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AudiDoc
AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 6426
Experience:  I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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Audi A4 Quattro: Just recently had alternator replaced due

Resolved Question:

Just recently had alternator replaced due to battery not keeping charge, battery tested ok. Picked up car from shop and was ok for 3-4 minutes then battery light began to flash intermittently. Flash at first was at deceleration. A bit farther and I notice voltage dropping and battery light flashing more consistently until light stayed lit even while driving and voltage dropping quickly.

I pulled over before it would die and received a jump a few minutes later, after removing jumper cables voltage continued dropping until dash instruments were inoperable. I held down accelerator at 1k rpm for about a minute and suddenly voltage jumped back up and stayed fine while idle.

I was less than a mile away from home so I drove car home and as soon as i accelerated to 2-3k rpm light started flashing again until it stayed lit and barely made it into parking lot.

I have done some reading and found the most alike symptom to be tied to the serpentine pulley belt. Does this sound like a likely culprit?

I also read that the alternator fuse may have been blown but this seems less likely as voltage is fine at idle and does not drop at all.

Expert advice would be greatly appreciated.

Thank you
-Aaron
Submitted: 1 year ago.
Category: Audi
Expert:  AudiDoc replied 1 year ago.

AudiDoc :

Hello, I'm Jason. I will do my best to answer your question quickly and accurately using the information you have provided.

Customer:

Hi Jason

AudiDoc :

Hello there. Still reading through actually

Customer:

No problem

AudiDoc :

Ok, let me ask the first obvious question. The alternator you bought? Audi OE or Bosch reman?

Customer:

I'm not sure, the repairs were done at the VW dealership that my father works for

AudiDoc :

ah, gotcha, so I'll assume it's a factory alternator

Customer:

He is currently trying to get a hold of the mechanic who worked on it

Customer:

is having hard time contacting him though

AudiDoc :

sure, understood. These are relatively simple systems

AudiDoc :

I know you mentioned the belt and pulley, but if the belt is turning ok, not jumping or making noise, that's likely not the problem

Customer:

We noticed nothing odd with the belt

AudiDoc :

what's voltage at idle?

Customer:

We didn't have a meter on hand =\

AudiDoc :

Ok, so you're looking at the dash gauge, I assume

Customer:

Yea

Customer:

just watching it fall... lol

Customer:

after revving engine tho it jumped up to normal though and did not falter

Customer:

while idling

Customer:

it took a minute of revving at low rpm though at least

AudiDoc :

let me take a quick look at the diagram. Honestly, this sounds like a faulty alternator

AudiDoc :

somewhat rare, but not impossible

Customer:

I was reading someone with an alike issue and they replaced alternator 3x only to notice that the alternator fuse was burnt out

Customer:

Is this a possibility?

AudiDoc :

no problem....just going through the diagram now. Few minutes

Customer:

np

AudiDoc :

oh, which engine please?

Customer:

1.8T

AudiDoc :

thanks

AudiDoc :

There really isn't a dedicated alternator fuse on this car.

Customer:

ah

AudiDoc :

since the exciter wire goes right to the instrument cluster

AudiDoc :

and the main power wire......

AudiDoc :

hmmmmm

AudiDoc :

might want to take a look at the large connection on the starter as well

AudiDoc :

make sure that's not loose

AudiDoc :

since that chains to the large alternator connector

AudiDoc :

I've seen this exacty 2x

Customer:

i did notice that the little shield that sits in front of the windshield at the back

Customer:

was rubbing on a wire

Customer:

i taped it up

AudiDoc :

The lower cowl plastic shield?

Customer:

it had become disloged

Customer:

yea

Customer:

i secured it though and hasn't come loose since

Customer:

the wire was connected to the battery

AudiDoc :

yeah, that shouldn't be an issue, as this wiring goes through the front side of the engine ECU box, then down into the car

AudiDoc :

oh, that cable

Customer:

it appears to still be secured

AudiDoc :

Here's what I would do

AudiDoc :

have the car running. Check voltage at + and- on the battery itself.

AudiDoc :

Record voltage at idle

AudiDoc :

Then leave negative probe on the negative terminal

AudiDoc :

Move positive probe to large alternator connector

AudiDoc :

see if there's a significant voltage change checking it that way (over 0.2v)

AudiDoc :

if there is, there's a loose connection

AudiDoc :

If they're both dead-on, replace the alternator again

Customer:

If alternator tests fine, what would be your next course of action?

Customer:

and there isn't a loose connection at battery

Customer:

or will that pretty much sum it up

AudiDoc :

it's only going to be one of these two issues, I'm sure

Customer:

since voltage dropping so quick I can't see it being any low voltage fuse

Customer:

am i correct in thinking that?

AudiDoc :

yes, correct, not a fuse

Customer:

ok, I will pass this info along and make sure that it's done and hopefully won't have to go through this again lol

AudiDoc :

I well understand. Hope it goes smoothly

Customer:

been without it for about a month

Customer:

as do I

Customer:

You were very helpful, I appreciate it

AudiDoc :

Ironic....I actually drove mine home tonight. Usually drive an Allroad or TT

AudiDoc :

TT away for winter, Allroad under the knife

AudiDoc :

and glad to ehlp

Customer:

lol I love the car despite this issue and the high mileage

Customer:

still runs like a kitten

Customer:

anyways, I will let you go, have a pleasant evening

AudiDoc :

Great to hear. Mine is kind of a shop beater wagon. Low, V6, 5-spd, plasti-dipped black, tinted.

AudiDoc :

ciao XXXXX XXXXX

AudiDoc :

good luck

Customer:

take care

AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 6426
Experience: I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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