Bunyip,
I've had exactly the same problem with my Tigerz winch in the past. It was corrosion in the contactor. The coil would pull the contactor together (the click) but corrosion, rust and lack of lube would inhibit the two plates from actually making on one side. It kind of got wedged at an angle...
I pulled it all apart, gave all the components a rub down with wet & dry 600 back to clean metal, rebuilt with half a tube of silicon grease and (touch wood) it's worked fine ever since. Ps, mine was less than a year old when this happened. The shop I bought it from didn't want to know as Tigerz had pissed him off by selling online direct. No reply from Tigerz... Been working ok for 2 years now.