Does anyone out there know what the spec is of the back-light bulbs in the factory fitted reversing sensor control unit? (the one fitted onto the top of the dash)

I must have blown mine when I re-connected the batteries after Bongo had been sitting on my drive for 4 months



They are 3mm dia wire tail bulbs and I assume that they must be at least 14volts as they see the full battery charging voltage but I have found some on the WWW up to 28volts.
So before I go off and buy a selection to try thought i might as well ask the experts first.

Anyone got the schematics for it?
Regards Grahame