I have in my late 1990 van a unit called a PEM, very similar to a ZIG unit.
Wired up a cable from house to external plug in on van (all wiring as should be in relation to correct wiring.
When I plug it in the van and throw master breaker. The red light comes on

It also states that if plugging in an external generator the red light will flicker on & off, so dont worry, as generators have this effect...so more confusion...
So any ideas on which wires i should muck around with??