C Class 2004 Diesel Rapid Battery Drain

[ellisr]

I parked my C Class on Xmas Eve, returned Boxing day to find the battery was totally flat. I thought I may have left the tailgate slightly open so assumed the load space area lights had caused the damage. I jumped started the car drove for about ten miles and returned the car to to driveway. The battery again went flat, I removed the battery to recharge, replaced the car started fine, took it to my local garage where they checked the battery and whether the car was charging, both okay. 3 / 4 hours later I went to the car again the battery was flat. To eliminate the battery my local garage loaned me a battery this I fitted to the car, 3 /4 hours later the battery was again flat.

The only clue given by the on-board computer to the cause, the first time the battery went flat a message appeared on the dash, 'Malfunction 1 light sensor go to workshop' or words to that effect.

Has anyone had a similar experience? What is the cure?

 

[Uncle Benz]

Do you have electric front seats? It's by no means the only one, but the seat controller is a very common cause of battery drain. You can reach under the front seats and pull the plugs out to see if it is. Black box, roughly six by four inches, half inch thick, three plugs from memory. Unplug and see if problem goes. Plug one seat back in to identify which is faulty.

Other things I've seen, upper control panel with interior light, but less common.

 

[MERCSPORT]

I think I may have your answer -

From a personal review from a C320 -
The problem i had with my c class is that the battery kept draining over night, the main dealer said i needed a new battery and that would sort the problem, so i agreed at a cost of £200, the next morning i had a flat battery again, phoned the main dealer who were rude and didnt seem to want to know. So i conacted a specialist who came to my house and picked the car up, he found the problem within a few hours, the sat nav would turn itself on overnight and draining the battery, the sat nav was sent off for a repair and working perfect now and was a lot cheaper then going to the main dealer.

 

[television]

This short is quite bad, most controllers take a couple of days, not sure what engine this has, but one of the diesels gets a short circuit heat, the other thing that could flatten it quickly is the reg pack on the alternator

 

[Uncle Benz]

I have seen the seat controllers flatten the battery to nothing in three hours, Malcolm. I've seen probably ten of these in the last few years. There are plenty of other potential sources, but the seat controllers are so easy to check DIY I thought I'd mention it first.

 

[television]

I have seen the seat controllers flatten the battery to nothing in three hours, Malcolm. I've seen probably ten of these in the last few years. There are plenty of other potential sources, but the seat controllers are so easy to check DIY I thought I'd mention it first.

I agree that they can get bad, and they can draw what the fuse will allow, fair enough and easy to check with a fuse type ammeter

 

[umblecumbuz]

Oh yeah - and welcome to the forum Ellisr!

Baz

 

[ellisr]

I can see this will be a process of elimination:

I will check electric seats first as is the easiest, I have read about this fault but have not checked because I am sure the seats do not work unless ignition is on, unlike the example on You Tube.

No Sat Nav fitted so can not be that.

Upper control panel on interior light is a suspect due to the initial malfunction message; 'Light Sensor Fault'.

television, Short circuit heat; do you mean on the cylinder heaters?

This the first time I have used this forum so I hope I am following any protocol, forgive me if I am not. I am impressed by the number and quality of the responses, thank you all.

I will report back on progress

 

[television]

Some diesel cars have a block heater, there is an article in the diy section on this draining the battery

 

[turbopete]

given that the OP has a message on the dash mentioning a light sensor malfunction, could this possibly be related to the sensor for the interior lights and auto headlights? could tis sensor not cause a drain somewhere? (sorry ive no information on the circuit, but it seems a logical place to look!)

 

[Alex Crow]

Thoughts as above, the electric seats are the most common, but draining over night is very quick for that fault.
Do you have memory seats, with memory position buttons on the door/s?
If not, discount this fault.
If you do, there are fuses in the cockpit fusebox (driver's end of dash) that can isolate the drain to prove the fault.

Exactly what model is this?
If it is a 220/270 cdi then the heater booster is a likely suspect for an overnight battery drain, as Malcolm suggests.

 

[jonoace]

So that's another one on my list to check when he brings the car up next week for inspection

Regards Jon

 

[television]

I feel the same as Alex on this,,even a five amp drain from any controller ECU would produce smoke and a smell, though limited by the size of the fuse, most doors and seat have roughly 10 amp fuses, but these things are only ever intermittent operation, with that drain all the time as said it would smell and smoke

 

[Roxie]

The only thing that I have ever known to flatten batteries like this is if the glow plug timer sticks in. If you still have the problem unplug it as a trial.

 

[ellisr]

Malcolm / television wins the prize for correct diagnosis!

Some diesel cars have a block heater, there is an article in the diy section on this draining the battery

I searched for information on block heater via internet, also Haynes manual couldn't find reference to block heater anywhere. My local garage couldn't find the problem (and I really rate the two guys there), so it was of to the Mercedes dealer. The verdict as explained to me, coolant heater gone wrong causing 20 amp drain when car was at rest. To be fair to the dealer the service was good but boy was it expensive!:Oops: If I could find out where this coolant / block heater was on the car I would tell you all where to look but after my internet research and repair manual search I still don't know where it is. Anyway for those with a flat battery when they have checked all the obvious find out where this thing is and see if you can get it checked by someone other then the Mercedes dealer.

Thank you to television for the correct answer and to everyone else's input.

 

[television]

I searched for information on block heater via internet, also Haynes manual couldn't find reference to block heater anywhere. My local garage couldn't find the problem (and I really rate the two guys there), so it was of to the Mercedes dealer. The verdict as explained to me, coolant heater gone wrong causing 20 amp drain when car was at rest. To be fair to the dealer the service was good but boy was it expensive!:Oops: If I could find out where this coolant / block heater was on the car I would tell you all where to look but after my internet research and repair manual search I still don't know where it is. Anyway for those with a flat battery when they have checked all the obvious find out where this thing is and see if you can get it checked by someone other then the Mercedes dealer.

Thank you to television for the correct answer and to everyone else's input.

Thank you you have made my bad day into something to live for.

It had to be that for any electrics to pull so much current there would have been smoke and a smell

 

[Alex Crow]

For the record, on most Mercedes Cdi cars it is mounted on the engine block above the starter, and not unusual to cause a heavy battery drain when failing.

 

[sadeghMB]

Battery Drain Problem

Hi guys
I am new in this forum and I know this discussion is for few months ago. but anyone can help me I appreciate it. I have the same problem of battery drain. I have done some of the things others mentioned in previous posts but no improvement. I have done one more test and I don't know what the result means. I removed the negative wire from battery terminal and when I touched the negative terminal on the battery with lead of a multimeter and body of the car "ground" with other lead, it shows V12. whereas I am not touching the posetive terminal at all. dose it mean that there is a short current circle? TQ

 

[television]

Welcome, the ammeter must be connected in series with any lead from the battery and the meter must be set to the highest DC current range, you then read it off after the car has gone to sleep

 

[sadeghMB]

Thanks for your reply, I did the same thing for the meter and also I waited for about 5min for sleep mode,I'm not quite sure how long it takes to go into the sleep mode. however, I even test it with a tail lamp 1156 12V25W. I mean negative side of the lamp to the negative terminal of the battery and posetive side of the lamp to the car's body. It was able to turn on the lamp. what do you think?