lordelpus

Hi,

First post. OK I need some advice. I bought an R Class 320Cdi , 15 years old(yes stupid but love the car). Two months after purchase the battery went flat and just before this the car alarm would go off whilst driving and intermittently when parked the alarm would go off with no siren sounding. A new battery was installed. Seemed fine..Then a few weeks ago the car got stuck with the message drive to workshop withought changing gear Had a look online and thought it maybe the ISM. Left it overnight and it started the next day. All OK. Then the same happened. Went to the local specialist who said ,yes it is the ISM,replced it, and they also disconnected the siren .
Yesterday, went to the shops. 20 minute shop and come back and the battery was flat. Was in a low signal area so could not get to recovery so called my brother and we jump started the car. This morning she cranks up first time. Call recovery and off course as the car is working they will not recover to the garage. They checked the voltage, 14V..OBD check came up with many messages stating intermittent voltage drop to 7V causing numerous errors.
Have to take the car back to the sspecialist and the guy seems to know his stuff., but get the usual needle in the haystack conversation.
Anyone have any similar experiences or clues to help ??
Regards.

Tsumi

Have you replaced the secondary battery? That could have been the root of the ISM failures and now causing a drain on your primary battery.

lordelpus

HI,i do not have a secondary bettery as 2007 model ?? Is that right ? Many thanks

Tsumi

There is a second battery used to power the transmission in case the main battery dies.

https://www.benzworld.org/threads/ho...-w164.3048907/

lordelpus

Hi, Thanks..will look at that..very useful..I thought the seecond battery only came in 2008..could well explain it. Regards