CLA 180 (YOM 2017) - battery draining issue since last service!
 

Today I took my CLA 180 (YOM 2017) for servicing and they said that the car battery seems to be faulty and the CEL appears. My car only has ~16000 KMs on it and I never saw any signs of a dying battery! So I believe that they messed up something during servicing and now trying to put the blame on the battery. I refused to agree with what they say about the faulty battery. Then they told me that they may have accidentally kept the ignition on and told me to keep the engine running and that might fix the issue by re-charging the battery.

I kept the engine running for about 3 hours! And then I turned it off and try to start up after about 30 minutes the car won't start and the battery seems to be dead :(

People who did the service work said that they cleaned up the windshield washer tank and they had to remove the front bumper to get to it. However, by looking at how they tried to diagnose the battery issue, I got the feeling that these guys don't have a good sense of what they are doing. I'm taking the car back to the dealer tomorrow.

Any tips on where to look would be much appreciated as I can pass them to the mechanic doing the diagnosis.