My Mercedes C Class runs battery down while parked

[tamoshanter]

I bought brand new battery and put it into the car, didnt drive the car for 3 weeks as use a company car and was away from home for about week and half. When i went to take the car for a drive and enjoy her, the battery was as dead as dodo. Got battery replaced and have now taken to leaving the battery not connected/removing the terminals. As i said i rarely use the car

When i connect the teminals one of the them (live one) sparks a lot and unless the terminals are very tightly screwed it wont start


Any ideas please as i am at my wits end. Thank you

 

[telectrix]

if it sparks when connecting, then something is drawing current. a small current is normal. modern cars have ECUs, central locking, all pull a bit. try measuring the current drawn when everything is switched off. if , for example, it's 1Amp, then your battery will run flat in about 80 hours.

 

[tamoshanter]

if it sparks when connecting, then something is drawing current. a small current is normal. modern cars have ECUs, central locking, all pull a bit. try measuring the current drawn when everything is switched off. if , for example, it's 1Amp, then your battery will run flat in about 80 hours.

Thanks for your reply. How do i do this. Sorry but im a total newbie to this :shame: Off the top of your head is there something that comes to mmind as most likely culprit. Someone had suggested disconnecting the heater on the engine. The car is a C250 Turbodiesel you see and apparently they have a heater next to engine for the engine/fuel

 

[ruston]

And the battery may not have been fully charged when you bought it. Modern cars will draw current while standing , and need a good reserve of power to start the engine.

 

[tamoshanter]

And the battery may not have been fully charged when you bought it. Modern cars will draw current while standing , and need a good reserve of power to start the engine.

The battery was brand new. When i bought it and put it into the car i actually drove it for some distance and started up fine and stuff before i left it parked for the period in question. The battery before that had to died rather prematurely too but i put it down to repeated cranking/starts as we were fixing the car during repairs

 

[Earthstore]

Do you have a multi meter?

 

[tamoshanter]

Do you have a multi meter?

I actually have to google to see what that is

 

[telectrix]

If you're going to leave the car for 3 weeks standing, then it will go flat.

 

[Earthstore]

I actually have to google to see what that is

Oh.... You will need to take it to a garage or an autoelectrician then, it sounds like you do have something draining it, the tests are quite simple but you do need some knowledge of how to test..

Also your terminal will spark when connecting if the inside light is on in the car, IE the door is open.

I hope this helps.

 

[dan86]

Personally, if I was you I'd be tempted to get a trickle charger and stick that on it when it's not in use. I have a lot of customers that do this on classic cars, bikes, 2nd or 3rd cars they don't use very often.
By all means take it to a decent garage that can test the charging system etc, but I don't think you will find anything wrong with the car itself.

 

[telectrix]

apart from it being a rust bucket merc.

 

[dan86]

I was being polite!

 

[Darkwood]

Clamp meter and remove fuses and see when the current virtually disappears, i had this on my astra and it was the diode pack on the alternator ... it was drawing 60amps with engine off ... if ou crash the battery down to zero charge you may damage it so get a garage to do a load drop test on any battery affected see if its damaged beyond usefulness.

 

[dean.diy]

yes, feel's like something's drawing current whilst on the driveway AND the loose terminal's worth another look.

 

[ruston]

If you have a lose battery terminal the starter will not be able to draw the load required to start the car , the alternator may not get the full charge either, so you will always be on your back foot.

 

[tamoshanter]

Oh.... You will need to take it to a garage or an autoelectrician then, it sounds like you do have something draining it, the tests are quite simple but you do need some knowledge of how to test..

Also your terminal will spark when connecting if the inside light is on in the car, IE the door is open.

I hope this helps.

So is this potentially an easy fix for a garage or auto electrician

 

[dan86]

a decent garage will have it checked out in no time.

 

[ruston]

As above.

 

[Earthstore]

Ditto above.

 

[guest119]

There is a way to bring the battery back from way down zero, if you need to.

Boydy

 

[tamoshanter]

There is a way to bring the battery back from way down zero, if you need to.

Boydy

how aprt from charging it :ninja:

 

[militar veteran]

Leaky diode in the alternator can cause this,try replacing it and check the belt tension to ensure proper charging.

 

[gnuuser]

how aprt from charging it :ninja:

first you need to test the electrolyte in the battery if it has the proper specific gravity and density then a low current (2 amp) charge over a period of a week should restore it.
your mechanic can do this for you
I always have a spare battery on hand in my garage

 

[guest119]

Charge in series with a load.
Something like a headlamp capsule ( phew, nearly said bulb!).
Same was as repairing power tools batteries, except L-ion.

Boydy

 

[solarsavings]

I made the mistake of buying c class cdi some years back and got rid of it as soon as the warranty ran out. While we had it would suddenly accelerate of its own accord, needed naff sensors. Expensive to have serviced and not great to drive.

About six months after we part exchanged it the new owner rang to ask if there had been any electrical faults as it kept draining the battery and had £3500 in warranty work done and it still wasn't fixed.

The only thing we had noticed just prior to selling a ticking from the speakers while the radio was off. We also realised that merc main dealers only employ part changers so my advice is don't take it to one of them.

 

[guest119]

I bought a 220cdi estate in 2007, a 52 plate, 140k, nearly 7 grand.
18 months later 169k, rotten round the rear arches, rear hatch, around the screen etc.
Multiple injector faults (£lenty).
Went out one morning and it wouldnt change up past 2nd. Merc said bring it in, pay for plug in and we will tell you what MIGHT be wrong with it. £control module this £control module that??????
So, onto e -blag ............£1500.
Won by a couple of Turkish lads in London who drove up for it and took it round the corner, phoned the AA (relay) and got it home.
I suspect they were breakers.
Pile of ----, never again.
Boydy

 

[tamoshanter]

Is this gadget any good for a battery draw test?

AUTOMOTIVE CURRENT TESTER - CF-02S

 

[gnuuser]

Is this gadget any good for a battery draw test?

AUTOMOTIVE CURRENT TESTER - CF-02S

it may test and read the current but i dont know if it will apply enough load to accurately guage the battery.

I have a load tester in my garage (an old one)
while it reads the current of both the charging system and battery under load test it draws a heavy current amout
(approximately 60 to 80 amp) and will rapidly tell if a battery if failing
if you dont have one its better to take it to a garage and having it tested.

 

[Octopus]

Is this gadget any good for a battery draw test?

AUTOMOTIVE CURRENT TESTER - CF-02S

What you need to buy is a trickle charger. My brother in law has one for his "occassional" car to stop the battery going flat

 

[gnuuser]

What you need to buy is a trickle charger. My brother in law has one for his "occassional" car to stop the battery going flat

murdoch is correct
a trickle charger will do the trick by keeping a maintenance charge going when needed
this will help a lot when the car isnt being used for a while

 

[telectrix]

best place for a merc C class:

 

[PEG]

Mercs rep has gone in the last 15 years,only ones worth having are G Wagens,large commercials and very top of range. I remember a technician at Portmans telling me the ML's were sometimes just unfixable electrically. Just like the tide of blinged up £90,000 Rangerovers i happen upon,with faults you'd never get on a 20 year old Mk 1 escort...it must be Ms Merkel scowls so...:coolgleamA: