[diesel1024]

Hey guys!

Timing belt failed on the highway a month ago, just got finished with the top end rebuild (120k miles, belt replaced at 80k 2 years ago), first time ever doing anything close to this, when I was checking out my wheel speed sensors and my pass. side exhaust leak (P.S. sounds sweet to 20 y/o me) from the manifold (I must suck at rebuilding as the car was perfect before the timing belt failed), I noticed this connector hanging down and a piece of plastic from whatever it was connected to stuck inside of it, can anyone help me find out what it was connected to? Please include photos if you can.

 

[AndreasPassat]

Looks to be the feedback wire for the alternator.
Circled in red looks to be the broken half of the connector.
Gonna need a new alternator to fix that.

 

[diesel1024]

You know what, you're absolutely right. I had a feeling my alternator was failing anyways, drove 10 hours straight and battery was at 60% or so after a full charge before I left, might have to superglue the plastic in the meantime til I can get a replacement one. Thank you for that, I was worried I'd spend way too long trying to find out.

 

[AndreasPassat]

You could probably jury rig that plug (plug with wire) with some zip ties to keep it attached/connected to the alternator until you get around to fixing the right way. Simply just plugging it in, it will come off from vibrations.

 

[diesel1024]

I'm definitely going to give it a shot, I'm trying some Krazy Superglue with the plastic piece that I got out of the connector, fit perfectly on the alternator. Leaving it for the night to dry and will connect the connector back on then and see how it goes. Haven't had that superglue fail me yet, I work with consumer electronics 🤣 I'll zip tie it too while I'm at it, hopefully it'll hold...

 

[VAGguy]

I'm definitely going to give it a shot, I'm trying some Krazy Superglue with the plastic piece that I got out of the connector, fit perfectly on the alternator. Leaving it for the night to dry and will connect the connector back on then and see how it goes. Haven't had that superglue fail me yet, I work with consumer electronics 🤣 I'll zip tie it too while I'm at it, hopefully it'll hold...
View attachment 104973

Good job. If the repair fails later, you'll need a replacement voltage regulator. Not expensive, and bonus, it will have new brushes. The hard part is removing the alternator on the V6 as it requires service position. Just make sure you clean up the slip ring that the brushes ride on before you put the new on one.

 

[diesel1024]

Thank you so much for that piece of information, I always like to repair things before I try to replace them. I'll definitely look into that more and do some research!

 

[diesel1024]

I just looked into alternators because for some reason I forgot to search the part number in eBay. So my alternator is the Bosch 120A 078 903 016 F, but when looking on eBay I found a Bosch 150A model with the model number of 078 903 016 S. I know absolutely nothing about alternators other than they act like a generator in the sense that they make power from the rotational force from the serpentine belt, any chance someone might know if it is cross compatible? I mean I have a 1200W Amp and a 12" sub in my trunk, very occasionally my lights flicker slightly, barely noticeable, but guessing my alternator isn't making enough power to support it. That 150A one is also cheaper than the 120A ones for whatever reason, so it sounds pretty good to me, and I'd be able to get one with the connector wire still attached and can cut and splice the new one on if required if the original doesn't fit. If you have any idea, please let me know, I'll be forever grateful

 

[VAGguy]

The 150a one is from the Audi 3.0 V6 used in the A6 and A4 early-mid 2000's. It looks like it would fit, but I don't know the differences between the 2.8l and the 3.0l to be sure. Waiting for someone else to chime in.

 

[diesel1024]

Just purchased a used 150 Amp Bosch alternator 078 903 016R on eBay for $40 from an A4. Came from a car with 206,xxx miles on it, so might consider rebuilding it. Currently working on trying to pull my engine up enough to do crank bearings, so I'll replace it while I'm in there. Will give updates here on fitment, hopefully others will be able to find this useful as well.

 

[diesel1024]

Got the alternator today, turns out it is still a 150 Amp Bosch alternator, but with part number 078 903 016S instead of R. There was one wire connected to it and for reference it was about 4 AWG, assuming I was measuring correctly... 0.19-0.2 inches in diameter or around 5.0-5.3mm. It arrived damaged, so I plan on just doing a rebuild. I should probably test if it fits first though.. Rebuild kit is $40, so realistically could have a fully rebuilt alternator for $80. Also for reference, my voltage regulator on this unit is Bosch F 00M 145 261. Found this rebuild kit that hopefully will work - ManiacElectricMotors on eBay / ManiacElectricMotors

 

[diesel1024]

Got my old 120A Bosch Alternator (078 903 016 F) out today, and can confirm it has the same mounts as the 150A Bosch Alternator (078 903 016S), although the terminal and connector are on different parts of the alternator (see photos), I'm sure it'll fit anyways, theres enough slack on the connector and terminal to reach. When spinning my 120A, I head an audible grinding, compared to the smooth spinning of the used 200k mile 150A Alternator, possibly newer/replaced before (not sure, regulator brushes were way more worn on this 150a than on my 120A)? My car only has 120k on it currently. I'll try to see how hard it is to do the big 3 wire upgrade to see if I'll end up doing it now or upgrade the alternator later, found a tutorial on here, but alas, no photos. Bought 4 gauge OFC wire online from an audio wire upgrade kit ~$60, from what I've heard the 120A systems come with 8 gauge, so thought rather be safe than sorry.

--Images: Back alternator is the original 120A (078 903 016 F), front is 150A (078 903 016S)
Voltage Regulator for 120A - F 00M 145 238
Alternator Cover Rear Plastic, 2.2uF Capacitor Built In with 'W' Terminal Cut Out for 120A - 0 124 515 028 / 092 ------- F 00M 146 632 (at bottom)

Voltage Regulator for 150A - F 00M 145 261
Alternator Cover Rear Plastic, 2.2uF Capacitor Built In with 'W' Terminal Cut Out for 150A - 0 124 515 007 / 382 ------- F 00M 146 639 (at bottom)

My best guess would assume based on the design and that they are identical besides model numbers is that both cover plastics are the same, I haven't found any documentation to prove this though.

Maybe someone with more experience with alternators can chime in and confirm this information, would be great to know for reference.

 

[diesel1024]

Really have rebuilt both of my alternators so far, just finished on my 120A and working on the 150A as well. Will upload both of those rebuilds as videos as well, pretty hard to find easy tutorials on these. Actually somewhat enjoyed it, not a horrible job and definitely worth it in the long run. Might end up doing a write up too if I get a chance