Hi all,

had a catastophic electrical failure with the C class W204 2012 year of manufacture.
Turned the ignition on and came up with loads of faults.

1st stage ignition I had the following

• The media console wouldn’t turn on
• the air conditioning would turn on
• the driver restraints where alarming faulty
• the interior lights didn’t work

2nd stage ignition I then had

• esp failure
• dsp failure
• cruise control failure
• speed assist failure (console workshop)

engine would start without to much issue

• automatic gearbox was locked in park
• radiator fan ramped up to full speed instantly
• power steering was almost non exsistant

after ringing around and a lot of digging most people recommend inspection of the “F32” Fuse box, this is the box located next to the battery with the main positive terminal for battery jump leads.

I disconnected the main main negative terminal of the battery from the car, then removed the 3 primary cables on the the top of the F32 fuse box, tested every fuse in both the engine bay fuse box and the boot fuse box (all where good) pulled every relay in both boxes and ensured they where reseated correctly and securely.
I reconnected the cables for the F32 fuse box and then the main battery negative cable, the battery was isolated for around 30 minutes which must have initiated a hard reset of the electronics.

I then jumped in the car and turned the ignition to find all the faults had cleared !!!!!
I tried starting the car but sounded like the battery was low on power.
I measured theVoltage which was down at 11.96Volts (engine off) so connected up jump leads to a healthy battery.
started the car first time and left it running for 30 minutes to get some life back in to the battery, monitored the battery Voltage for a while and the alternator was charging fine at around 14.3volts the battery now sits healthy at 12.8volts when the engines been off for a while and 6 days later I’ve had not a single alarm or issue.

Many threads I’ve seen say this is a fault of the SAM controller and some people have even suggested ECU.

I have no no idea what intiitared the battery in to draining, but there was no mention of low voltage in alarms and the battery seems to hold charge fine since.

So if you are having this issue, try a hard reset and check your batteries voltage before getting in to expensive garage repair and investigation costs.

Saved myself £100 for towing to the garage and £80 an hour for investigation.