Servo noise

[colin.c43]

I have an annoying noise coming from the rear offside wing of the car.
It happens approximately every 15 secs. It's like a small servo/motor whining.
Any clues? What is it? Is it a problem?

(W202 C-Class C43)

 

[colin.c43]

Fuel pump?

 

[martyz]

more than likely.

 

[Justin1600]

Possibly the PSE pump, especially if you have a leak on your orthepedic seats. The pump will keep topping up the air level