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[LostKiwi]

The resting voltage is 12.2 volts

That's much too low.
Ideally it should be 12.6v or above, minimum 12.4v. That low suggests the battery is shot. Take it somewhere to have it tested to confirm.

 

[Tony Dyson]

The resting voltage is 12.2 volts

That doesn't surprise me if my suspicions are correct in post #17 the battery has never received an adequate charge voltage from the car! Did you enquire about the original specification battery?

 

[robmc52]

That doesn't surprise me if my suspicions are correct in post #17 the battery has never received an adequate charge voltage from the car! Did you enquire about the original specification battery?

No I haven't had time today to find out about this, do you mean that the alternator isn't charging at the correct rate, or the battery should be capable of taking a 14.8 volt charge? Looking at the specs for various batteries, I can't see a reference to to this aspect, they just mention the cranking amperage and the amp hour rating, unless I'm being thick and am missing something.

 

[Tony Dyson]

No I haven't had time today to find out about this, do you mean that the alternator isn't charging at the correct rate, or the battery should be capable of taking a 14.8 volt charge? Looking at the specs for various batteries, I can't see a reference to to this aspect, they just mention the cranking amperage and the amp hour rating, unless I'm being thick and am missing something.

Your car will be programmed with a charging profile to charge and maintain the specific technology battery factory fitted to your car, this information isn’t freely available from MB but the charging parameters of the battery will be available from the manufacturers in their technical documentation and not usually printed on the battery itself. In my experience the typical optimum charge rates for the type of battery currently fitted to your car are in excess of the 14.2v you have measured as a charging voltage for any of the charging functions which is the reason I suspected originally that the current battery fitted is not the same type as the original factory fitted option, the sooner you can confirm this, the better you can be advised by the forum members.

With a current resting voltage of 12.2v your battery is performing at a reduced capacity of around 50% and as LK already advised, needs repair/replacement, my advice would be to confirm the correct model it should be replaced with. If the current model is the correct one, then it has simply reached the end of it’s useful live and should be replaced and under warranty if under 5 Yrs old.

 

[robmc52]

Well I've fitted a new battery this morning, from my local dealer. Part number A001 982 82 08/26. Standing voltage is 12.6 volts (there's a note on the top that says 'charged 7/7, doesn't say what year!) Charging voltage is still 14.2 volts, there wasn't anyone in the parts department who could give me any information about the charging profile, so I'll ask my indy for his advice.
Still getting errors coming up, pre safe this time, then the gearbox is hanging between shifts. Turn off, turn on and it's back to normal.
I did 250 miles on Saturday with the aircon and radio etc turned off, just to see if a lighter load would make any difference, no errors during the journey. I wonder if this points towards a low charging rate, as Tony mentions above.

 

[Tony Dyson]

As long as your new AGM Battery maintains a resting voltage of 12.6v then your car's charger is doing it's job, typically an AGM battery will accept a maintenance (Top-up) charge from as low as 13.6-8v unlike your old Gel battery, that simply needed higher charging voltages, sorry I don't have any further suggestions for your other intermittent faults but I'm sure someone will be along soon with further inputs.

 

[robmc52]

Thanks for your advice so far, Tony. The car is going in to my indy today, as despite the new battery, the resting voltage has gradually dropped each time I've checked. It's now down to 12.2 volts from about 12.6/7 when installed yesterday. The pre safe warning now comes up as soon as the engine is running, and doesn't reset if I turn it off and leave it for a while. One for Star I think!

 

[Tony Dyson]

Thanks for your advice so far, Tony. The car is going in to my indy today, as despite the new battery, the resting voltage has gradually dropped each time I've checked. It's now down to 12.2 volts from about 12.6/7 when installed yesterday. The pre safe warning now comes up as soon as the engine is running, and doesn't reset if I turn it off and leave it for a while. One for Star I think!

Well that's not-so-good news but I'm sure your Indy will get to the bottom of it and hopefully soon!

 

[joderest]

sounds like a parasitic draw somewhere, some thing is drawing power whilst vehicle turned off

 

[mattkh]

My penny is on a vacuum hose leak.

 

[robmc52]

Just an update on this. Picked the car up this morning from my indy. they're given it a couple of 'long, hard runs' on our local test track, with Star on board, then left it idling for an hour in the hope that it would cutout, it's been running absolutely fine...
I then took it for a 50 mile run, the charging voltage showed a steady 14.2 volts, my man says that's as it should be, if it needed to be higher then it would have shown up on Star.
I do wonder if the old battery was knackered, and the new one just needed a bit of a charge. I checked the standing charge when I picked it up, 12.5 volts, that's after sitting all night at the garage, so will check it in the morning and see if it's dropped.

 

[robmc52]

Well I think I've finally got to the end of the problems with the car. Basically 2 separate faults at the same time, firstly the low battery giving spurious errors with all the different messages that were coming up, and secondly a speed sensor fault that was triggering the pre safe warning.
This came to a head yesterday when the car went back on Star, which showed a fault on the conductor plate, the man said he had no idea why it should cause the pre safe warning, but that's what it showed on the diagnosis.
I then left the garage, after arranging to take the car back in next week, as they are very busy this week, and got 10 miles up the road before the gearbox became permanently stuck in 1st gear.
Once the breakdown guy arrived, he cleared the error code, and then followed me back to the garage, in case it went again but it held up ok.
The man said he'd replace the conductor plate when he could fit it in, so I got a call this morning telling me he'd changed it! He ordered the parts yesterday afternoon, let the oil drain out overnight, and changed it all before having his second coffee this morning, top bloke!

 

[Tony Dyson]

Glad you got it finally resolved and put the thread to bed!