Hookie
New Member
Please can someone tell where the auxiliary (small) battery is located in this car? I've googled and YouTubed it and am getting nowhere. Any help much appreciated! TIA
2010 C220 Cdi W204 Estate
- Thread starter Hookie
- Start date
Chrishazle
MB Enthusiast
- Joined
- Nov 13, 2008
- Messages
- 5,608
- Location
- Nr Ashford, Kent
- Car
- 2008 S204 C220CDI Elegance Estate Auto, 2008 R171 facelift SLK280 Auto.
I have a 2008 S204 C220 estate, it only has 1 battery, the big one under the boot floor on the offside.
OP
OP
Hookie
New Member
One battery or two, and therein lies the mystery. Last week I had an issue when the car refused to start until I jumped it. The battery is almost new and is in excellent condition. I got the car home, decided to charge the battery just be on the safe side. Opened the bonnet. Locked the car. Removed the battery leads and the alarm went off. Flashing lights and horn blaring! Hence my thought it must have a second battery? The next day when the battery was fully charged, I plugged in my OBD2 reader which came up with about 20 error codes all relating to low voltages, which I feel points to the second battery? Just wish I could find and check it over.
- Joined
- Nov 1, 2008
- Messages
- 19,324
- Location
- Bournemouth/Poole Dorset
- Car
- W210 E280 x2, w211 E55, W212 E63 biturbo, S204 C180K
Does your car have stop/start?
If not, you only have the one battery in your S204.
Your reader was probably showing historic codes when the battery was flat.
Clear the codes and start the engine. Should have no codes showing then.
If not, you only have the one battery in your S204.
Your reader was probably showing historic codes when the battery was flat.
Clear the codes and start the engine. Should have no codes showing then.
SpikyMikey
MB Enthusiast
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- Nov 4, 2020
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- 6,978
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- The Sunny South Coast
- Car
- BMW F31 330i LCI M Sport Shadow Edition Black Series AMG Touring
Not sure about Mercs, but some car alarms have their own back up batteries
W204 Alarm Going Off | Electronics and Audio
Hi, I have recently purchased a 2012 C180 Estate to replace my wife's car but having an issue with the alarm. It has been going off sporadically, I checked the battery voltage (which was just under 12v) and replaced the battery. The alarm hadn't gone off since then (10th November) until two days...
forums.mbclub.co.uk
It would appear that the siren has its own battery (I think most, if not all, do).
OP
OP
Hookie
New Member
Thanks to everyone for your replies. Maybe if I explain in more detail what happened, someone may be able to come up with an explanation and solution? I had visited a friend, parked the car, engine off and ignition key left in situ. However, I left the side lights switched on. Normally I take the ignition key out and warning peeps tell me the side lights are on, and I then switch them off. So, side lights were left on for about 15 minutes only, until I switched them off. Went back to the car about half an hour later and it would not start, followed by messages on the dash about various things not working. Jump started the car, got it home and connected a battery charger and left it charging all night. The battery is a Yuasa, about 18 months old and checks out at around 95% of it's quoted CCA. Yet the OBD2 check said that the problems starting the car the previous day was due to low battery voltage, under 9V. So, is leaving the side lights on for 15 minutes going to drain the battery to such a degree that it won't then start the car? This sounds very improbable to me. Hence my thoughts about it being due to the car having a second small capacity auxiliary battery, which as yet, I cannot find. In normal day to day use the car runs fine and is never a problem to start. This whole scenario has happened once before when I left the car parked with a 12v cool box plugged into the 12V auxiliary socked in the back, with the ignition car in the necessary position to keep the 12v socket running. Here again the car would not start and needed jump starting after having left it for about half an hour. I've been careful ever since not to leave things powered in the car. I've used the cool box in other cars and never had this problem, and it points to some quirk or issue with the Mercedes. Any thoughts please, and I say again the main, big battery is perfectly good.
