Alternator stops working intermittently

[CoyneJ]

I have a 99 a4 2.8 quattro and the bat light came on because the system was not charging, battery was tested a week ago and tested 670 of 750 and holds 11.4 wile car running and not charging and 12.5 while off. when i started it up the next day it charged just fine, when i started it again the same day it did not charge until half way home when it mysteriously started to charge again. i checked the serpentine belt and it seems ok but i will change it and make sure the tensioner is ok as well. I looked around for similar problems but cant find a clear solution, i been told its the alternator but other post suggest it bad wiring or loose connection. anyone encounter a same problem?

[Wrath And Tears]

Sounds like the brush pack in the alternator is on its way out. Pretty sure you can swap a new one in versus replacing the alternator, but it also could just be loose wiring, check all grounds and and cables for tightness.

[CoyneJ]

thanks, im putting my car in service mode right now, will take out the alternator and post few pics as soon as i get it out

[CoyneJ]

133k on it

[walky_talky20]

There is a very good chance it is the brushes, if the charging is intermittent. Luckily, there is a $5 DIY to put new brushes in the Valeo units

DIY: $5 Valeo Alternator Fix

Years later, these JX94 brushes are still 5 bucks (and change), and even have free 2-day shipping with Amazon Prime:
http://www.amazon.com/Standard-Motor...s=jx94+brushes

[CoyneJ]

thanks, my friend works for foreign auto parts and got me a good deal on alternator and i think i will take it since its my daily i really need it asap

[maxiz1]

Walky_talky I actually have used your guide. Thanks a million dude!!! The only thing I did not managed to do was to desolder the brush contact. I tried using 30W, 60W and even a butane soldering iron with max setting but that damn thing simply does not melt!!! I ended up asking a workshop to do it and they managed it using some big old fashioned soldering iron which was connected to a 12V battery!!! I couldn't understand this.....

[walky_talky20]

Hmm. 60 watt iron probably wouldn't cut it. I use a Weller D550 model 240/325 watt soldering gun. They run about $50.



OP: If you got another Valeo, then I'd keep your old one around. Should you have any trouble, you'll have all the parts to fix it.

[CoyneJ]

now that i changed the alternator after the car warmed up it keeps stalling on idle, any ideas whats wrong?

[CoyneJ]

[CoyneJ]

i looked around and it seems to be a pretty common problem, should i let it "relearn" for the next two days and see what happens?

[Wrath And Tears]

I would perform a throttle body alignment if you have access to a vagcom. I assume you disconnected your battery when replacing the alternator, that would cause the car to need a TBA. What is the check engine light for? Scan for codes and report.

[CoyneJ]

ill try to scan but last time my scanner could not connect for some reason

[Wrath And Tears]

If you have an aftermarket radio there is some issue with the K-line, I don't know too much about this. Or if you have an issue with your ABS module you may need to unplug it in order to scan.

[CoyneJ]

wow unplugging the abs worked but unfortunately the codes were cat efficiency which i had for a while

[Wrath And Tears]

I should have said that with some aftermarket scanners unplugging the abs will let the scanner read. So it doesn't necessarily mean there's an issue with the abs. You will need a vagcom to perform the throttle body adaptation.

[CoyneJ]

there are some instruction on how to do it manually and there are people arguing if they actually work, is vagcom the only way?

[Wrath And Tears]

Vagcom is the only for sure way. If you are drive by cable there's a chance if you close all the doors, hood, trunk, then insert the key in the ignition and turn the key on (but engine off) and let the car sit like that for 30ish seconds that the throttle body will adapt itself.

[CoyneJ]

i went into and German car mechanic and they performed the vag com TBA and still no change...

[Wrath And Tears]

I think some more info about when exactly the problem happens would help (I'm out of ideas / knowledge at this point).

It only happens when hot?

If you give it gas does the car stay running?

Think over and go over visual everything you could have touched or disconnected when you disconnected the battery and pulled the alternator, and make sure they are connected and plugged in.

Try disconnecting the MAF when the issue occurs and see if that makes it run better (it wont run well, but it should run assuming the issue is a bad MAF).

Hopefully someone else will chime in with other ideas.

[CoyneJ]

car has no misfires at all
only when at operation temperature at idle after giving it little gas
when i give it gas and drive it its fine
i think one of hoses may have fallen off or something like that, i will get it on the lift tomorrow and make sure

[CoyneJ]

seems to only happened when i get my foot off the gas while driving, when i stop it seems to settle down at normal revs, i checked the intake and all lines but found no leak, is it possible the vagcom has been done incorrectly?

[Wrath And Tears]

Well shit. Wish I could help more but I more or less have the same issue, but far more intermittent. Mine seems worse when I have the A/C running, have you tried seeing if A/C affects the issue?

The only time I had issues that repetitive was when I had forgotten to do a TBA, so I guess it's possible that it was done wrong. They may have performed it for a Cable driven car like mine which is group...90 something instead of for a drive by wire like yours which is group 60 something.

[CoyneJ]

well thanks for the help, car works fine besides this small issue that i can live with it

[viceprp]

I would check your wiring now that you replaced your alternator. I would have someone hold the gas on 2k and let off. Try and duplicate the problem and then wiggle the connection at the alternator. Then at your grounds and too the starter.