[LOADED 70 JUDGE]

I am close to bringing my 72 TA back from the dead. I installed a new AAW dash harness , blower motor , and rebuilt ac controls. everything works including blower motor at all speeds. the mystery is the blower motor will not turn off . when you put the top slide bar in the off position the blower motor drops to low speed and continuously runs as long as the key is on . it doesn't matter what position the fan switch is on as long as the top slider is in the off position if you turn on the ac the fan works perfectly .The ac clutch engages and disengages as it should when the top slide is operated from off to on. Anyone ever experience this or have an idea? Thanks Ken