Trouble Shooting Battery Drain with Radio?
Thread Starter
Super Member
Joined: Jun 2017
Posts: 577
Likes: 195
From: PA
W223 S500 LWB 4-Matic, W222 S450 LWB 4-Matic, A238 E400 Cabriolet 4-Matic
Trouble Shooting Battery Drain with Radio?
I started tracking down a main battery drain. Haven't put the amp meter to it yet, but discovered that these cars are notorious for the electric seat modules failing. So I temporarily disconnected those to see if that is the issue.
While I was in there I also noticed that even with the key fob out of the ignition (non-keyless GO) the Command 20 radio head unit is making a noise like it's trying to eject a CD. No CD is in the main head unit. I pushed the radio power button and to my surprise the radio turned on without the key in the ignition. The key hasn't been in the ignition for 24 hours.
Are these symptoms of another control modules failed causing excesses battery drain or should the radio work with the key out.
Something doesn't seem right there. Any ideas?
Thanks.
While I was in there I also noticed that even with the key fob out of the ignition (non-keyless GO) the Command 20 radio head unit is making a noise like it's trying to eject a CD. No CD is in the main head unit. I pushed the radio power button and to my surprise the radio turned on without the key in the ignition. The key hasn't been in the ignition for 24 hours.
Are these symptoms of another control modules failed causing excesses battery drain or should the radio work with the key out.
Something doesn't seem right there. Any ideas?
Thanks.
Thread Starter
Super Member
Joined: Jun 2017
Posts: 577
Likes: 195
From: PA
W223 S500 LWB 4-Matic, W222 S450 LWB 4-Matic, A238 E400 Cabriolet 4-Matic
Reading into it a bit more. The issue of the radio staying on is like opening a Pandora's Box. Some folks just gave up including MB $tealers... Bummer.
Possible causes:
CAN bus issue. Don't really have my head around that yet, other than it is a communications protocol between devices.
Rear SAM issue. A module in the back I presume?
Main battery relay issue. Somewhere near the main battery? Not disconnecting?
Command Radio head or DVD NAV unit issue. With the key out, mine keeps trying to eject a non-existent CD and a small pop is heard thru the speakers. Otherwise radio/cd NAV and 6 disk changer seam to work okay
SOS Unit. I believe you must go to the MB $tealer to get this disconnected/ turned off with STAR. I would think you could just disconnect it somewhere in the back of the wagon? Antenna module perhaps?
Alarm system issue. My siren and tilt sensor are disconnected via a connector dislodged at the rear fuse panel but the lights will still flash if the alarm is activated.
Not sure how to trouble shoot all these yet although I'll pull out the ampmeter for sure. Right now I have the new AGM battery charging up to start further testing later. I have the wagon up on jack stands awaiting front suspension parts with the Air compressor disconnected and removed. Probably should wait until i get the suspension & air compressor parts back together, then run a diagnostic too.
Possible causes:
CAN bus issue. Don't really have my head around that yet, other than it is a communications protocol between devices.
Rear SAM issue. A module in the back I presume?
Main battery relay issue. Somewhere near the main battery? Not disconnecting?
Command Radio head or DVD NAV unit issue. With the key out, mine keeps trying to eject a non-existent CD and a small pop is heard thru the speakers. Otherwise radio/cd NAV and 6 disk changer seam to work okay
SOS Unit. I believe you must go to the MB $tealer to get this disconnected/ turned off with STAR. I would think you could just disconnect it somewhere in the back of the wagon? Antenna module perhaps?
Alarm system issue. My siren and tilt sensor are disconnected via a connector dislodged at the rear fuse panel but the lights will still flash if the alarm is activated.
Not sure how to trouble shoot all these yet although I'll pull out the ampmeter for sure. Right now I have the new AGM battery charging up to start further testing later. I have the wagon up on jack stands awaiting front suspension parts with the Air compressor disconnected and removed. Probably should wait until i get the suspension & air compressor parts back together, then run a diagnostic too.
Last edited by Sleeper Benz; Jun 14, 2017 at 11:57 AM.
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Joined: Sep 2017
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From: Germany Leipzig
A-Class W169
Mine does, some A20 in a W169.
It switches off with Ignition switch all off position, but you can switch it on again with power button.
It monitors battery voltage and switches off when getting low so keeping sufficient to start.
I've just bought an Android Unit and playing around with it digging in controlling the unit by can bus.
The Android unit only switches on with KL15 ("Ignition/Acc") CanBus Message or Acc Wire on and only switches off with that signal or wire off.
Unit Power Button only switches off screen drawing nearly full amount current and don't switches it on without previous mentioned.
The KL15 Bits are in CanId 000 Byte 0, you can send 000#FF twice for on ore 000#00 for off (found in some W2xx spec), Acc-Wire for no can is red at this unit.
It switches off with Ignition switch all off position, but you can switch it on again with power button.
It monitors battery voltage and switches off when getting low so keeping sufficient to start.
I've just bought an Android Unit and playing around with it digging in controlling the unit by can bus.
The Android unit only switches on with KL15 ("Ignition/Acc") CanBus Message or Acc Wire on and only switches off with that signal or wire off.
Unit Power Button only switches off screen drawing nearly full amount current and don't switches it on without previous mentioned.
The KL15 Bits are in CanId 000 Byte 0, you can send 000#FF twice for on ore 000#00 for off (found in some W2xx spec), Acc-Wire for no can is red at this unit.
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
