Electrical current drain

sib8292 · Dec 9, 2007

I had a problem recently on my daily use S2. The (year old high power)battery seemed to be losing charge. The car got sluggish turning over first thing, and in cold weather really slow. Then one Monday morning the battery was flat.

Having called out a local mobile elec engineer he ran a test on the battery and alternator and confirmed they were fine. Fault was then traced to a glove compartment light switch that was not switching off when the glove compartment was closed. Not visible of course; so current waas draining continuoulsy and in the winter weather not recharging sufficiently.

Temp fix was to remove bulb and a new switch has to be fitted.

So if you have similar symptoms try this.

peanut · Dec 9, 2007

usefull tip thanks
Lucky you called a sparks otherwise you would probably have had to fork out for a new battery un -necessarily and still not found the source of the problem.

zcacogp · Dec 10, 2007

Using an ammeter in series with the battery when the car is turned off can be a useful diagnostic. It shows how much current drain the battery is subjected to - often more than you'd imagine.

Alarms are a common culprit. Or electrical failure (as you found.) Or (in a friends' case) a CD changer on an old head unit seemed to want > 300mA for doing nothing at all ... on an old 928.

Oli.

xenon · Dec 10, 2007

True. But remove the series-connected ammeter before cranking the engine, won't you?

My mate didn't and he had to buy a new meter, surprise, surprise. He also needed a new fire extinguisher and a new pair of kex. [&:]