On that Passat - there is a 1" wide drain hole at the very back of the engine bay, under where the battery is and A/C pipes route - it's prone to filling with crud and that causes water to run into the car through the pollen filter housing. IIRC the alarm / convenience module is in the passenger footwell, if it gets wet ( due to the above ) lots of things stop working

Worth having a look with a torch and a pipe cleaning brush to make sure its clear.

 

Our old vectra got blocked with leaves and did that.

Missus didnt notice, fan rusted up.

Annoying

 

I bought a 530d sport. I paid £10k as I wanted a fairly recently low mileage example but you can get them for about £5k

Great car for the money