2012 C207 E350.
For the last couple of months I've been having problems with brake hold not working. Especially on the way to work (~7am); but tending to be less problematic on the way home at noon. Hard to be conclusive, but cold/damp mornings are perhaps worse too. Sometimes, but not always, accompanied by a "something deactivated/inoperative" message on the dash (flashes up too briefly to read properly, but symbols were brake/abs related I think. No warning lights stay on).
Once, I got back in the car at supermarket and tried it in the parking space - working fine. (It hadn't been on the way there). Got as far as the lights at the car park exit, and it had gone again!
Dealer charged me for diagnostics a few weeks ago and found no faults so they did a "re SCN coding of the system". (Sounded a bit like "try switching it off and back on again" to me...)
It certainly seemed to improve it at first, but I've now had the problem a few more times again.
Also, it's ages since my Stop/Start has gone to active state. Even at the tail end of the summer it seemed to be going green less frequently than I was used to. Have only seen it green a few times since, even on journeys - and even then it didn't stay green for long.
(I know there's a lot of factors like temperatures, electrical loads etc, but I'm comparing with the previous few years' behaviour, with similar journey styles).
I've done a bit of googling and a recurring area to do with these systems seems to sometimes be the aux battery. I did find mine in the boot (the large-ish ~12Ah size) and with ignition off it measures 13V.
There seems to be a lot of variation in size & location of the aux battery, even on E Class models alone - is there a second aux somewhere or just this one?
Reluctant to pay for more 'head scratching' if there's something I can diagnose/fix myself.
Thoughts/info/suggestions welcome! Thanks.
For the last couple of months I've been having problems with brake hold not working. Especially on the way to work (~7am); but tending to be less problematic on the way home at noon. Hard to be conclusive, but cold/damp mornings are perhaps worse too. Sometimes, but not always, accompanied by a "something deactivated/inoperative" message on the dash (flashes up too briefly to read properly, but symbols were brake/abs related I think. No warning lights stay on).
Once, I got back in the car at supermarket and tried it in the parking space - working fine. (It hadn't been on the way there). Got as far as the lights at the car park exit, and it had gone again!
Dealer charged me for diagnostics a few weeks ago and found no faults so they did a "re SCN coding of the system". (Sounded a bit like "try switching it off and back on again" to me...)
It certainly seemed to improve it at first, but I've now had the problem a few more times again.
Also, it's ages since my Stop/Start has gone to active state. Even at the tail end of the summer it seemed to be going green less frequently than I was used to. Have only seen it green a few times since, even on journeys - and even then it didn't stay green for long.
(I know there's a lot of factors like temperatures, electrical loads etc, but I'm comparing with the previous few years' behaviour, with similar journey styles).
I've done a bit of googling and a recurring area to do with these systems seems to sometimes be the aux battery. I did find mine in the boot (the large-ish ~12Ah size) and with ignition off it measures 13V.
There seems to be a lot of variation in size & location of the aux battery, even on E Class models alone - is there a second aux somewhere or just this one?
Reluctant to pay for more 'head scratching' if there's something I can diagnose/fix myself.
Thoughts/info/suggestions welcome! Thanks.