Hi I have a 3 yr old Superb 1.9tdi Elegance spec, which has recently started to drain the battery a bit more than usual (I have had a couple of mornings where it is sick enough that it turns over, but the relays clatter away and it is clearly not going anywhere). After a charge, it's ok again for another week or so. Halfords reckon the battery is 75% good, but I have a new one on order (higher power Varta as recommended in another thread).

Today I noticed a high-ish pitched whine coming from the rear near side, sounding a bit like a dodgy switched-mode power supply. This seems to be related to side-lights, as it goes on and off with them, and is the same whether the engine is running or not. Presumably the lights are driven via the can bus - so it could be something related to that.

I wonder if the two issues are related ? Any ideas ? And any ideas where the noisy bit of kit might be hidden - I am assuming its somewhere near the rear light cluster, but don't really want to go taking the interior apart to track it down.

Hi I have a 3 yr old Superb 1.9tdi Elegance spec, which has recently started to drain the battery a bit more than usual (I have had a couple of mornings where it is sick enough that it turns over, but the relays clatter away and it is clearly not going anywhere). After a charge, it's ok again for another week or so. Halfords reckon the battery is 75% good, but I have a new one on order (higher power Varta as recommended in another thread).

Today I noticed a high-ish pitched whine coming from the rear near side, sounding a bit like a dodgy switched-mode power supply. This seems to be related to side-lights, as it goes on and off with them, and is the same whether the engine is running or not. Presumably the lights are driven via the can bus - so it could be something related to that.

I wonder if the two issues are related ? Any ideas ? And any ideas where the noisy bit of kit might be hidden - I am assuming its somewhere near the rear light cluster, but don't really want to go taking the interior apart to track it down.

First two thoughts that cross my mind.

1. Do you have electric parking brake? ( models further down the range don't, but wonder if Elegance does?) Problem could be related to the motor not cutting out when brake is applied.

2. Problem with the twin-door locking mechanism. Motor that switches hinge lock not cutting out?

Long shot - you don't have an inverter and 240 Volt outlet installed in the boot? - same whine as a switch-mode psu.

Thanks ksr, but no, it's a manual brake, and definitely not the twin-door mechanism (I know that sound well!), and there's nothing else plugged in to the boot power socket.

I can turn the whine on and off simply by switching the lights on / off - 100% repeatable.

The only other installed item which I didn't mention is that I do have a towbar fitted, and so presumably there's a box of tricks in the back somewhere to feed the electrics socket - I've not tried plugging a trailer in to see if that makes a difference.

I guess I'm going to have to strip the interior to find out what's behind there...

The only other installed item which I didn't mention is that I do have a towbar fitted, and so presumably there's a box of tricks in the back somewhere to feed the electrics socket - I've not tried plugging a trailer in to see if that makes a difference.

You may well have found the source of both the noise and the current drain........

Well that is at least a 50% success - pulled the fuse for the towbar wiring, and the whining stopped. Put it back and it didn't restart - will check whether the trailer lights work at the weekend, and will also monitor whether it makes any difference to battery life.