Intermittent Starting Problem

[Captainmagenta]

Hi team hoping you can help with a problem on my A3 convertible.  Sometimes when I turn the key to start the car nothing happens. The dashboard lights come on as expected but there is no sound from the starter. I can turn off and on again - still nothing or might start. Third time it starts as normal .  Then days go by with no starting problems at all.    
Battery was new last year and checks out as fine.   Any ideas what might be going on?

thanks

[Steve Q]

I'd recommend a diagnostic check to see if any fault codes flag up. Could be a crank sensor. 

Is there any red light on the dash which could indicate an issue with the imobiliser? 

[Captainmagenta]

Thanks Steve. I should have said no fault codes show up on OBD. 
I wondered about the immobiliser but no red light on the dash.

[Steve Q]

Odd there's no fault codes. When was the car last serviced. Could it be an issue with the HT leads or spark plugs for example 

[Captainmagenta]

It’s serviced by Audi in July every year. It’s the intermittent nature that’s odd. I did a 400 mile round trip recently with lots of stopping and starting and this happened only once. 

[Magnet]

Hello Alan,

Check connection on to starter motor solenoid.

[Captainmagenta]

Thanks. I think when the weather warms up a bit I need to get my head under the bonnet and do as you say.

[Captainmagenta]

Just an update. I still can’t find what the issue is and the car has recently behaved itself so I will get it looked at next service,

[Kev-P]

I know its not the same car, but I had a similar issue on my XKR. It turned out to be a bit of corrosion on the ground cable from the battery to the car body. I just removed the cable, cleaned with wire brush & reconnected and not had a problem since. May be worth a look.

[Magnet]

Thanks Kev. but beware of disconnecting Audi batteries, and the potential need to re- code after. 
Over on the Jaguar forum, there seems to be opinion that JLR systems don’t need recoding after fitting a replacement battery, but….

[Kev-P]

6 minutes ago, Magnet said:

Thanks Kev. but beware of disconnecting Audi batteries, and the potential need to re- code after. 
Over on the Jaguar forum, there seems to be opinion that JLR systems don’t need recoding after fitting a replacement battery, but….

Your right, they certainly don't on the older jags. Would it be possible to connect a battery charger to an alternative ground point to try and kid the car that the battery is still connected.

[Captainmagenta]

I haven’t removed the ground point but have looked at it and it seems pretty sound - but it’s worth another look noting the coding issue. Thanks guys.