Key no longer opens roof remotely

[fatbaldboy]

Hello there,

Roof still opens/shuts using the buttons in the car but no longer opens with long press of unlock. Tried with both fobs, no joy.

Any idea?

 

[Marcoose]

Every time electric and electronic gremlins pop up, I immediately think battery. How old is yours ?

 

[fatbaldboy]

Hmm, not sure. Good shout though.

I've a battery maintainer / charger - I'll hook that up and try the fob: if it works that'd be support for the battery theory wouldn't it

 

[matsmith749]

Not really.

If the battery is over 10 years old, no charger or maintainer will help much.

A new battery has 100% (ish) capacity available to it at full charge - 14.x volts / delivery of over 100 amps. It loses some of that every time you start the car, and also gradually over time as the chemistry within the battery slowly degrades. If the battery has ever been allowed to fully deplete it is likely permanently degraded & will never retain it's full capacity again.

After say 5 years - even when fully charged & hooked up to a battery maintainer that says 100% - you only have maybe 70% of the strength of a new battery.

After 10 years its 50% or less (even though the charger still says you have 100% - it's not true). A 10 year old battery, fresh of the charger supposedly saying 100% will only maintain that level for literally a handful of seconds before it is right back to where you are now - fooked.

Physics cannot be beaten - these batteries deplete every year & the e89 is incredibly sensitive to it.

New one is 100 quid.

 

[fatbaldboy]

Thanks for the maths!

Is there a way you'd recommend testing before dropping the money for a new battery?

At the moment I obviously don't know it's the battery that's causing it and it's not a terrible inconvenience.

 

[matsmith749]

Open boot - look at battery - locate manufacture date.

If >5 years, it's likely a problem.

If >10 years, it's definitely a problem.

If you have access to a proper test equipment specifically for vehicle batteries, you might be able to evaluate it better.

I wouldn't use halfords et all for this test - and to be honest - the £100 for replacement is likely less than it costs to properly verify.

I cannot say for certain if poor battery performance is the root cause of this specific roof issue - but it's a likely culprit if the cell is degraded, as are 100 other apparently unrelated glitches around the e89 whenever voltage drops a tiny amount.

I've had en e89 for years & seen a lot of comments on here - bad battery is the root cause of a huge % of anything 'odd' electrically. Also the #1 cause of breakdowns according to the AA/RAC.

This car is a minefield of complex electronics (10+ CPUs) that like to throw a fit whenever the battery drops below whatever threshold they have set. It doesn;t warn you that the battery is at fault - it just does weird s**t.

 

[B21]

Batteries,,,either the fob batteries are dying …if it’s not comfort access then it’s a pain to replace the non replaceable rechargeable batteries…if it’s comfort access new CR2032s…

As discussed new main battery is the default first fix…

If you’re 35i only costs you a new main battery consider yourself lucky,,

 

[Zed Baron]

Your battery will have a date stamp on the top of one of the two terminals (week/year), if it's over 5 years old I'd change it. Try Tayna Batteries or the Battery Group for online prices (new battery will need registering to the car).