Hi Everyone,

Am new at this, apologies if I break any protocols!

I need your help;

I have a mechanical issue with my Audi A3 2009 hatchback. Issue manifested itself by having light failure warning on the car and hazard lights turning themselves on when the engine is switched off.

I took it to the garage who 'cold rebooted' the vehicle by removing one of the battery terminal. This caused BCM Onboard supply unit, Part No: 8P0907063D to blow on one of the input sockets.

I am currently seeking a replacement but my question is; what would have caused the motherboard to blow? I am afraid of replacing it and the same scenario happening.

Any advice will be highly appreciated.

Regards,

Martin

Hi Martin....welcome to the Forum

My first thoughts are....which terminal did your mechanic remove first, only if it was the positive terminal then this can create a spike through the electronics. You should only remove the negative terminal first to isolate the electrical supply and not introduce any power surges through the system.

Additionally, if the electrics were troublesome before disconnection of the battery, then this could likely be an earthing problem which would account for the spike also.

Check the battery connections and earth leads first to see if there is any corrosion or poor connections before fitting any new electronic units.

Let us know what you find

Cheers,  Trevor

Hi Martin 

Welcome to the forum! :D

Oh dear sounds like an annoying issue, hope you get it fixed soon, sorry I can't really help with this, don't want to give you false info :)

Kind regards

Bradley

Thank you Trevor and Brad. Your comments alone are enough to lift my spirits... been bashing my head against the wall the better part of the day.

Trevor, would you mind pointing out the locations where I can find the earthing points on my A3 8P 2009 model?

The battery connections are bone dry.

I suspect the mech removed the positive terminal effectively roasting the BCM unit when reconnecting it. The affected terminal is circled on the attached picture. Are you able to highlight what electronic functionalities are handled by the terminal? 

 

 

Sorry Martin.....not sure of the locations for earth points but it's worth checking what comes out the battery and follow them down through the engine bay.

Not sure about the pin designation either but it would be handy to know what connects up to it