Recurring battery failure

[Martin Connolly]

Just before Christmas, my C320 refused to start one morning. I called recovery and the engineer said the battery was flat (even though it had started at 10pm the night before). The local dealer said the rear SAM was faulty and replaced it, as well as the battery. All works fine for three weeks, then this morning the battery was flat again. I charged it and it started, then two hours later it was flat again. Later that night, the damn alarm keeps sounding (I guess as the battery runs out), and the only way to stop it is to keep it connected to a battery charger all the time (I tried disconnecting the battery and it doesn't work!).

So, two questions (if anyone can help me):

1 - is the replacement battery duff, or is something else draining it?
2 - is there any way to stop the damn alarm from sounding all night when the battery goes flat? Surely, there must be some way to disconnect it?

 

[mlc]

Martin,

Cant help with the alarm. Getting a duff battery would be very unlucky but if you run the car into your local trustworthy tyre / exhaust / battery specailist they will check the battery / alternator in two minutes for free. As for the power drain the most common thing is a boot light that stays on, this was a suprisingly common fault when I worked for the AA. im not sure if the back seats fold on your car, if they do fold a seat, close the boot and look through to see if the boot is lit. If not see if the bulb is warm when the boot has been closed

Hope this helps.
Mark