Car wouldn’t start

[John Maddocks]

Hi went to start car this morning lights came on radio but wouldn’t start only changed battery last year under bonnet it’s a w212 220 could it be auxiliary battery went in phoned rac came back out to give last try and it started.

Many thanks John


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[robin.large]

The auxiliary battery is used to power all 'extra functions' when the main battery cranks the engine to start. If the aux battery is dead (a good indicator of this is when the car won't enter eco stop/start mode) then the main battery keeps powering these functions.
This does sound more likely your main battery is at fault. Or insufficiently charged (short journeys, cold starts, a/c lights etc all on can gradually bring down the charge.
Check any warranty that cane with battery?

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[John Maddocks]

The auxiliary battery is used to power all 'extra functions' when the main battery cranks the engine to start. If the aux battery is dead (a good indicator of this is when the car won't enter eco stop/start mode) then the main battery keeps powering these functions.
This does sound more likely your main battery is at fault. Or insufficiently charged (short journeys, cold starts, a/c lights etc all on can gradually bring down the charge.
Check any warranty that cane with battery?

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Thanks for your reply I have noticed the stop start has taken longer to go green it’s got a 2 year warranty I have battery cover with rac it’s just why would it start five minutes later? Thanks for the reply


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[robin.large]

If it started with a normal crank speed then something else may have been stopping it. Alarm/immobiliser possibly - has that played up at all?

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[John Maddocks]

If it started with a normal crank speed then something else may have been stopping it. Alarm/immobiliser possibly - has that played up at all?

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Thanks for replying yes I’m thinking something like that it’s never happened before and it did start as normal today


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