New to Bongos - just got one sent over from Japan. Have changed the speedo dial face and reassembled the unit without the perspex facia (for calibration purposes) but now the fuel gauge isn't working.

Even before I took the unit out it was painfully slow taking ages for the needle to move from rest position but now it just doesn't seem to want to move at all.
Is slow normal?
I checked all the contacts are clean and secure on the printed circuit at the rear of the unit and the connectors are in securely but to no avail. Any help or advice would be appreciated but please bear in mind that I am not at all mechanically or electrically minded.
Many thanks
Bongowner