Should the engine control relay hum when the motor is running? The black plastic housing for the ECU and the ECR has a hum coming from it. I see rock Auto sells this relay for just $127. Anyone know if that is an OEK MB part? Doesn't seem like somebody would make them besides MB but what do I know! Thanks. I know the PUMP is good and the SC clutch activates when hot wired, something in between. Mark