Discussion
My SL55 has been stood for a few weeks. Batteries were fairly flat in that I could not get in the car without the key yet it started fine. Presume the aux battery is running all the door systems etc. and main battery starts the engine.
Anyway the dashboard lit up with a nice red battery symbol and a visit workshop message.
So I disconnected both batteries and charged them separately. Reconnected everything and everything is working again. Car drives fine but..... the dashboard battery indicator/visit workshop is still on. Cleared the malfunction memory, but it comes back after a few seconds.
Now I know both batteries are fine - they were both replaced last year as was the voltage regulator on the alternator.
So....... does it maybe need a long run so it 'learns' everything is OK. I know it these cars are sensitive to voltages so maybe it's not quite fully charged or something.
Any ideas?
Anyway the dashboard lit up with a nice red battery symbol and a visit workshop message.
So I disconnected both batteries and charged them separately. Reconnected everything and everything is working again. Car drives fine but..... the dashboard battery indicator/visit workshop is still on. Cleared the malfunction memory, but it comes back after a few seconds.
Now I know both batteries are fine - they were both replaced last year as was the voltage regulator on the alternator.
So....... does it maybe need a long run so it 'learns' everything is OK. I know it these cars are sensitive to voltages so maybe it's not quite fully charged or something.
Any ideas?
My 350 would throw up all sort of warning messages if it was left standing for a few days with the "convenience functions temporarily unavailable" displayed.
The common fault showing was light sensor, visit workshop, and brake service. visit workshop which immediately makes you think SBC pump. They would usually disappear after a 20 min run to put charge back into the aux battery, but some would stay for a few hours, or maybe coinciding with using the car again later.
I did change the starter battery at first not knowing it was the aux battery causing the issue and I did need to get the car plugged in to star get rid of one message after disconnecting the battery. I think it related to a sensor but can't remember exactly what the fault was now. It took a few minutes to clear on diagnostics and all was well with the world again.
The answer has been a trickle charger connected to the auxiliary battery over the last few months. Since then I have had no issues whatsoever, finger crossed.
No leaks on the roof seals yet either
Just re read your post and it was the same battery message/warning you have I had to plug in to star to erase
Alex Crow did this for me and said it related to a sensor after disconnecting the battery.
The common fault showing was light sensor, visit workshop, and brake service. visit workshop which immediately makes you think SBC pump. They would usually disappear after a 20 min run to put charge back into the aux battery, but some would stay for a few hours, or maybe coinciding with using the car again later.
I did change the starter battery at first not knowing it was the aux battery causing the issue and I did need to get the car plugged in to star get rid of one message after disconnecting the battery. I think it related to a sensor but can't remember exactly what the fault was now. It took a few minutes to clear on diagnostics and all was well with the world again.
The answer has been a trickle charger connected to the auxiliary battery over the last few months. Since then I have had no issues whatsoever, finger crossed.
No leaks on the roof seals yet either
Just re read your post and it was the same battery message/warning you have I had to plug in to star to erase
Alex Crow did this for me and said it related to a sensor after disconnecting the battery.Edited by Monkeylegend on Tuesday 30th May 09:16
One thing to consider with lead acid batteries is they degrade very quickly if you leave them flat.
Once the terminal voltage is below around 11v the cells start to sulfate which reduces the capacity. A sulphated battery will appear to charge normally and as it now has a reduced capacity it will charge very quickly but obviously go flat rather quicker than before.
Just because the batteries were new last year doesn't mean they are in good condition if they have been left discharged.
On my 350 I had to clear the battery error via the OBD port, the system is not clever enough to figure out you have fitted a nice new battery.
Once the terminal voltage is below around 11v the cells start to sulfate which reduces the capacity. A sulphated battery will appear to charge normally and as it now has a reduced capacity it will charge very quickly but obviously go flat rather quicker than before.
Just because the batteries were new last year doesn't mean they are in good condition if they have been left discharged.
On my 350 I had to clear the battery error via the OBD port, the system is not clever enough to figure out you have fitted a nice new battery.
Sorry, should have updated this. Decided to take it a Merc specialist that is some distance away, got there and no more red battery message. They checked everything bit all is well. Their theory is the batteries needed further charging off the alternator to get the system to 'settle' at the right voltage and no longer detect an issue. Anyway all is fine now.
PS you're right about the SBC, when the alternator regulator failed last year that exact issue became very apparent ... trying to stop 2 tonnes of car with no SBC is not fun.
PS you're right about the SBC, when the alternator regulator failed last year that exact issue became very apparent ... trying to stop 2 tonnes of car with no SBC is not fun.
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