Car shuts down due to over-voltage...

[gdawg'05a4]

Over the weekend, the car's components shutdown on me three times due to over-voltage (pulled DTCs) leading to no power but engine still ran. It also happened to me once last year but never did it again until a couple of days ago. The weather was quite hot and muggy and each time was after sitting idle for a long period at red lights (same scenario as last year). As I was crossing the intersection, the cluster shut off then MMI and HVAC, etc. Basically all components were shutting down one by one and leaving me with only the engine running but NO power. As I gave it throttle, the engine would only rev. Luckily these were at intersections with lights so there was no cross traffic coming and I had enough momentum to make it across and pull over.

I found a couple of old posts from others who experienced the same thing but no resolution was ever posted. Their dealers said they couldn't find anything wrong, yadda yadda, so I can only imagine there was no fix.

From the DTCs, there was too much voltage and the components were shutting down to protect themselves which makes sense. Many of the components had codes stored due to 'function limitation due to Over-Voltage' such as this:
1 Fault Found:
00447 - Function Limitation due to Over-Voltage
001 - Upper Limit Exceeded - Intermittent

From the freeze frame, it was 35C/95F.

From the CAN gateway:
1 Fault Found:
02252 - Generator
012 - Electrical Fault in Circuit - Intermittent
Freeze Frame:
Fault Status: 00101100
Fault Priority: 1
Fault Frequency: 2
Reset counter: 19
Mileage: 59796 km
Time Indication: 0
Date: 2016.07.14
Time: 20:24:22

Freeze Frame:
Bin. Bits: 01111
Voltage: 18.80 V
Count: 6

It's a scary experience when you've got no power to cross an intersection. Luckily for my family and I we were OK. I can only imagine if this happened at a busy intersection. Any ideas as to what could be triggering this? I'm thinking something with the power management system or alternator is wonky with the excessive heat from idling at a light and external temps.

She's going in tomorrow for them to look at it so hopefully they can find the root cause. I'm almost tempted to say keep it until it's fixed given the hot weather is here and I don't want another repeat of this. It's a safety issue now IMO...

[blk18tq]

yup! happen to a couple of us, It did it two me 3 times, always at night when headlights & Ac are running, my tech at audi needs to check it out still, he did mention the voltage was spiking up to 18volts, he said it could be the battery or voltage regulator needs to be replaced.. I never run the AC at night anymore, I car has been fine..
let us know what you find out.. i'll keep you posted as well..

[SwankP3RF3ct10n]

Possible Alternator issue... Although I've never heard of one putting out more voltage when it dies, it's usually the other way around.

Apparently there's an alternator regulator that could fail and cause this issue. Look at replacing that.

[gdawg'05a4]

Thanks guys. Luckily I still have warranty so I'll be making sure they get to the bottom of this. I'm thinking it's the regulator or power management component that is dying and rears it's head when it's hot out. I'll post an update once Audi has looked at it.

[S4'ed]

May not be the regulator or alternator : look for loose or corroded cable connections on the alternator, battery, starter, and the fuse panels. Also all the ground cables between the frame, and the battery, and the alternator.

[gdawg'05a4]

Just wanted to update the thread. The dealer replaced the voltage regulator. There's actually a TSB for this, 2031145/2. It seems to be a common enough issue to issue a TSB and the same voltage regulator is used across pretty much most of the models (A4, A5, A6, A7, A8, Q5, Q7). Interestingly enough it doesn't explicitly list the S4 but the symptoms are the exactly the same. It could be they don't list the 'S' variants but falls under the 'A' line. Here's the repair order:



TSB: http://www.esghotwire.com/bulletins/...TC_Present.pdf

So far it hasn't happened again and it's been hot and humid here.

[Wreckm]

About to change my voltage regulator.
Hasn't shut off on me in awhile but the heat came back and a/c on other day while charging my phone it shut off at a light..
my S is 2010 i am wondering if its this Voltage reg.
https://www.ecstuning.com/Audi-B8_S4....0T/ES2576367/

also those codes you pulled was with VAG?

[AdamInKC]

Curious, does anyone know how difficult it is to replace the voltage regulator? I have a new one on the way and would like to better understand what I’ll be up against.