Bad Alternator?
06-27-2010, 05:01 AM
#11
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you have 4 conditions to check for:
1. is the battery no longer accepting and holding a charge (note, this does not happen suddenly, but gradually, so i doubt it) - load test to find out.
2. Is the alternator putting out A/C voltage - not sure where you could get access to this.
3. Is the voltage regulator and rectifier working? This is a n electronic pack that takes the AC from the alternator and makes it 14+V DC. Look at the B+ for both voltage (should be 14+ when charging) and ripple (which might mean a bad regulator. Unfortunately (for testing) a battery will often smooth out all ripple.
4. GROUND. Do you have a good solid GROUND? No return, no flow. Check the strap.
G
1. is the battery no longer accepting and holding a charge (note, this does not happen suddenly, but gradually, so i doubt it) - load test to find out.
2. Is the alternator putting out A/C voltage - not sure where you could get access to this.
3. Is the voltage regulator and rectifier working? This is a n electronic pack that takes the AC from the alternator and makes it 14+V DC. Look at the B+ for both voltage (should be 14+ when charging) and ripple (which might mean a bad regulator. Unfortunately (for testing) a battery will often smooth out all ripple.
4. GROUND. Do you have a good solid GROUND? No return, no flow. Check the strap.
G
06-27-2010, 07:16 AM
#12
AudiWorld Member
Thread Starter
The battery is charged and maintains 12.8 volts after a couple of hours idle, so I think it's good.
Now I need to scare up some 2x4s so I can raise the car.
Now I need to scare up some 2x4s so I can raise the car.
06-27-2010, 08:10 PM
#13
AudiWorld Member
Thread Starter
The battery is holding charge, still over 12.6v. I can't measure the alt output at the alt, it's impossible with my electronics grabbers (and I have some good ones). Regualtor is built in, can't check it. Ground is good.
Bottom line the alt has to come out.
Bottom line the alt has to come out.
06-28-2010, 03:48 AM
#14
AudiWorld Super User
Don't get to far off in the weeds ... if your battery is holding voltage satrt the car and measure the DC again .. if it is 13.5 - 15 you are okay , anything lower than that and you are looking at a new alternator ( the regulator is part of the alternator). You can try and source one of these ) or you can have the whole thing rebuilt which will include a new regulator, beartings and slip rings.
Goos luck
Goos luck
07-03-2010, 01:32 PM
#15
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Thread Starter
After getting the car in the service position, I could not see how the alternator was coming out. There were hoses in the way under and in front of the alt. So, it was time for service position 2.
07-03-2010, 03:06 PM
#16
AudiWorld Member
Thread Starter
How does one actually get the alt out of the top mount? I've pulled the bolts, and all it does is swing on the top mount. Is there a sleeve in the back of the top mount, and how do I get it out?
(edit)
Figured it out. Lots of prying, yanking, beating and I have the bloody thing out.
(edit)
Figured it out. Lots of prying, yanking, beating and I have the bloody thing out.
Last edited by radhaz; 07-03-2010 at 04:21 PM.
07-03-2010, 08:43 PM
#17
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Beat me to it, I was going to say lots of tugging, prying and pulling 
thats how mine came out.
Did you get it back in ok? My replacement had a small(2mm)flare on one side of the upper mount and it wouldn't slide into position on the car. I ended up having to file it down flush to make it fit...ah good times...
thats how mine came out.Did you get it back in ok? My replacement had a small(2mm)flare on one side of the upper mount and it wouldn't slide into position on the car. I ended up having to file it down flush to make it fit...ah good times...
07-03-2010, 09:56 PM
#18
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Thread Starter
My replacement is due tuesday, and i'll see how that goes. that is, if i ordred the right part.
Beat me to it, I was going to say lots of tugging, prying and pulling thats how mine came out.
Did you get it back in ok? My replacement had a small(2mm)flare on one side of the upper mount and it wouldn't slide into position on the car. I ended up having to file it down flush to make it fit...ah good times...
thats how mine came out.Did you get it back in ok? My replacement had a small(2mm)flare on one side of the upper mount and it wouldn't slide into position on the car. I ended up having to file it down flush to make it fit...ah good times...
07-04-2010, 11:05 AM
#20
I was driving to work this morning on the freeway when I felt a bang. I looked at the instrument cluster and saw that prnd432 was lit up. No response when put into Tip mode. The car stayed in 5th. I tried to limp it back home, but as I was driving, I saw that the battery was draining rapidly. Eventually, I had no throttle, even though the engine was still idling. I pulled over and walked the 2 miles back to the house and called a tow.
After the car was parked, I turned on the ignition, and saw that the gear indicator was normal. The car started, and I pulled it into the garage. The battery didn't appear to be charging. I measured the battery with the car running and read ~11.5 volts and falling. I hooked it up to the battery charger and the battery is now charging, but the progress is very slow, which might be normal. The battery is what came with the car when I bought it a few years ago.
If I let it charge and it doesn't reach 100% (according to the microprocessor controlled charger) I will assume the battery needs to be replaced. Is there any chance that the alternator might be good in this case? I'm not looking forward to yanking the nose off the car.
After the car was parked, I turned on the ignition, and saw that the gear indicator was normal. The car started, and I pulled it into the garage. The battery didn't appear to be charging. I measured the battery with the car running and read ~11.5 volts and falling. I hooked it up to the battery charger and the battery is now charging, but the progress is very slow, which might be normal. The battery is what came with the car when I bought it a few years ago.
If I let it charge and it doesn't reach 100% (according to the microprocessor controlled charger) I will assume the battery needs to be replaced. Is there any chance that the alternator might be good in this case? I'm not looking forward to yanking the nose off the car.
On a 2001 A6 Avant that I worked on recently the "bang" always occured when the transmission shifted into 'limp in mode". Audi's technical literature says that in "limp in mode" the transmission makes its shifts with pump hydraulic pressure raised to the maximum, hence the bang type shifts. The question is did an alternator low voltage problem cause the transmission to shift into "limp in mode"?. I would guess that it did.