Buzzing / Humming noise

Hi all…. got a 1989 mk1 cab 1.8 gti 8v
When ignition on & then engine running there is a buzzing / humming noise from under the rear seat area. This fluctuates in level when indicating or lights turned on or off so definately electrical.
A local independant VW chap suggested the inner fuel pump under the seat had packed up. Changed that & guess what….? still bloody buzzing.!
Really want to cross this off the list of things to sort so any suggestions ideas would be helpfull.
Cheers
Lee

TBH i'd have thought it would be the main pump just in front of the OSR wheel.  Notoriously noisy.  Fire it up and have a listen in that area.

HTH

Thx mate. I've had my head everywhere if you pardon the pun..! Its a noise that just seems around the wole OSR area…!
Its damn annoying…!
Might get it up on the ramps again this saturday. Really want to get it sorted.
Ta
Lee

It does sound like the fuel pump, but mine is new and it still whines away. Which is understandable when it pumps 90% of the fuel out and then back into the tank!!!

If Everything is working ok don't try and fix it, its normal, mine also changes tone on lights and wipers,  would attribute that to load on the engine and more fuel being required.

Rob