I agree this thread is a waste of time.

 

It does not work that way. Your battery is not filtering properly, the BCM is getting all confused because of this.

Your battery is getting weak, well, "weak", but that does not mean it can't start the car, what it means is that it's internal capacitance is diminished, at least in aspect(s) such that it cannot filter the noise/ripples from the alternator, the spike from the engaging and disengaging of the starter, etc. This means the BCM is living with this noise and it can't keep track of what it's doing because of it.

Another theory is that the voltage it provided sags too much during starting, causing the BCM (and other modules) to loose their minds.

We've all seen it, countless times. Keep screwing around like this and you are gonna likely end up with a bad airbag module. Go ahead, ask me why I say this. Then ask me what THAT costs.

Now, you asked for advice and won't listen.
So......
Let's make the thread useful - everyone, post pictures of your favorite hot celebrity. I'll go first, America's favorite Canadian singer and all-around hottie:

 

? I guess This Canadian has spent too much time in the basement. Who is she?

 

AVRIL LAVIGNE!

DAMN, Dave -I think you pissed her off....

 

ROTFLMAO... wasn't expecting that..

 

Didn't surprise me -
These millennial celebrities can be as sensitive and self-centered as a young bride on her wedding day.

 

James1549 et al, in no way have I dismissed your learned advice. On the contrary, I have focussed purely on the battery being the issue. I have been slow to proceed as you all suggest only because I've been trying to get more info. I'm not a motor engineer but my adult working life has been all about problem analysis and solutions. All my previous cars have been obvious when the battery has started to go, it struggles to turn the engine over and then fails. What is new to me and something I hadn't taken from your posts was the "early" in early warning system. I'm now assuming this means that the battery is still ok but not for much longer. Anyhow, thank you all, new battery is ordered. I'll make one final post (hopefully) on this matter in the new year to confirm the problem has gone.

 

Thank you , it's always good to close a thread, with the answer that sloves the problem, that started the hunt for a solution.

 

Hi Everyone, I was looking for some help......again, my spoiler has decided to deploy itself at slow speeds, IE while crawling in traffic, parking , reverse or forward, no idea why, it`s a 2005 Roadster UK model as I live in the UK, I then to need to switch off engine, remove key, insert key put the spolier down,and start it up again and set off again, all is then fine until the slow moving manouvres , it goes up and down at the correct speeds normally, but not if I`ve had the deploying issue at slow speeds then it will just stay up constantly until I reset it, any guidance would be brilliant, Regards, Teak

 

First, I would get one of those cheap cigarette lighter voltage displays from eBay.
https://www.ebay.com/itm/Digital-LED...9XVg24&vxp=mtr
or, if you want it fast, Amazon :

Seems when you are at low RPM your voltage is dropping.
This would indicate an alternator issue.

 

without any further information I would have to completely agree.👍

 

I was helping another owner with a weird spoiler happening..lol. When it deploys, pull to a stop , then retract it with the switch. Keep the switch down until you hear a beeeep! If you don't fully go thru the cycle, it does what it wants..
Let us know.

 

Hi Steve Jr, I'd already tried that and it doesn't work I'm afraid, I need to stop, switch off the engine, start it up and then put it down again, I'll try the cigarette lighter charge display and check the charge rate at tick over, thanks anyway, teak

 

FYI - update on original post re aerofoil engaging.
New battery (74Ah, 680CCA) installed over a week ago and no further issue.
Thank you all for your help.

 

Problem analysis and solutions? I guess you a analyized this one from top to bottom, side to side and inside out.

 

Another satisfied customer thanks to the Forum. 🤙

 

Thanks for posting solution.

 

😗 Oh I didn't come up with the solution I'm just a spectator.

 

Hi everyone, I fitted a brand new battery about 3 weeks ago and it has made no difference whatsoever I'm afraid, I've ordered the cigarette lighter device and I'm waiting in it arriving, it also deploys when reversing, strange but true, thanks for all the help, regards, teak