battery draining w124 e220

[squareonemark]

Afternoon chaps,

I'm at my whits end and am looking for some help.

I've a previously very reliable 1995 e220 w124 with 135k on the clock with what i reckon must be an intermittent fault which is causing the battery to run completely flat.

The history is as follows - During the cold snap my battery went totally dead - had to get into the car by going through the boot. I've since bought a new battery and my garage has tested the alternator and all seemed fine.

However a couple of days after the new battery was fitted the battery went totally flat - meaning i had to get in through the boot again. It's been back into the garage where their electrics guy gave it a once over and couldn't find any fault.

It's not the vacuum pump for the doors and as far as i can tell the retro fitted alarm isn't connected anymore.

I've had a look through the forum at various other posts but there doesn't seem to be any solid answers to this type of problem - if indeed there is a solid answer!?!

Anyone got any ideas? I'm at a loss.

cheers,
Mark.

 

[kth286]

you can get a clip-on ammeter from sealey and clip it around the battery cable and then pull each fuse out of it's holder in turn to see which circuit is causing the problem.

the chart will then tell you what items are on the circuit.

 

[squareonemark]

Many thanks David.

I'm guessing that if it it is an intermittent fault the only way to get to the bottom of it is to have the tools to do it yourself so you can keep checking the fuses on a regular basis?

I suppose there is the possibility that the auto electric guy may have been looking at the car when the fault wasn't present? (crosses fingers)

Cheers,
Mark

 

[television]

The only thing that I can think of is the reg pack short circuit,,there are no memory things on this car to my knowledge, and that is some drain that you have there

 

[grober]

Its been known that the boot inside light switch goes faulty permitting the boot light to stay on with the boor lid shut thus draining the battery. Quick test is to remove the bulb. Otherwise is to remove fuses one at a time to isolate the battery current drain-assuming its a fused circuit? If the alternator rectifier pack has gone short circuit this will rapidly drain a battery since its unfused. The other possibility is the alternator is not charging- did your garage guy check this. On older cars shorts to earth usually occur where wiring is bent or goes thro a metal orifice-best example is the wiring in the door hinges.

 

[squareonemark]

cheers guys.

Television - I'll take a look for info on reg pack short circuit. there aren't any memory things on this w124 a far as i can tell.

Yes it is a pretty big drain on the battery - it can kill it stone dead in a matter of hours. when you consider that i'm leaving no lights on - interior or exterior - it's one big damn puzzler.

Grober - I'm pretty sure it's not the interior lights as it's an estate and i'd be able to see if anything untoward was going on.

As soon as the clip-on ammeter arrives i'll be doing a fuse test. The very decent and reliable guy at my local garage checked the alternator and battery and says all seems to be as it should be.

My other concern is that the car has got quite damp inside over the years. It's not uncommon for the passenger footwell to have water slopping around in it. Another job that i'll be looking into over the coming weeks now i've a little more free time.

I've put in a request with television for the relevant info on another post regarding the drains etc.

Thanks for all your comments - your comments and suggestions are a real help!

Cheers,
Mark.

 

[television]

You need my water drain clearing paper,,I have sent out loads of them,,It is my best seller,,but it is free

 

[squareonemark]

just received it now - wish the postal service was that efficient - many thanks!

 

[television]

You do not need any test gear to find this if it is the alternator. Key out and everything turned off, disconnect the ground lead from the battery, as you have a short somewhere it will spark. Leave the wire off and take the wires off the alternator,,make sure that they cannot touch anything, touch the neg lead back on the battery,, no spark = fault found

 

[squareonemark]

update -

I'm still waiting for my ammeter to arrive so i've been unable to nail down the fault, however, it appears that the motor for the blowers may have gone as i can't get the blowers to work to demist the windscreen.

I've been disconnecting the neg. from the battery at night to stop it draining and i've noticed when i reconnect it there's been a spark on the neg terminal of the battery. Now, with the heater blower not working there's no spark.

I've checked the fuse for the blower and it's fine and when i connect the neg on the battery there's a little clicking/clunking sound.

Would this suggest i've stumbled upon the fault and i need a new motor for the blower or am i being hideously naive

Any thoughts?

 

[squareonemark]

Cars - you've got to love 'em!

The heater blower seems to be working again, so that would suggest an intermittent fault.

Does anyone think this fault would cause my battery to go flat so quickly?

 

[teddycatkin]

It would drain it if it came on whith the ign off of course---more than likely though a dodgy or corroded fuze is the problem there ( take em all out and clean them )?---check your glove box light is not on when the lid is closed too this will drain the batt without you knowing ?

 

[squareonemark]

just to follow up, I cleaned all fuses with cleaner and for good measure disconnected the fuse for the sun roof (not used - live in manchester) and all seems to now be working fine - since then the battery draining problem has disappeared - until tomorrow probably...

 

['89 250TD]

similiar fault on '89 250TD...

I tried removing the fuses after connecting a small 12v bulb between the negative battery post and earth (negative battery cable had been removed)

With the ignition off the test bulb lit until I removed fuse number 9 which is for the clock, emergency warning lights, interior light etc.

I disconnected door switches, bulbs etc but couldn't find what was the cause of the current drain

How can I find out if this is normal current drain for the clock or if its the cause of the battery going flat?

 

[Roxie]

If the battery can go flat in a few hours and the problem is intermittent then I would test the glow plug timer or disconnect it as a trial.

 

[television]

I tried removing the fuses after connecting a small 12v bulb between the negative battery post and earth (negative battery cable had been removed)

With the ignition off the test bulb lit until I removed fuse number 9 which is for the clock, emergency warning lights, interior light etc.

I disconnected door switches, bulbs etc but couldn't find what was the cause of the current drain

How can I find out if this is normal current drain for the clock or if its the cause of the battery going flat?

this is the circuit for your fuse number 9

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1990/300D/SYSTEM WIRING DIAGRAMS/3494.pdf

 

[Doug1234]

With one of the front doors open you will be able to operate windows or sunroof without the key in the ignition,,but when the doors are closed then you need the key in the ignition.

Check the windows / sunroof do not operate with doors shut and no ignition on,if they do go under bonnet and remove fuse box lid and then the 6 screws to completely remove the rest of the cover and check out the silver just over one inch square relay at the back of the compartment ,its the one that is involved in letting the windows etc work with no ignition ..this relay may be staying latched on and draining power.

Bit of a long shot and in theory it should not be possible to drain the battery down but it has a constant live source of power so who knows !!!