My van's heater (fan) controls have packed up, and seem to have some related wiring issues.

 

I've removed the old unit, found that replacement parts are £silly and am thinking about other options.

 

There are 4 controls - 3 mechanical (which I can sort), and some lights too (which I can sort), and one electric control for the fan itself.

 

The connector pin has 4 cables - red (Live?), brown (Neutral?), green (thingy that controls the fans speed?) and grey (no idea).

 

There is resistance through red / brown - have tried crossing red and green / red and grey but this doesn't make the fan kick in.  I've tested the relay via the battery and a multimeter, which seems to be operational, and I've also tried closing the circuit and replacing - none of which have turned the fan on.

 

What I would like is to have a switch that will just have the fan on full and off, but can't quite work out how.  Am happy running new wires from the battery but am now feeling a bit lost.

 

While I could just replace the lot, I would quite like to actually understand how it works.

 

Anyone got a clue?!

Sorry, they're only golden, not crystal.