Mercedes ML W164 Battery Drain

220Apc

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Hi.

I have a Mercedes ML320 W164, I have had 3 new batteries over the last 12-months thinking it was the battery, I am experiencing battery drain over 3 / 4 days which it nearly flattens the battery completely, I also know someone else who is experiencing the same problem also on a W164. Any ideas where to look to solve the problem would be greatly appreciated.
 

Bobby Dazzler

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I don’t suppose you have a rear parking camera do you?

I had a battery drain on a W164 and afterwards the camera control module was dead. The dealer said it was probably the cause rather than a consequence.
 
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220Apc

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Hi
I don’t suppose you have a rear parking camera do you?

I had a battery drain on a W164 and afterwards the camera control module was dead. The dealer said it was probably the cause rather than a consequence.
Thanks for your reply, no I haven’t got a rear camera, thanks anyway, the search continues👍
 

Bobby Dazzler

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Do you have anything plugged in to the OBDII port - this can be found underneath the dashboard beneath the steering wheel.

The OBDII port is always live and so if something is plugged into then there is a risk that it will flatten the battery if not disconnected.

Alterntaiveky do you have any accessories plugged into the 12v sockets, eg dashcam, satnav, USB socket, etc?

Most 12v sockets will switch on/off with the ignition, but some people do require them to be permanently live for dashcams, charging, etc.
 

Tezz

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Are all you door locks working ok 100% all of the time, especially the tail gate
 
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220Apc

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Do you have anything plugged in to the OBDII port - this can be found underneath the dashboard beneath the steering wheel.

The OBDII port is always live and so if something is plugged into then there is a risk that it will flatten the battery if not disconnected.

Alterntaiveky do you have any accessories plugged into the 12v sockets, eg dashcam, satnav, USB socket, etc?

Most 12v sockets will switch on/off with the ignition, but some people do require them to be permanently live for dashcams, charging, etc.
Hi thanks for responding, no nothing at all plugged in, the only thing that has been hardwired before I got the car is a Parrot handsfree kit, but it does go off on the ignition
 

Bobby Dazzler

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Do you know whether it’s on it’s original batteries? If it is then it won’t be a waste to replace them.

If you can charge the batteries using a battery charger or conditioner - plugged into the mains - then that might breathe a little more life into an old battery. That’s what I would do next.
 
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220Apc

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Do you know whether it’s on it’s original batteries? If it is then it won’t be a waste to replace them.

If you can charge the batteries using a battery charger or conditioner - plugged into the mains - then that might breathe a little more life into an old battery. That’s what I would do next.
Hi
Are you talking about the main battery or auxiliary battery? I have had 3 new main batteries but not the auxiliary battery

Thanks for your time 👍
 

Bobby Dazzler

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Hi
Are you talking about the main battery or auxiliary battery? I have had 3 new main batteries but not the auxiliary battery

Thanks for your time 👍
Someone further up this thread suggested that they had exactly the same issue and replacing the auxiliary batter fixed the issue.

What’s the reason you’ve had three main batteries, and over what time frame? It would not be unreasonable to expect a quality battery to last 5-8 years and so including the original you should have seen 20-32 years service from that many batteries!
 

Bert_W164

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Have you tested for resting current draw?
Is the aux battery in good condition?
Is the alternator in good condition, what's the charge voltage? Does the voltage fluctuate? Any gremlins with engine running?
Is your rear Sam okay?
Do you get any battery symbols pop up when driving?

Sorry for all the questions, but without establishing why it's draining you'll be going around in circles with a car that has a pretty sensitive electrical system as it is...
 
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220Apc

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Someone further up this thread suggested that they had exactly the same issue and replacing the auxiliary batter fixed the issue.

What’s the reason you’ve had three main batteries, and over what time frame? It would not be unreasonable to expect a quality battery to last 5-8 years and so including the original you should have seen 20-32 years service from that many batteries!
I bought the car approx 18m ago & the battery was replaced with a new one because it tested faulty, then approx 12m ago that was checked & faulty also, so I upgraded to a Bosch which I currently have, but it still flattens this one too, to the degree that when you put a meter across the battery it was down to 5v, I will start pulling fuses next to see what’s happening, alternator is charging ok @ 14.2v
 

Bobby Dazzler

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I bought the car approx 18m ago & the battery was replaced with a new one because it tested faulty, then approx 12m ago that was checked & faulty also, so I upgraded to a Bosch which I currently have, but it still flattens this one too, to the degree that when you put a meter across the battery it was down to 5v, I will start pulling fuses next to see what’s happening, alternator is charging ok @ 14.2v
I think I would be checking your alternator and charging system next. I had to replace the leisure batteries every year or two on my touring caravan. It turned out to be the charging system killing the batteries - it charged them but they were good for nothing in a year or so.
 

Major774

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I suggest confirming on bert’s first question.

Have you tested for key off resting current draw?
 
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220Apc

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I suggest confirming on bert’s first question.

Have you tested for key off resting current draw?Hi
Hi

Seems to be a drain of around 2.5A, someone I know had the same issue a couple of weeks ago, it turned out to be the drivers door lock sensor, so this will be a starting point for me aswell 👍
 

Jigglyjohnson

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Gain access to all fuse boxes before the current draw test is carried out and when the current draw has settled test the fuses in the fuse box one by one for voltage the one that is alive is the one causing the drain before you pull it out check the fuse sheet to check the consumer it feeds. Then pull the fuse and see if your current draw disappears
 
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220Apc

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Have you tested for resting current draw?
Is the aux battery in good condition?
Is the alternator in good condition, what's the charge voltage? Does the voltage fluctuate? Any gremlins with engine running?
Is your rear Sam okay?
Do you get any battery symbols pop up when driving?

Sorry for all the questions, but without establishing why it's draining you'll be going around in circles with a car that has a pretty sensitive electrical system as it is...
Current drain is around 2.5A
Garage said Aux Battery seems ok, ( I have not tested)
Alternator output 14.2v
It does fluctuate slightly 14v - 14.2v
How do I check the rear SAM please?
No other issues while driving, but it did throw a wobble once a couple of months ago but only once never again, the power drain was massive as it cut the Bluetooth car kit out, nothing electrical seemed to work, but no issues since.
 

Jigglyjohnson

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Best way to test which consumer is at faults is as I described above set the drain measurement so you have 2.5 amps which is far to high should be about 0.06 max then get another multimeter and check each fuse for a current reading
 

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