What is draining the battery? Any ideas?

[m7m]

Normally my 13-year old E200 works fine, but leaving it for a few days cause it not to start. After leaving it for a week, there were not even lights on the dashboard.
Breakdown service tested battery, and it is healthy and charging correctly.
Front passenger window not working, but it may not be related (Don't usually use the window. Hence, no idea when it died).

 

[nigel cross]

Have you tried connecting an ampmeter?
If there is a drain it show a discharge.
Then start pulling fuses till it stops

 

[Benzowner]

Quite often caused by a light on in the boot, glove box,

 

[kole301]

Yes... In my case the problem was the switch of the light of the boot...

 

[m7m]

Thanks for the replies.
I tested the boot light. It is working correctly. i.e. it swithches off when the boot lid is closed.
As for the glove comparment light, it does not come on at all.

The ideaq of using an ameter to measure the drainig on the battery is great, but I do not have one and shall investigate the cost. It is worth investing in one.
However, I don't know what level of draining on the battery is allowed (since power is needed to power the alarm system, clock, ..etc)????

 

[tsktsk]

Check the bolts holding the boot lock in position, as it may be that the lock mechanism is sometimes moving slightly when it's closed. It happened on mine intermittently, and one some occasions the lock would engage but the lid would not close enough for the light switch to depress fully. The battery drained overnight.

 

[Stratman]

If you're confident using a multimeter and also pulling fuses, the way to positively identify the circuit at fault is as follows.

Buy a multimeter (Maplins is a good place to go) and set it up to read DC Amps up to 10A or whatever the high range on the meter is. Disconnect the earth lead from the battery and connect the meter in series with it, meter Positive lead to the battery, Negative lead to the car's earth wire. The meter should now be reading the leakage current. If it's too low to register switch the meter to the next-highest range (maybe 1 or 2 amps?) and keep going until you get a decent reading.

Anything more than about 50mA (50 milliamps, 0.05 amps) is not a good sign. Open the fusebox cover and one by one pull (and replace) the fuses until you find which circuit is causing the leak. You'll then know which components are suspect.


UT30B looks OK

 

[jaymanek]

These are handy

AUTOMOTIVE CURRENT AMMETER TESTER, CAR DIAGNOSTICS, NEW on eBay (end time 18-Apr-10 22:23:59 BST)

 

[nigel cross]

Check the bolts holding the boot lock in position, as it may be that the lock mechanism is sometimes moving slightly when it's closed. It happened on mine intermittently, and one some occasions the lock would engage but the lid would not close enough for the light switch to depress fully. The battery drained overnight.

If you want to prove it either way, is to remove the bulb, the it cant come on and drain the battery.
It will prove it either way and so narrow down your search

 

[m7m]

Am I right to assume that it is possible to use an ameter that clips on the battery wire and measure the current using magnetic filed?
Will it do the job?

 

[pmcgsmurf]

Am I right to assume that it is possible to use an ameter that clips on the battery wire and measure the current using magnetic filed?
Will it do the job?

That would be a clamp meter, usually costs more than a cheap little multimeter to do the job.

 

[Diesel Benz]

That would be a clamp meter, usually costs more than a cheap little multimeter to do the job.

Also clamp meters usually are for higher currents and may not be accurate enough for quiescent current measurements. But there are a few that are accurate at very low currents, these are very handy when finding leaks. Too expensive to buy for diagnosing one car, in my opinion.