It depends which input on the Motec you have it wired up to. It's one of the Sw ones, mine is on Sw In 3. You set that to air conditioner request. Logic polarity on mine is set to 1, and the AT low and high levels are set to 5v and 6v respectively.
As well as the input you need to set one of the outputs to the aircon clutch. Again it depends which output you've got it wired to - mine is on Aux out 2 - you set that to A/C clutch. The parameters for the A/C clutch I have set to:
On throttle pos 90
Off throttle pos 95
On RPM 5500
Off RPM 5800
Recover time 2
Polarity 0
Output mode 0
I can't say for sure those settings are right because my aircon has had a leak since before the Motec went in so it's never actually been tested, but that's what Owen's set up.