Just a suggestion, Check the fusebox in the passenger's footwell for water damage. You'll need to pull back the carpet from the front & you should see the fuse box & secondary battery.

It may not be down to the condensation though, if your carpets are wet then it could easily be a water leak from the rear vents with the water tracking down the sill & floorpan

Good luck in sorting it out

 

Thanks David.

pulled carpet back and it's dry. Just had same thing happen again at another traffic lights... Message on dash reads... Without changing gear consult workshop...

Have noticed that the stop start button becomes inactive.. Also when it was active and the stop start kicked in I manually took it off to start the engine and the radio flickers on and off.

It had the main battery changed 1 year ago. I am wondering if I need to get a new auxiliary battery or prob just best getting it on the mercedes diagnostic before spending on stuff that could be fine?

 

There is more than one thread about water in the footwell of W176 A-Class, in case it was more than just wet feet.

Rain water in footwell

I noticed water in the footwell in the back passengers seats, I thought I had left the window or door hoovered with a vax machine to collect all the water, covered the car and the next morning water again in the footwell. Is this a fault with the A180 class I have took the car to MB independent...

www.aclassclub.co.uk

In terms of the start/stop that probably is down to the current colder weather. After your stop the car probably needed to top up the battery.

I'm sure others will respond to the other glitches.

 

Update on this one. Took car in to independent dealer for diagnostics. Fault cause caused by auxiliary battery issues. New auxiliary battery fitted. Car did not mention anything about low auxiliary battery. Just the issue with the error code. Hopefully will help someone going forward with the same problem 👍

 

Good to hear it's fixed. And straight forward as well.