Burnt Out

I was called in to look at a Ginneta G50 race car that was burning out relays.

Used in the British GT Championship it would start and run fine but would burn out its relay before the end of the race resulting in a DNF.

A new pump and a few different relays had been tried, but the fault remained.

I used a amps clamp to test current draw, on the control and output sides of the relay.

I discovered that the control side of the relay had abnormal current draw, but where was the resistance, classic cause and effect diagnosis.

The effect = burnt out relay.

The cause = excessive resistance in the circuit.

A quick check with the scope(image shown above) showed higher than acceptable volt drop on the earth circuit.

This after prolonged used caused the relay failure, replacing a section of loom had this GT4 back on the grid.