just some thoughts when i read this question .......
engine (head) water sensor:
I have no fan blade run off the pulley.
when i installed my new water temperature thermostat sensor in the head I was sold a newer sensor which is the replacement for my old. this newer sensor has a smaller pipe thread, so i had to use an adapter bush to reduce the 3/4' to 1/2''. Because of this i ended up chucking the bushing on my lathe and shaving off some threads and also cutting a couple more threads on to the new sensor. this now allows me to thread the new sensor further into the bush and now allows the water @ the head (temp) to reach the flow of water that flows past it to get a better reading on my gauge. if i did not do this a false sensor reading happens in that 'dead zone' around the reducer bushing because of the reduced (lack of) water flow. this senses the temp in the block, the blocks temp trips the stat to open.
fan sensor::
i put my pusher fan's thermostat sensor on the lower side of the thermostat housing , below the thermostat, along w/ the water to my carb-(tap ... split intake and exhaust systems) and the water to the cab's heater-(tap). so i had to drill an extra hole because my two available ports were used. I have recently seen the inserted into the radiator fins sensor, and that's worth some investigation.
i know this may not be the case w/ you Tex but others may read this thread and it may give raise to some thought.
i also am using two relays to power my pusher fan because of the greater amount of draw during fan start up mode. the fan can run easily on one relay but that start is what might kill your systems fan. you will also have a higher temp reading at idle and after you stop the engine. that gauge will rise just a bit, which is normal because of the no air flow mode.
When selecting a fan switch, seems The Fan Man Switch kit works great. For a 160º thermostat, use an 185º or 195º switch. For an 180º thermostat, use a 195º switch. For a 195º thermostat, use a 210º switch.
