2006 vauxhall astra keeps having battery drained and wont start

Question

Hi i bought an 06 astra in october and since then its had 4 batteries and a new alternator but it still dies over night. I was told potentially the radio was draining it and that was a knows fault. I had the radio unplugged and the car ran fine for 2 weeks but has died again. What else could it be anyone know? Im thinking starter motor.

When its died it unlocks with key remote and the clock still works but when i try to start it it just ticks over but is fine again after a jumpstart. Ive soent a fortune on it so thought id ask here

Answer 1

I would try using a multimeter that can measure DC current to see which circuits are drawing power with the ignition off. The radio should draw some, and the alarm (if your car has one) and whatever circuit handles the remote door locks, but other than that there shouldn't be anything drawing any power. Make sure there aren't any lights or anything that aren't shutting off, possibly a boot or bonnet light switch has failed and those lights are always on.

If you strongly suspect the starter, you should be able to pull the fuse for it before you go inside for the night. If the car starts in the morning (after you replace the fuse, of course!) then it may be you've found your culprit.

Answer 2

Have the charging system load tested and make sure the battery is fully charged 12.5v or better.

I'd avoid disconnecting parts or pulling fuses until you can identify the source of the draw. There are too many computers and circuits that stay active when you turn off the ignition.

If you have a multimeter voltage drop test the fuses by placing the leads across the exposed terminals of the fuse.

A link to a millivolt to milliamp chart

Generally when doing a voltage drop test you'll want to have the doors open so you can access the interior fuse boxes. Depending on what type of door switch you have you can either flip the door latch to the closed position or if you have the plunger style switch gain access to the connector and jump the two pins. You also want to wait for at least an hour to make sure computers are asleep and any circuits have shutdown before doing any parasitic drain voltage drop testing.