Battery Flat in 2 Days

[johngun1]

Hi Guys,

I'm running a C220CDI 2001. If I park it over the weekend despite the fact that its had a good run on the Friday, by Monday morning the battery is flat.

Now before you all say "its the battery" let me say been there n done that, fitted a new battery and hey presto it was flat the following Monday morning. I've borrowed a clamp on ammeter and with everything switched off its showing a varying current of between 0.9 and 3 amps flowing. It just goes up and down at random. I've gone through the 3 fuse boxes removing one fuse at a time but none of them made any difference. My simple maths tells me an average of 2 amps X 60 hours = 120 amps, the battery has a 100 amphour capacity, ergo flat batt.

One thing I did notice is that there are two positive leads from the battery terminal, one goes across behind the engine and dissapears, the other goes into a black box with a square red flap type cover with a + on it. Under the cover there is what looks like a metal link?? Anyway what I noticed was that it was the cable going to this black box that had the current flowing.

I'm guessing that the other cable goes to the Starter and this other one supplys everything else. So as none of the fused circuits appear to be involved, I'm coming to the conclusion that it may be an earth leakage through the Alternator.

Anyone got any experience of anything like this? or do I put myself at the mercy of my local MB stealer!!

Cheers

johngun1

 

[television]

You can always unplug the wires from the regulator pack on the alternator

 

[carabind]

You've done the clever thing which is to try and confirm/isolate the leaking current with a meter, and have done well to fnd a discharge of 1-3 amps which is the cause. As Malcolm says, if you can get to the alterntaor, why not disconect it (there should be a plug at the back) ?
If the drain remains, at least you have eliminated this. There will always be a small drain for memorys , alarm/immobilsers etc, but nowhere near 1-3 amps! How long has this be going on, I take it you've not just fitted a new bit of kit like a radio/alarm that may have a power hungry memory!!

 

[OmniCognateNeutronRangler]

oddly this was exactly what was happening with the rental Vectra I had last week. Turned out on that it was the trip computer thingy had a short. However, the AA man said a drain of 1.5 amps is typically a bulb. He tried unpluggin any that he could and checking every one was definately going out. He also removed the fuses for any of the lighting circuits to see if it was still draining.

Basicallly if you are a member, call the AA and he should keep digging until he finds what causing the drain. Alternatively, pull fuses until the drain stops registering and at least then you'll have a better idea of where it's coming from.

 

[type49]

Your drain should be about 0.05amps. Rear SAM units do play up. Also check for any signs of water leaks, check carpets etc as CAN lines run along sills & could keep units "awake".

 

[Uncle Benz]

Sounds like you could be on the right track. From memory, I believe you are correct that that wire goes to starter and then on to alternator. You will need to disconnect the large cable from the alternator to check for a fault with that unit. It is secured with a 13mm nut. By far the most common battery drain on 203 is with the seat control modules. There is one under each front seat, and you can check these by unplugging if the need arises. Your current clamp method is a good tip for others. When the battery is disconnected and reconnected, there are various items that come alive, giving a pretty impressive spark from the terminal. Some may mistake this for a heavy drain, but is quite normal on these cars.

 

[johngun1]

Hi Guys,

Thanks for the quick response. I've looked at the alternator, well the pulley and front plate, the rest of it is hidden. Looks like it needs to be attacked from below seeing as how I haven'tgot 14 joints in my arm.

The first time it happened was at Luton airport at 07:00, called the AA but all they were interested in was getting it started an checking that it was charging.

Guess I'll get it on the ramps and see if I can get at the alternator from below.

Thanks for your help, Ill let you know what I find.

Cheers

johngun1

 

[television]

You may be able to get your clamp meter near the alternator

 

[mattkh]

Hi

What is a clamp on ammeter.
How do they work.
Where can i buy one?

 

[television]

They are simple to put onto the cables, like a padlock in a way, good ones that measure down to milliampers DC are expensive

http://cpc.farnell.com/jsp/search/r...2908&Ns=PLS_NIC_FLAG|0||PLS_MAN_PART_NUM|0&D=

 

[panason1c]

Have you checked that the boot interior light is not staying on after the boot is closed?.........that would drain a battery within a day or two...

 

[greenfingers]

The most common cause of a battery drain is aftermarket equipment.
Do you have any non standard electrical stuff fitted? Stereo, DVD, SatNav, towbar electrics, hands free kit, etc.
Any of these may draw a small current when the ignition is off, but if you have a drain of more than about .2Amps, then something is wrong.

I had a nightmare with a VW Sharan which had loads of extra gadgets - tried new batteries, pulled fuses, disconnected alternator and so on, but every morning the voltage had dropped .4Volts.

The current may take a while to stabilize after switching off the ignition. The engine electrics do not shut off instantly, so be sure to wait a while until you are sure you are measuring the 'resting' current.

The rectifier pack on the back of the alternator can draw a current back from the battery if it is faulty, so try disconnecting the alternator overnight, and compare the battery voltage the next morning (Remember that a colder temperature will give a slightly lower reading).

It sounds like you have tried pulling all the fuses, but if you still can't work it out, then go back and do it again noting down each one which makes a difference to the current, and remove every one until you get a zero reading.

If that fails, then you sure have got a nightmare on your hands!

 

[OmniCognateNeutronRangler]

The most common cause of a battery drain is aftermarket equipment.
Do you have any non standard electrical stuff fitted? Stereo, DVD, SatNav, towbar electrics, hands free kit, etc.
Any of these may draw a small current when the ignition is off, but if you have a drain of more than about .2Amps, then something is wrong.

I had a nightmare with a VW Sharan which had loads of extra gadgets - tried new batteries, pulled fuses, disconnected alternator and so on, but every morning the voltage had dropped .4Volts.

The current may take a while to stabilize after switching off the ignition. The engine electrics do not shut off instantly, so be sure to wait a while until you are sure you are measuring the 'resting' current.

The rectifier pack on the back of the alternator can draw a current back from the battery if it is faulty, so try disconnecting the alternator overnight, and compare the battery voltage the next morning (Remember that a colder temperature will give a slightly lower reading).

It sounds like you have tried pulling all the fuses, but if you still can't work it out, then go back and do it again noting down each one which makes a difference to the current, and remove every one until you get a zero reading.

If that fails, then you sure have got a nightmare on your hands!

this is exactly what the AA man did with my rental wreck.

 

[turnipsock]

I had a faulty central locking pump, mainly because it was sitting in some water.

 

[Steve Taxi]

Battery Drain

I have exactly the same problem on the same model car, can the original poster let me know what it turned out to be please.

 

[robbo]

Do you have memory seats?

 

[Steve Taxi]

Battery

No just manual electric, the drain is .85 amps with a clip on ammeter and I tried removing fuses, no luck

 

[television]

You could unplug the cables from the alternator and test