daicochlin

I have a C200 CDI coupe and last week it decided not to allow me in. I found the battery to be so flat that i couldn't even open the door. I jump started it and got it home. following morning the same. I replaced the battery and drove it about 10 miles all seemed ok. 4 hours later went to open it exactly the same. AA man rescued me and informed me of a 14amp drain on my battery.. Anyone have any ideas what would cause this???

mrbobby

Wow that's quite a drain. I'd start checking all the large diameter cables. It would have to be a large cable to handle that amperage.

triffer

My A.A. man not only got my car unlocked no emergency key started the car found the fault fixed it and been sound ever scince
right cant remember exact drain he said 14 34 amp but it was constant and a common problem on the diesels this guy was top gave him a £10 to get a drink anyhow the problem was the heater asssist on the engine warms water in radator quicker the relay stick on.... its located above the starter motor i used my phone on record to see it when i had starter motor trouble but dont have the vid any more he disconnected the live wire and taped it off pain to do but can be done with care as its on top of the starter motor and needs to be axcessed from underneith sorry about the spelling hope it helps....just seen date sorry late replie

Garticus

You'd possbly have to put a clamp meter on the battery cable (to sense the draw) and start pulling & reinstalling the fuses until the draw disappears.

When/if the draw disappears when a certain fuse is pulled then there's your faulty component/system.

Diesel Benz

Is it a W203? Could be the electric heater booster. Those are prone to fail and the current could be much higher than 14 A if more than one of the parallel heating circuits are misbehaving. Note that pulling any of the ordinary fuses does not help in this case.