My bis fan kicks in at half way on the gauge... pretty much as soon as the thermostat actually opens (keep feeling the bottom rad hose... stays cold for quite a while at idle, holding rpm up higher helps but load on the engine will increase the temperatures quicker. There should be two speeds Gadge, so i'm wondering if yours is only operating on the "high speed", you can check the fan by bridging the pins on the coolant switch (which is on the far side of the rad) or applying 12v direct to it... the connector had snapped off on mine from corrosion... managed to come up with a solution as it was the ground pin that had broken off and the rivet that holds it all together inside was also ground... Had a spare connector from an aircooled condensor so managed to screw that into the rivet with a crimped "o" connector on the end and could plug the ground of the main power feed back in no problem!
Hope things with your float switch are getting better now!?
The bodywork on that lovely white bis looks great and that new carpet looks great too!
Only just stumbled upon this thread, been refurbishing the steels I bought from you the past few days! Going to get some paint on them tomorrow if the weather allows!