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    Thread: Alternator harness

    1. Member pod-mods's Avatar
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      06-05-2016 09:19 AM #1
      Recently the car was stuttering under hard acceleration and battery voltage dropped, I have a batt gauge. Got harness replaced and symptoms are gone but this must be happening to others with or without symptoms.

      Check your fuse box on top of the battery. The alternator harness wire turns silver after many years of use. Your battery volts will drop also and you can see it with a gauge. I changed this harness and symptoms went away. It's the thick gauge wire all the way to the left. This needs to be changed with a new alternator. Many people prob don't know their harness is causing high resistance affecting the quality of smoothness. The hotter the car gets the worse it gets if you have this issue. More RPMS, is more electricity and more resistance. There is no CEL for this. The harness should be copper colored, if it turns silver it's old and needs to be swapped. If you drive low Rpms all the time you won't notice. But it's an R, who does this?

      The harness is around $90 and car has to be in service mode to get to the alternator. This is my 2nd alternator and kept my original harness when replaced, bad idea.

      Anyone can check if they have this issue, takes under 20 seconds to pop the hood and open the fuse box to see what color your harness cable is. I expect most to be silver not copper, but whether you have symptoms or not depends on severity.

      Hope this helps someone having the same issue that I had.

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    3. Member vr6fanatic's Avatar
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      06-05-2016 01:11 PM #2
      Quote Originally Posted by pod-mods View Post
      Recently the car was stuttering under hard acceleration and battery voltage dropped, I have a batt gauge. Got harness replaced and symptoms are gone but this must be happening to others with or without symptoms.

      Check your fuse box on top of the battery. The alternator harness wire turns silver after many years of use. Your battery volts will drop also and you can see it with a gauge. I changed this harness and symptoms went away. It's the thick gauge wire all the way to the left. This needs to be changed with a new alternator. Many people prob don't know their harness is causing high resistance affecting the quality of smoothness. The hotter the car gets the worse it gets if you have this issue. More RPMS, is more electricity and more resistance. There is no CEL for this. The harness should be copper colored, if it turns silver it's old and needs to be swapped. If you drive low Rpms all the time you won't notice. But it's an R, who does this?

      The harness is around $90 and car has to be in service mode to get to the alternator. This is my 2nd alternator and kept my original harness when replaced, bad idea.

      Anyone can check if they have this issue, takes under 20 seconds to pop the hood and open the fuse box to see what color your harness cable is. I expect most to be silver not copper, but whether you have symptoms or not depends on severity.

      Hope this helps someone having the same issue that I had.
      Yes I replaced my harness roughly two years ago. It was the culprit.
      Many people enjoy eating apples and oranges, but in the end they are still… just apples and oranges. The R32 is passion fruit. . Live Long and Prosper.

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      06-05-2016 01:37 PM #3
      Going to check on that
      thx for posting.

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    6. Member
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      06-05-2016 01:59 PM #4
      They're all silver...


      Sent from my iPhone using Tapatalk

    7. Member Iku's Avatar
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      06-05-2016 02:28 PM #5
      Quote Originally Posted by Brake_Dust View Post
      They're all silver...
      Wire colour, not crimp colour.

    8. Member
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      06-05-2016 03:22 PM #6
      Quote Originally Posted by Iku View Post
      Wire colour, not crimp colour.
      I totally misread that

      Mines fine @130K

    9. Member pod-mods's Avatar
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      06-11-2016 09:27 AM #7
      Quote Originally Posted by Iku View Post
      Quote Originally Posted by Brake_Dust View Post
      They're all silver...
      Wire colour, not crimp colour.
      Yes exactly. As I stated these start out copper and fade to silver. The wire inside the crimp is visible. Ever have a train set when you were a kid? The same thing would happen to the transformer wire ends after a year or so of use and I had to clip the ends and shorten the wire to get to the copper. I don't recommend this for your car though.

      If you are over 100k and have your original harness without issues then you are most likely not FI'd. I think the turbo and high HP speeds up the issue. As soon as I started going into boost is when I felt it. Otherwise it wasn't noticeable under normal driving. The car gets hotter when FI'd, and most likely exasperated the issue for me. Pretty sure they are related.

    10. Member pod-mods's Avatar
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      06-11-2016 09:32 AM #8
      Quote Originally Posted by Brake_Dust View Post
      They're all silver...


      Sent from my iPhone using Tapatalk
      Wow for 130k these look new!

    11. Member vr6fanatic's Avatar
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      06-11-2016 10:10 PM #9
      Here's mine Back in January of 2015



      I started to smell something burning.



      New and old.



      Many people enjoy eating apples and oranges, but in the end they are still… just apples and oranges. The R32 is passion fruit. . Live Long and Prosper.

    12. Member pod-mods's Avatar
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      06-12-2016 12:47 PM #10
      Quote Originally Posted by vr6fanatic View Post
      Here's mine Back in January of 2015



      I started to smell something burning.



      New and old.




      Mine looked exactly like that. All melted/warped plastic as such. I was about to pull the trigger on the fuse box for $85 but luckily found and original OEM new fuse box from eBay for $23.00. Wonder how many people have this and don't know?

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      10-10-2016 07:44 PM #11
      I have only 61,000 miles and just noticed a burning "electrical" smell.
      I gotta check this out.

      Thanks!

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      10-12-2016 12:33 PM #12
      I changed by battery-mounted fuse holder on June 2015, and the plastic around the black wire and the lid is melted again. *sigh*

    15. Member pod-mods's Avatar
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      11-02-2016 06:21 PM #13
      Quote Originally Posted by jmkowalski View Post
      I changed by battery-mounted fuse holder on June 2015, and the plastic around the black wire and the lid is melted again. *sigh*
      How many miles did u log since June 2015?
      Are u boosted?
      Do u drive it hard?

      Mine is holding up so far at 77k now but this is my 2nd vehicle and I only do maybe 3,000 miles a year at most. I think putting her around like a grandpa would make it last longer but this feat is near impossible with the vehicle. It is warm to the touch after I drive it. The harder I push her, the warmer it gets. I think there's a relationship between high Rpms and faster wear which really sucks because this car was built to run.

    16. Senior Member PowerDubs's Avatar
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      11-02-2016 07:45 PM #14
      Holy crap- Podmods is still alive!! How you doing?
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    17. Member Auzlndr's Avatar
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      11-03-2016 10:29 AM #15
      Quote Originally Posted by pod-mods View Post
      How many miles did u log since June 2015?
      Are u boosted?
      Do u drive it hard?

      Mine is holding up so far at 77k now but this is my 2nd vehicle and I only do maybe 3,000 miles a year at most. I think putting her around like a grandpa would make it last longer but this feat is near impossible with the vehicle. It is warm to the touch after I drive it. The harder I push her, the warmer it gets. I think there's a relationship between high Rpms and faster wear which really sucks because this car was built to run.
      I'm stock and at 79k. I'll start trying to remember to either touch-test after driving, or keep my infrared thermometer in the glove box, just to see. I can be spirited, but it's also rainy up here now and I'm seeing more cops out (read as: "driving closer towards 'moderately'"). I DD mine, but most of last year I didn't get that many miles as I was working mostly from home at the time, which is not the case now. So far, mine has not melted, and the wires still appear healthy. I did just replace my battery, which was going south but had not gotten the point of failure, wondering if driving on one which is on its way to 'bad' does anything to mess with load and accelerate a fail condition.

    18. Member pod-mods's Avatar
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      11-03-2016 02:15 PM #16
      Quote Originally Posted by PowerDubs View Post
      Holy crap- Podmods is still alive!! How you doing?
      Yes sir still alive and kicking! Haven't really been on the forms as much as the old days. How have you been man?

    19. Member pod-mods's Avatar
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      11-03-2016 03:26 PM #17
      Quote Originally Posted by Auzlndr View Post
      I'm stock and at 79k. I'll start trying to remember to either touch-test after driving, or keep my infrared thermometer in the glove box, just to see. I can be spirited, but it's also rainy up here now and I'm seeing more cops out (read as: "driving closer towards 'moderately'"). I DD mine, but most of last year I didn't get that many miles as I was working mostly from home at the time, which is not the case now. So far, mine has not melted, and the wires still appear healthy. I did just replace my battery, which was going south but had not gotten the point of failure, wondering if driving on one which is on its way to 'bad' does anything to mess with load and accelerate a fail condition.
      I had the same situation as you with a low battery because car would sit for maybe 10 days and battery would be dead from the lowJack. Alternator always was my charge up method while driving, rather then a battery tender. Alternator went some time after and didn't change the harness. Big mistake. Now I know that a new alternator means always new harness too. Also using a battery tender now.

      Guys talk about the harness being too low gauge and going with a home made larger gauge harness with success. Most likely that's the case. That the oem harness can't handle high electrical loads over extended periods without melting the fuse housing. Mine got so bad that the car just died while driving it hard. After sitting a half hour it cooled off and the resistance improved allowing me to drive it home. It was driveable but when dipping into boost car stuttered and fell on its face. Similar to failing MAF performance. Except unplugging MAF didn't ditch the symptoms in stand alone.

    20. Member Auzlndr's Avatar
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      11-07-2016 12:34 PM #18
      Quote Originally Posted by pod-mods View Post
      I had the same situation as you with a low battery because car would sit for maybe 10 days and battery would be dead from the lowJack. Alternator always was my charge up method while driving, rather then a battery tender. Alternator went some time after and didn't change the harness. Big mistake. Now I know that a new alternator means always new harness too. Also using a battery tender now.
      Near as I can tell, my battery wasn't *that* far gone, I was seeing some weirdness that didn't make sense, and I basically caught the battery right at the end of its service life before it would've left me stranded somewhere. I got *really* luck cuz I'm a fkn nerd and data, baselines and deviations I tend to pay too much attention to. If you want to see how it manifested:

      https://forums.vwvortex.com/showthrea...de-Voltage-dip

      I believe I've largely got the issue corrected with just a battery, I'll be updating the thread in a few days, I want to give at least a week of driving on the new battery before I circle back with data there.

      As for my battery-top fuse box, I checked twice over the weekend when getting home, freeway -> ~2 miles surface streets, and getting the IR thermo up real close (to reduce the width of its sample area) I was showing 1st sample 100*F and 105, and 2nd sample 109 and 109, temps taken on the binding post/nut on both sides of S177 (the first/largest fuse), where the harness comes on-board. Not too hot to touch. My fuses also show no signs of warping or discoloration.


      Quote Originally Posted by pod-mods View Post
      Guys talk about the harness being too low gauge and going with a home made larger gauge harness with success. Most likely that's the case. That the oem harness can't handle high electrical loads over extended periods without melting the fuse housing. Mine got so bad that the car just died while driving it hard. After sitting a half hour it cooled off and the resistance improved allowing me to drive it home. It was driveable but when dipping into boost car stuttered and fell on its face. Similar to failing MAF performance. Except unplugging MAF didn't ditch the symptoms in stand alone.
      I do agree that we've got a system that could've used a bit more thought and engineering with better vision on the future and long-term durability. You have fixes like this, which I think are a bit overkill:

      https://forums.mwerks.com/showthread....ttery-fuse-box

      He makes a case starting with this:
      Keep in mind that the 120amp alternator battery fuse box has the following fuses.
      One 150A
      One 110A
      One 40A
      Two 50As
      Three 30As.
      Equals 490 amps.
      I started diving in to where I disagreed with a lot of the logic on that page, and it was straight down the rabbit hole for 20 minutes so I deleted a few pages of dialog I was writing up on the topic, unless someone *really* wants to hear it.

      While we're on the topic, and to help me better round out my understanding of the battery-top box:
      The alternator wire is the black wire coming in the back side (nearest cabin) of the left fuse (S177)? The front side (nearest bumper) connects to battery, and starter? Or is it alternator -> starter -> back side of S177? Different threads have different statements, and some even show conflicts inside them as to what the actual path is. As S177 is labeled "Generator (GEN) (120 Amp.)" I'm trying to figure out where the fuse fits in its path, if current comes in the back (black) wire, through the 150A fuse, out the front to B+ and from B+ to starter, or... some other way. Any light to be shed on this would help a lot, if nothing else than in figuring out how overkill the above-linked assessment really is. I believe we need a better solution than stock, I'm not so sure we need to go as far as the author of the link does, trying to figure where the balancing point would be.

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      11-08-2016 08:44 AM #19
      The alternator is connected straight to to fuse S177. (wiring diagram says 25.0mm^2 wire, which is appx. 4AWG.) There are no branch circuits.

      The battery post wire (the big fat one that's actually part of the clamp) is connected straight to the starter. No branch circuits. 35.0mm^2 wire.

      The wire that runs from the battery cable post to the fuse box...that's the cars power. It's 16mm^2 (appx. 6AWG)

      At least that's how the wiring diagrams show it for the 3.2L, and how it physically is on our cars.

    22. Member Auzlndr's Avatar
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      11-08-2016 11:41 AM #20
      Quote Originally Posted by jmkowalski View Post
      The alternator is connected straight to to fuse S177. (wiring diagram says 25.0mm^2 wire, which is appx. 4AWG.) There are no branch circuits.

      The battery post wire (the big fat one that's actually part of the clamp) is connected straight to the starter. No branch circuits. 35.0mm^2 wire.

      The wire that runs from the battery cable post to the fuse box...that's the cars power. It's 16mm^2 (appx. 6AWG)

      At least that's how the wiring diagrams show it for the 3.2L, and how it physically is on our cars.

      Perfect, I finally arrived at that late last night, after finding some vids on YT that showed an alternator wire replacement. And, since that's the case, the math appears wrong in the 'mwerks' fix link.

      Any idea what "S162. Glow plugs (coolant) (50A)." is for? Not being a TDI 'glow plugs' doesn't make sense. I tried to google around for something relating to pre-heating or fast-heating coolant in a VR6 but didn't see anything plausible.

    23. Member Jo|\|'s Avatar
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      11-08-2016 12:25 PM #21
      Quote Originally Posted by Auzlndr View Post
      Perfect, I finally arrived at that late last night, after finding some vids on YT that showed an alternator wire replacement. And, since that's the case, the math appears wrong in the 'mwerks' fix link.

      Any idea what "S162. Glow plugs (coolant) (50A)." is for? Not being a TDI 'glow plugs' doesn't make sense. I tried to google around for something relating to pre-heating or fast-heating coolant in a VR6 but didn't see anything plausible.
      SAI

      Update:

      J299 is the relay, V101 is the pump

      Last edited by Jo|\|; 11-08-2016 at 12:31 PM.
      -Jon

    24. Member Auzlndr's Avatar
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      11-08-2016 12:28 PM #22
      Quote Originally Posted by Jo|\| View Post
      SAI
      Thank you, Jon. I'm working on factoring what one could realistically expect to see, load wise, at any point in time. This helps.

    25. Member Jo|\|'s Avatar
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      11-08-2016 12:33 PM #23
      Quote Originally Posted by Auzlndr View Post
      Thank you, Jon. I'm working on factoring what one could realistically expect to see, load wise, at any point in time. This helps.
      Rehosting since I hate photo bucket.




      Standard fuse applications
      Coolant fan (S180) 30A
      ABS (S179) 30A
      ABS-hydraulic pump (S178) 30A
      Metal fuse applications
      Generator 120 Amp (S177) 150A
      Interior relay panel (S176) 110A
      Coolant fan and control module (S164) 40A
      Fuel pump relay (S163) 50A
      Secondary air injection relay (S162) 50A

      The max that should be seen is 340A. That would require the cooling fans on full, boths wipers on full, seat heaters, mirror heaters, hvac fans on full, sunroof opening, both windows going up/down, haldex engaged, SAI running, ABS stepping in, and the high beams on.

      Pretty sure that's impossible to do while keeping your hands on the wheel and avoiding the crash.
      Last edited by Jo|\|; 11-08-2016 at 12:44 PM.
      -Jon

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      11-08-2016 01:22 PM #24
      Thanks again, Jon.

      The main problem I'm seeing with the mwerks.com 'fix' is that he totalled all the fuses, came up with 490 amps, and assumed that the front bus bar would be expected to carry all that, and required re-engineering.

      Since we know the alternator comes in on the back side of S177, that 150A fuse is covering the feed coming from the alternator, on the chance that enough circuits are active and drawing enough to exceed 150A in total, but not enough to blow their individual fuses, S177 would blow, protecting the alternator, and you'd still have limited battery power to at least move to a safe location to shut down. This also protects the car in case the cable going from the battery to the starter were to arc to ground, you could melt through important metal components (like "subframe").

      S177 is the feed line, and it's 150A total has no business being in the total of 490 amps (which he saw as crossing the front bus bar), which makes me wonder how the mwerks author and his 2 audio enthusiasts totally missed this. It would make sense if the battery line was the sole feed and all current crossed back towards the cabin, but S177's flow is the opposite direction.

      I have a massive, rambling draft written up going over all this, examining all the circuits listed. Example: There are two fan circuits, 30A and 40A, which I believe cover low and high speed circuits, not one-fuse-per-fan. This means only one of those circuits runs at a time, so that drops the total of "how much at once is possible" some, at least 30A. But, VW seems to have used the reasonable '25% overhead' in their fusing, so constant load in a healthy vehicle could be expected to be a minimum of 25% less than fuses show, and their use would therefore be 25% less carried on the front bus bar.

      The SAI should only run when cold, and the fans should never run when its running in a cold car, unless you start cold on a hot day and have your AC on already or turn it on immediately. But, you're also not likely triggering your ABS in that period immediately after start, either. And, actually, two fuses are for ABS. Not sure if those circuits are always live, or only when you're doing something that calls ABS to life (or, one, the pump, may be perpetual and the other only as-needed, don't have my Bentley handy while I'm drafting this, notes on what I need to go back and fill in).

      Plus, as you note, a lot of systems manually controlled would need to be active to get close to the 110A seen on S176. And again, that's 110 to blow, they're expecting less for normal operation.

      While the fix is interesting, the more I look in to the nature of our vehicles the more I think it's indeed overkill. When we look at the failures, it's the cable coming in, which can happen as stuff ages and connections are less pristine and more polluted by contaminants which causes resistance to increase which causes heat. Of all the pictures I've seen on google, it's the input cable that gets damaged. It's not the anemic little front bus bar that the mwerks author pinpointed as being a weak link that needed upgrading. Example:
      http://www.kcbmwclub.com/gallery/d/46522-2/IMG_5120.JPG

      If a fix is to be fabricated, it needs to be on the supply side, not the distro bar, IMO.

    27. Member tiiger's Avatar
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      11-08-2018 09:00 AM #25
      I know this is a zombie from 2016, but lots of good info, and might as well not add an orphan thread.

      When I had the car in for some other service a couple of months back, the guys noticed that the alternator harness was running hot, and suggested replacing it. Battery was also on its last legs (6 years old), so I figured I'd replace all the cables at the same time i replaced the battery.

      So, I'm just in the midst of this...

      The other cables are easy to replace, but the alternator harness goes deep under the front of the engine. Wondering if anyone has tips or a DIY on replacing it. What needs to be removed?

      Quote Originally Posted by pod-mods View Post
      The harness is around $90 and car has to be in service mode to get to the alternator.
      And regarding this quote... Does this mean it needs to be in service mode just to replace the harness, or only when REPLACING the alternator?

      Anyway, any tips/tricks/tactics would be great.

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