Yet another Mk4 alternator puzzle...

Discussion in 'VW Mk4 Jetta, Golf, New Beetle, Passat TDI forum' started by whirlybird9, Apr 6, 2017.

  1. whirlybird9

    whirlybird9 Member

    Joined:
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    Car:
    2006 Jetta Wagon MkIV BEW
    I have an 06 Jetta TDI Wagon (BEW), and after 6 months of storage, the battery was fried. After the new battery was installed, the battery symbol came up on the dash. I replaced the voltage regulator on the alternator, however the battery symbol on the dash stays lit. During an E-test I had the mechanic test the alternator and battery, and he said everything was working great. I've been driving it for a week now and I agree, the battery is holding a charge and alternator is working fine, except for the battery dash light.... and the fact that after exactly 10 minutes the ESP light comes on and the car starts driving/shifting rough (I assume this is limp mode?). If I turn the car off and back on, I get another 10 minutes of smooth driving.

    One note about the battery symbol on the dash, it is not full brightness. When I put the key in and turn it, the battery symbol appears dimly lit compared to the other symbols on the dash. When I start the car, it remains dimly lit.

    As I said, I've got a new battery, new voltage regulator in there. The code I get is 17911 - load signal from alternator terminal (P1503 implausible signal), and the snapshot shows the load signal at 0%.

    I've checked the wiring harness to the alternator based on suggestions from other forum posts, but it appears to be intact. When I read the voltage at the 2 plug harness at the alternator, it reads 14V on the wire that heads back to the dash (the wire that controls the alternator sits at 6-12V variable) I think this means that the wires are intact. One more test I did was to hack the connector and plug the alternator exciter wire in so the alternator was running, and read the voltage on the second pin coming off the alternator - it read 0V. Does this mean something in the alternator is fried, or is it supposed to be 0V

    So basically my next step is to try to replace the entire alternator, but I thought I'd check in first to see if somebody has any other tests I can run at the alternator 2 pin harness to further rule out a electrical issue (break or short somewhere between alternator and ECU) before I spend the cash on an alternator that may not be the solution!
     
  2. crsmp5

    crsmp5 Well-Known Member

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    esp is traction control... what you feel is the brakes turning on and why after 10 min is no clue... id say a critter ate a wire when in storage....

    if the steering wheel is not level.. it will turn on the esp.. say a alignment shop did not level it out.. this happens..

    so i guess a critter by cluster could eat both the clockspring harness in column and maybe the cluster harness.. to me a dim lit led is a back feed of ground
     
    Last edited: Apr 6, 2017
  3. whirlybird9

    whirlybird9 Member

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    Car:
    2006 Jetta Wagon MkIV BEW
    I think the problem is unrelated to the actual traction control system. See this link.

    http://www.seatcupra.net/forums/showthread.php?t=209472

    I was worried about critters, although everywhere that I've searched I have not found any sign if wire damage.
     
  4. Keithuk

    Keithuk Super Moderator

    Joined:
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    Car:
    2010 Golf GTD (170) CBBB
    Location:
    Stoke on Trent, England
    VAG Error Code: 17911/005379

    EOBD II Error Code: P1503

    Fault Location:
    Load Signal from Alternator Terminal DF - Range/Performance/Implausible Signal

    Possible Cause:
    Alternator faulty.
    Voltage Regulator faulty.
    Wiring/Connector(s).

    Possible Solutions:
    Check/Replace Alternator.
    Check/Replace Voltage Regulator.
    Check/Replace all faulty Wiring/Connector(s).
    Check the fuse box that is in the battery tray, it might be burnt, the fuse or the complete plastic box (pretty common failure on Sharan because it carries so much electrical load). If so, change the complete fuse box, it is not too expensive fix if this is the cause.

    Special Notes:
    When found on the BEW engine, check Measuring Value Blocks (MVB) 16, Field 1. In most cases values will be between 15% to 30% at idle. 0% could indicate a failed or incorrect alternator.

    As taken from my new Free EOBD II Error Codes software
     
  5. whirlybird9

    whirlybird9 Member

    Joined:
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    Messages:
    33
    Car:
    2006 Jetta Wagon MkIV BEW
    Possible Solutions:
    Check
    /Replace Alternator. - Alternator test said the alternator was working great.
    Check/Replace Voltage Regulator. - brushes were worn, but still had a bit of life. New regulator had the same issue.
    Check
    /Replace all faulty Wiring/Connector(s). - based on my testing I don't think there is a problem in the wires.
    Check the fuse box that is in the battery tray, it might be burnt, the fuse or the complete plastic box - no issues here, box looked great

    I've done everything in bold above. I just wanted to see if anyone had any other suggestions before I splurge and replace the entire alternator. Ideally I would know somebody with a Mk4 to do a quick alternator swap to see if that is the issue, but no such luck. Thanks!
     
  6. crsmp5

    crsmp5 Well-Known Member

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    did not tell me if steering wheel is level or not.. if its not that will turn on the esp... even in a 03 it does... dont ask how i know... and once i learned that i was able to fix 2 other cars with weird abs kicked on for no reason issues too.. its gotta be level.. id say 8* max outta wack before odd things happen.. turning both tie rods a turn in same method, one longer, other shorter you can dial it in if the alignment shop screwed it up.. the one car i learned this on would kick it on after 10 min.. but it was not level..and who would think a not level steerin wheel would effect the esp

    now.. unless you removed plastic to look.. you would not see the wires i said to look at... the cluster surround/clam shell need removed to look.. the clock spring in the steeringwheel holds the level sensor.. so.. id look real close at the harness wires to the clkockspring and to the cluster.. somewhere the 2 harnesses will join up.. nice spot for mouse nest sadly..

    and.. ahhh did ya diagnose the batt light?? unplug it.. does light go out?? if not the wire is grounded somewhere.. if out.. now grounding the wire.. does it light up fully bright?? it should.. the 1/2 dim light.. to me is a back feed of ground.. the question is.. is it the harness.. or the alt.. so test harness.. my way easy..

    now to test the idiot light portion of the alt... a test light with a real light bulb (you can solder 2 wires to a light bulb if need be).. no led.. one end alt terminal for light.. other pos batt terminal... car off light on.. start car goes completly out.. again.. if its 1/2 lit.. its a issue in alt then... a led style test light may not reflect the 1/2 dim issue.. why its gotta be a real bulb.. this is also why i think harness issue as most led do not light up partially unless its got a short/backfeed issue... like mouse pee on cluster type stuff

    ive used test light trick to limp cars cross country that had a wiring issue... sad part is when your client is cross country seeking help and you tell the shop said trick that hes stranded at.. they gave him $500 and free bulb with 2 wires soldered on for the trick learned.. they doubted me.. and well edjucation costs $ pre interwebz era.. they were going to charge him $500 to install a alt..and i bet them they were wrong and a 30 sec test was worth it... if i wrong he buy alt.. if right.. they pay him 500 and hook up a bulb between the coil and the alt.. was gas car... could use any hot w/key though.. batt only good for test.. else bulb kill batt over night..
     
    Last edited: Apr 6, 2017
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  7. whirlybird9

    whirlybird9 Member

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    Car:
    2006 Jetta Wagon MkIV BEW
    Steering wheel is level. That's an interesting one though, gotta store that in the memory bank!

    I haven't ripped the cluster surround off yet, so I'll add that to the list for tonight.

    I did some of what you said to diagnose the battery light last night... this is what I did:

    1. I unplugged the cable (2 terminals, call them ALT and BAT), battery light went out, alternator stopped outputting current.
    2. I put a test lead between the alternator and the ALT terminal (from above). The alternator spun up and the voltage at ALT was 6V (I assume this means alternator outputting about half current). The voltage on the BAT cable was 14 V, but I could not get any voltage reading from the alternator side of the BAT connection (it was 0V). And interestingly, as soon as I shorted out ALT and the alternator spun up, the battery light was on at half brightness on the dash. I then tried to take the BAT cable and put it to ground and positive terminal, and in both cases the battery light stayed half lit. I was hoping that this would have turned the light off and allowed me to drive around without the issue.

    Now the test light testing of the alternator I did not do. I will try to build the test light with a real light bulb, and test again tonight. Then I'll start ripping apart behind the cluster.

    Thanks for your help!!!
     
  8. whirlybird9

    whirlybird9 Member

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    Car:
    2006 Jetta Wagon MkIV BEW
    So I completed the extra testing on the alternator. Again, just to make sure I'm clear as to what I did, I'll call the 2 wires on the alternator harness ALT and BAT, and -A for the alternator side of the connection, and -H for the harness side of the connection. Some of this I mentioned before but I'll summarize it all here again.


    1. When the harness is plugged in, the battery light (BL) glows half bright with key turn, and stays half bright with car on.
    2. when the harness is unplugged, BL turns off
    3. When I short the connection between ALT-A and ALT-H, the alternator engages and winds up. BL turns back on to half bright.
    4. If I take BAT-H, and put it either to ground or to +terminal, nothing changes on BL (but the voltage reads +12 on the BAT-H terminal).
    5. I created a test light (TL) as you describe in the previous post, and connect it from BAT-A to the positive terminal, and the light glows, with car ON, and car OFF, but very dimly.
    6. When I short BAT-A to ground with the TL, it doesn't glow at all. (or maybe its just too dim to see).

    One last random thought I had is about the alternator grounding. I know it grounds through the mounts, but what if there is corrosion there and its not grounding very well. Any idea what the symptoms would be?

    So I think based on what you said, since the test light glowed, but only slightly, with BAT-A connected to + battery terminal, with both the car off, and car on, I'm thinking somethings fishy with this circuit in the alternator. I found a used alt I'll probably buy to test it out, so I'll try that out after I pick it up tomorrow afternoon.
     
  9. crsmp5

    crsmp5 Well-Known Member

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    correct id assume alt...

    there are 3 wires.. big red that goes to batt

    the blue which is idiot light

    the other goes to computer to tell if it has a load on it... the 90a ones.. yours is 120a is a w terminal for the tach of those cars they came on.. some stores will try to sell you a 90a alt.. it will not function correctly..

    one more test... but look to see if has fuse first.. older cars that lacked a fuse, you ground that big red wire out to look for massive sparks... harnesses corrode.. and shorting it out makes the corroded section pop and blow like a fuse :) it will show 12v.. but passes very little amperage acting like bad alt.. the 81-84 rabbits made in pa this is a must test.. they use a steel collar to "patch" it into the main harness.. they corrode and will make your car quit running when it really fails..

    the blue wire.. it does not need to be 12v..its the ground lead to the led/bulb in dash. .alt not turning its a ground.. once running it turns to power shutting light off.. any amout of power turns it off as it looses ground ;) on the alt.. the wire with key on should show some kind of voltage thru its led/bulb in dash.. led light up at 0.7v.. i just do not know what voltage they are running internal pieces in the cluster.. i can beleive 6-7v though so the 6v number sounds good to me

    can the alt corrode to mounts.. sure... so can grounds on engine, fram rail so on... add a ground... to test break out your jumper cables.. use the one batt to alt case... 30 sec test to weed it out.. this is also a test for i think my starter is bad.. incase its just a bad ground wire.. :)
     
    Last edited: Apr 7, 2017
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  10. whirlybird9

    whirlybird9 Member

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    Car:
    2006 Jetta Wagon MkIV BEW
    Picked up a used original alternator today, put it in and started to pray! With the key turned, battery light lit up bright on the dash, and once the car started, it went out!!! Set the timer for 10 minutes and went for a drive. 10 minutes later, no ESP light and no rough shifting (no limp mode!). Probably should have done that sooner! Thanks to crsmp5 for your help! I definitely understand the alternator circuit a lot better, and learned a few new tricks along the way!!
     
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  11. chacaocop

    chacaocop Member

    Joined:
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    Car:
    Jetta/2000 (totalled by my son) Jetta/2006 (not letting my son drive this one) Jetta/2000 This will be my third TDI.
    Location:
    McKinney, TX
    So the Alternator installed was a 90Amp one correct? Once you changed it for a 120A the problem went away. Just confirming.
     
  12. crsmp5

    crsmp5 Well-Known Member

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    no i think he "rebuilt" his stock 120.. then the light was dim... i bet 1 of the wheat stone bridge diodes was bad, this put a wacky current into the system the traction control disliked.. very small eddy type current into the ground.. nuff the electronics disliked its signal.. i know of a 90 passat that had a goofy issue till a different alt was installed.. and all of a sufddent problem gone.. but alt worked perfectly with no excuse to even try a different one.. but in chasing the issue the alts power wire was not reinstalled at one point and issue went bye bye.. so light bulb in head turned on, try different alt...

    wheat stone bridge .the part that converts the ac current into dc shaped like a dimond.. all 4 points is a diode and off the middle 2 of 4 gives a dc voltage... if 1 of the 4 failed you would power the ground via ac current.. ac having a pulse so as the led went to light up it would go out, aka dim led... neat theory... if you understand electronics...
     
    Last edited: Apr 19, 2017
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