A real puzzle - Electromechanical fault

[Mark McLeod]

The two PDP protected 12v & 24v outputs are good down to about 4.5v, maintaining their 12v/24v.
The 5v PDP output get cut off at around 5.5v.
Beware sharp sudden spiky dips at low voltages.

See Power Distribution Board.pdf, pages 6 & 7 Specifications for minimum voltages for the 24v protected supply, 12v protected supply and 5v outputs.

P.S.
Correction: the regular 12v outputs do not get cut off at low voltage. They follow the battery on down.
But, something cuts controlling PWM/relay outputs at less than 6v, so the effect is the same.