Hi, is a turbo cab? if so the electric roof will have probably been bodged, straight to the battery you will basically need to check the wiring from the switch (near gearstick and make sure its earthed properly (prob under carpet/floorpan )
If if its a 3i cab then you are in a similar situation but will have to trace the wire thru the loom to make sure its connected up properly.
All this is of course assuming the pump actually works!
CheeRs
Phil