We had booked in this week an Audi A1 1.6 CRD with a malfunctioning dash display . The described fault was a faulty fuel gauge along with a message indicating the fuel gauge fault and also the outside air temperature display was misreading . The fault was repeatable and a complete global scan of the vehicle revealed dash and engine faults for the fuel gauge and the outside air temperature . It was noted that the in-tank supply pump was very noisy . The interesting thing we found was that the fault would clear and the dash display worked fine until the ignition was cycled and the in-tank pump was primed .We decided to investigate the noisy in tank pump and found that the fuel filter was partially blocked overloading the pump. Referring to the manufacturers wiring diagram we tested the wiring at the fuel pump and quickly found that the earth for the fuel gauge would go to twelve volts when the pump was activated . Removing the in-tank pump and the internal connector revealed the problem the pump supply terminal had over heated and melted the plastic connector causing it to short to the earth terminal and as a result the earth for fuel gauge and outside air temperature where being shorted out together .
Unfortunately the dash circuit board had been damaged so with a new in-tank pump installed the fuel gauge and outside air temp faults were still present so we installed an extra external earth which solved the problem.
The conclusion was that lack of servicing \ long life servicing had caused the fuel filter to become restricted and as a result over loaded the in-tank electric pump pulling so much current that it melted the terminal block proving once again that regular correct servicing pays dividends in the long run.
