Hotpoint Aquarius CDT40 fault saying empty water?

My friend asked me to look at their condenser as it is showing that the water needs emptying even though it IS empty.
I've checked all the pipes and reservoirs, plus the pump for continuity.
The float switch is moving freely, as is the switch that it operates.

I metered the switch though and found there to be a slight continuity reading when the switch was open. Could this be sending enough of a signal to the board making it believe that the switch has been operated? Could it have blown a fuse on the board as a result? As it still shows the fault even when the switch is totally disconnected.

I can't find any other fault apart from that switch problem. I've trawled the forums and checked everything else that other people have said it could be when they've had the same problem.

Any help would be much appreciated.

Jon
October 2014