740 & 760 91 740 Heater control issues - Fan always running with acc power on

Hey Crew,

Just got pops 740 wagon project moving under it's own steam and at some point the heater controls have seemingly given up on us. It's a bit of an odd fault but here's what i've found:

Key to acc and onwards the fan will come on and seemingly full speed... switch does nothing at all doesn't turn it off or change the speed, direction door doesn't change and neither does the temp. The fresh/recirc air switch is illuminated but turning it on or off doesn't change the illumination.

Strangest thing in troubleshooting today which is leading me to believe that the control/switch unit itself is faulty is that with the unit hanging loose if you earth the chassis of the unit it will spark and the fan will drop out until you remove the earth contact.. yet it doesn't blow the fuse.

I've checked and short of comparing with diagrams the wiring seems OK to back of the unit and fan etc. and earth points are strong (that i can find)

Appreciate any assistance or if anyone has a unit the same as pic please let me know (located Tas but happy to cover postage on top) Cheers!


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