My oil level light does not come on when I turn on ignition. Light works because when I short oil level switch wire to ground light comes on. But no longer comes on when ignition is first turned on. Have changed diode block and no difference. 2 wires on diode block have positive 12 volt, third goes to switch. So I believe problem could be in start relays but cannot find any info on what these do with concern to oil light. Even if anyone knows internal circuitry of these relays would help. THANKS