A3 start/ stop function

[Alan from Bury]

I have a 74 plate Audi A3 bought brand new in September 2024.

The engine start / stop function is not working. I have done a fair bit of urban driving recently but on Friday I undertook a 60 mile round trip on motorways so expected it to kick in, especially in the hot temperatures.

The function is switched on so don't understand why it is not working. A trip to my local dealer required?

[Magnet]

Hello Alan,

We all have varying opinions on the pos and cons of Stop/Start systems - as you will see via. a forum search.

Straight talking personal opinion:-

If I were you I would be clapping my hands that this engineeringly averse system isn’t working. 
If your views differ on the environmental benefits, then it might be worth considering the never-mentioned hundreds of thousands of tonnes of low grade fuel burnt in the atmosphere by aircraft every day. 
If you want it working ‘because it’s fitted and so it should be woking’, then the answer lies in using the car fa more frequently - which is of course environmentally averse! 
Our non-Audi behaves like yours because it can sit for a couple of weeks without use, prior to a 180 mile round trip - after which it occasionally wakes up, and I have to remember to isolate it!

Yes, you can take it to the dealer Alan, and have some funds extracted from your wallet, and then discuss the possibility of them fitting a new battery (possibly at you expense), but I believe the answer lies in ‘fair bit of urban driving’.

Regards,

Gareth. 

[Alan from Bury]

I will see how it goes for a few days but after that would expect the dealer to give me a FOC solution given I have only done approx 3000 miles.

[Steve Q]

Keep us posted on how you get on. 

[cliffcoggin]

My wife's Yeti has the stop/start system which I surmise from watching its operation works as follows.

The stop/start control constantly measures the battery voltage when the engine is stopped to ensure there is enough power left to restart the engine. Urban driving involving many stops/starts without enough time between stops to fully recharge the battery will be sensed by the control which then prevents engine stops when stationary. Add to this the load imposed by the AC system in hot weather and stops may not happen at all.

All of this requires a special kind of battery (AGM) which needs to be in tip top condition for the function to work. That's why one of the first symptoms of a failing battery is that the stop/start system does not engage.

Personally I am undecided if the system is worthwhile if you take the wider view of the overall impact on the environment. Does the fuel and emission saving balance the extra wear on starter motors and batteries which then require replacement using more materials and energy? I don't know because I can not quantify the two sides of the equation, and as a scientist at heart verifiable facts are important to me.