Start/Stop Query

[Wesley949]

Last weekend, about 3pm, without starting the vehicle since the previous night, went out to hoover the interior and clean it, keeping the doors open and the Interior lights staying on.  Afterwards, I then inflated my tyres but to start the Ignition only so the electric compressor can function.  Upon completion, I reset the Tyre Pressure monitor within the MMI and then started the engine only for an alarm to sound, and on the Dash screen, it stated "Start/Stop Fault - System Unavailable".  But there were no Amber/Red lights displayed.

I turned off the engine and Ignition and restarted the car an this time, no warning.  I then went for a drive, to get the vehicle to operating temperature so the Start/Stop system would work and it did, it worked as it normally does.  Even to date, there has been no further indication of any warning and I do not have any Diagnostic kits so I cannot check to see if there are any Fault Codes listed on my vehicle.

One Audi forums (not this one) stated that on an S3, the Start/Stop fault on there car was due to a faulty Crank Sensor and a Low Battery voltage.

I can only assume that the Battery voltage aspect was what played a part on my vehicle but the car is not quite a year old yet so I hope my Battery isn't faulty.  Would this cause any fluctuation with the Start/Stop system?  Should I have my Audi Service Centre look in to it or is that too extreme?

[Big_dom91]

Iv had similar issues with my car doing that but fortunately it has been quite awhile since it last done it,however id watch out as once or twice when it displayed this message the engine cutout but other than restarting the engine manually there has bever been any other problems  

[Steve Q]

On 11/16/2017 at 11:44 AM, Wesley949 said:

Last weekend, about 3pm, without starting the vehicle since the previous night, went out to hoover the interior and clean it, keeping the doors open and the Interior lights staying on.  Afterwards, I then inflated my tyres but to start the Ignition only so the electric compressor can function.  Upon completion, I reset the Tyre Pressure monitor within the MMI and then started the engine only for an alarm to sound, and on the Dash screen, it stated "Start/Stop Fault - System Unavailable".  But there were no Amber/Red lights displayed.

I turned off the engine and Ignition and restarted the car an this time, no warning.  I then went for a drive, to get the vehicle to operating temperature so the Start/Stop system would work and it did, it worked as it normally does.  Even to date, there has been no further indication of any warning and I do not have any Diagnostic kits so I cannot check to see if there are any Fault Codes listed on my vehicle.

One Audi forums (not this one) stated that on an S3, the Start/Stop fault on there car was due to a faulty Crank Sensor and a Low Battery voltage.

I can only assume that the Battery voltage aspect was what played a part on my vehicle but the car is not quite a year old yet so I hope my Battery isn't faulty.  Would this cause any fluctuation with the Start/Stop system?  Should I have my Audi Service Centre look in to it or is that too extreme?

I would have to agree and suggest this issue was caused by low battery voltage. It's amazing how many electronic issues can be traced back to a low battery. If the battery is low then this will prevent the start stop to not work as it takes alot on the battery if that makes sense. 

Sounds like everything is back to normal now though :) 

Cheers

Steve

[Beezil]

On 11/12/2017 at 10:05 AM, Steve Q said:

I would have to agree and suggest this issue was caused by low battery voltage. It's amazing how many electronic issues can be traced back to a low battery. If the battery is low then this will prevent the start stop to not work as it takes alot on the battery if that makes sense. 

Sounds like everything is back to normal now though :) 

Cheers

Steve

I would concur with this. There is so mu h load on the electrical system these days that it's possible to get minor current drops which will be enough to flag a fault momentarily. Back in the early Noughties, I can remember going on an Audi technical course where it was mentioned that they were looking into upgrading the electrical system on future A8's to a higher voltage (24v I think) to cope with the increasing electrical consumption, but obviously never did it. With the even higher consumption on new cars that wasn't there even then, I do wonder how long before they start thinking about it again.

[Envy]

3 hours ago, Beezil said:

I would concur with this. There is so mu h load on the electrical system these days that it's possible to get minor current drops which will be enough to flag a fault momentarily. Back in the early Noughties, I can remember going on an Audi technical course where it was mentioned that they were looking into upgrading the electrical system on future A8's to a higher voltage (24v I think) to cope with the increasing electrical consumption, but obviously never did it. With the even higher consumption on new cars that wasn't there even then, I do wonder how long before they start thinking about it again.

I have heard that the next gen Hybrids will be 48VDC - 

[SirTT]

The new A8 is 48v as will all future Audi's also be.