the clutch in the alternator pulley.

 

[Occams_Razor]

Or it could be an intermittent failure of the clutch in the alternator pulley.

The pulley was making noise not too long ago so I replaced it. It has given the alternator workshop message before AND after the pulley swap.

 

[Ol'Rattler]

Or it could be an intermittent failure of the clutch in the alternator pulley.

That kind of failure would probably result in no fault codes and the battery would eventually go dead. Also I think that the alternator light would come on because there would be no alternator output.

An alternator clutch failure could be isolated by a voltage rise test.

Voltage rise test:

• Completely charge battery with a battery charger.
• Remove battery surface charge by turning headlights on for 5 to 10 minutes. (Key must be on.) Surface charge from charging is is drained off when battery voltage measures just above 12 volts.
• Measure and record voltage at battery.
• Start car.
• Measure voltage at battery.

When the car is running the voltage should rise 1 to 2 volts above battery voltage.

This test will tell you when an alternator is not charging but will not tell you if the alternators diodes are leaking A/C.

 

[jollyGreenGiant]

I bet if you put a multimeter set to Volts AC between battery posts on this car and another without problems you would see higher numbers on this one.

Also, I haven't taken one apart but my guess is that the brake switch is not a simple set of contacts, I bet there's an integrated circuit in there that is most likely susceptible to poor voltage.

Thus based on the info provided I would swap that alternator with a known good one.

Working on cars has become such a risk analysis thing huh? We should leverage the insurance industry for some slick algorithms to help our daily decisions...

 

[dzcad90]

I had my alternator for my MkIV rebuilt while I watched for $170. Took about an hour. New bearings, brush module / diode pack, and clutch pulley.

It's probalby time if your car has around 150K miles on it.

 

[Occams_Razor]

OR, have you found the solution to this yet?

Okay. Swapped out the Alternator for an O'Reilly rebuilt unit. $175.00 after the return of my core. Turns out that I had a 90 amp in the car and I bought a 120 amp one. The fit is identical so I went ahead and did the upgrade.

The bearings in the old alternator were on their last legs, (now I know what one of the weird noises from my engine was ). They sounded completely unlubricated. The new alternator was noiseless.

Other then the pain in the butt the actual remove and replace is, (I am dreading ever having to do this on my wife's New Beetle), putting in the new alternator was uneventful. The alternator workshop flash went away but I am still getting the brake switch MIL code in the ECU and the flashing glow plug indicator. (And the radio is still whining )

Any other ideas guys?

 

[MOGolf]

idea #1) check all the ground points especially under the battery
idea #2) sell it

 

[Dana @ Ross-Tech]

Do you have a VCDS scan to post?
Have you checked the Fuse panel at the battery for melting? (assuming this is a MK4 body)
I know you mentioned it, but are all of the bulbs correct in the tail light holders / sockets?

As MOGolf mentioned, bad grounds can cause serious problems. I would also check the main ground at the transmission.

 

[jetta 97]

Okay. Swapped out the Alternator for an O'Reilly rebuilt unit. $175.00 after the return of my core. Turns out that I had a 90 amp in the car and I bought a 120 amp one. The fit is identical so I went ahead and did the upgrade.

The bearings in the old alternator were on their last legs, (now I know what one of the weird noises from my engine was ). They sounded completely unlubricated. The new alternator was noiseless.

Other then the pain in the butt the actual remove and replace is, (I am dreading ever having to do this on my wife's New Beetle), putting in the new alternator was uneventful. The alternator workshop flash went away but I am still getting the brake switch MIL code in the ECU and the flashing glow plug indicator. (And the radio is still whining )
Any other ideas guys?

You said you had 90Amps. All TDI has 120Amps so you had wrong alternator anyway.
Put green switch amd only OE (dealer one) not OEM. and it will fix problem.Old one, as we know had recall so they are not good ,even new ones.

 

[Ski in NC]

Regarding AC ripple: I just went and cranked my 2001 (about 40F) DC voltage quickly went up to about 14.3Vdc. AC measured with a fluke at battery terminals was about 35mVac, leveled out at about 30mVac in 15 sec. No whine in my radio, car has been working fine.

So if you have whine in the radio, check for ac ripple. See if it higher than what I got.

 

[Occams_Razor]

You said you had 90Amps. All TDI has 120Amps so you had wrong alternator anyway.
Put green switch amd only OE (dealer one) not OEM. and it will fix problem.Old one, as we know had recall so they are not good ,even new ones.

I thought the 120 amp was standard on TDI's too but I have owned this car from the factory. This is the first time the Alternator has been swapped and it definitely was a 90 amp Bosch unit. I checked ETKA and it shows that 1.9 ALH TDI's could have 90 amp alternators, (even with air conditioning).

I got the stupid MIL light last night again and went in to measuring block 6 and found that depending on how you press the brake, (quickly hard or slow and deliberate), the value doesn't flip like it is supposed all the time so I think the next thing to replace is the brake switch for one of the newer ones, (interesting enough I had replaced a VW OE "new green" with a brand new VW OE "old purple" one. Both had the same issue.)

 

[Occams_Razor]

Regarding AC ripple: I just went and cranked my 2001 (about 40F) DC voltage quickly went up to about 14.3Vdc. AC measured with a fluke at battery terminals was about 35mVac, leveled out at about 30mVac in 15 sec. No whine in my radio, car has been working fine.

So if you have whine in the radio, check for ac ripple. See if it higher than what I got.

I will play with that and see what I get.

 

[Occams_Razor]

Do you have a VCDS scan to post?
Have you checked the Fuse panel at the battery for melting? (assuming this is a MK4 body)
I know you mentioned it, but are all of the bulbs correct in the tail light holders / sockets?

As MOGolf mentioned, bad grounds can cause serious problems. I would also check the main ground at the transmission.

I replaced the fuse panel and all of the fuses with the correct manual transmission one when I did my 6 speed swap but haven't look at them since then. I will check to make sure they are okay.

I replaced the bulbs in the tail lights with the same number ones I took out the first time I replaced the brake switch, (it burnt out all of the bulbs that time), but I might as well change them all out just to be on the save side.

I will check the grounds on the transmission and under the battery again.

 

[jetta 97]

I thought the 120 amp was standard on TDI's too but I have owned this car from the factory. This is the first time the Alternator has been swapped and it definitely was a 90 amp Bosch unit. I checked ETKA and it shows that 1.9 ALH TDI's could have 90 amp alternators, (even with air conditioning).

I got the stupid MIL light last night again and went in to measuring block 6 and found that depending on how you press the brake, (quickly hard or slow and deliberate), the value doesn't flip like it is supposed all the time so I think the next thing to replace is the brake switch for one of the newer ones, (interesting enough I had replaced a VW OE "new green" with a brand new VW OE "old purple" one. Both had the same issue.)

That is very strange on your alternator, but it is good to update to 120amps.Maybe only Wagon comes like that, since they come from Germany.

 

[NB_TDi]

Automatic TDIs have the 90A alternator. Sticks have the 120A.

 

[MOGolf]

Automatic TDIs have the 90A alternator. Sticks have the 120A.

I've seen a mixture on the ALH engines. No consistency. You might think the sticks need the 120A due to the additional heat GPs, but I've seen some with the 90A. And I've seen 120A on automatics, but my Golf has a 90A.

I've monitored cars with both. Some modified with high output aftermarket sound systems. It didn't matter. The highest current draw was the rear window heating element. At idle, the highest reported load (via VCDS) was 50something percent with everything turned on that could be. It went down at higher RPMs of course.

 

[NB_TDi]

Wow, That's odd.

 

[Occams_Razor]

Still have annoying error code

Okay.

Recap.

New 120 amp rebuilt alternator.
All grounds cleaned and fuses checked.
Brake light switch and clutch switch swapped out for new OEM ones freshly bought from IMPEX.
Swapped the pigtail and plug for the clutch switch as the one I had as from a junk yard car and looked a little too toasted for my liking.

Car still giving code that brake light switch is intermittent and flashing glow plug indicator light in cluster. MFA shows "Engine Workshop" soon after I start the car.

Clear codes and it will come back within the day.

Anybody have any ideas?