Oil Warning and Temperature Warning Lights

[kjm511]

Hi,

My son owns a 1993, 1043cc Polo. Today, the oil and temerature warning lights are remaining on but thye buzzer does not activate. The engine is not running hot and seems to be running fine. I have tested the electric fan and it works okay. I have checked and cleaned the various earth points around the engine compartment. The workshop manual suggests the usual things but these all seem okay. I am wondering whether this could be an earth fault, as the sensors appear to link back to some sort of control module which I assume is located behind the speedo head but U cannot find where this module earths. I am presuming that if that module has failed, the buzzer would sound also?
I would welcome any suggestions as to the likely cause and how to remedy?
Thanks