Hello there, can anyone please help? I have a clk that is acting very strange and wondered if you know what the problem is?

Quite recently I tackled some rust on the near side and whilst this work was taking place the battery accidently run flat! when I charged the battery it became clear that the battery wasn't holding charge so I invested in a new one. At the same time the driver and passenger windows would not go to the correct level when I opened the doors, they dropped down a couple of inches which inturn forced me to exit via the boot because the only way I could close the windows and exit was if I shut the windows and exit without opening either of the doors lol.

When I put the new battery in and started the car it sounded like it wasn't firing on all cylinders and the auto box was stuck in park. The fan runs also constantly and there are no lights on in dash at all.

Can anyone help please??????