1940 Ford temperature sensor diagram

[Joseph P. Indusi]

I am trying to help out a friend who has a 1940 Deluxe V-8 Ford.   The wiring diagrams show a very odd arrangement for the temperature, oil pressure and one other sensor.   They include a resistor and what looks like the symbol for a bi-metallic switch with a heater wire around the bi-metallic section.   I cannot understand how this works and I have seen two different versions of the sensor wiring diagram.   Does anyone on this forum know the theory of how this type of sensor wroks?

Thanks.

Joe

[19tom40]

Here is a link to a discussion on the theory behind these gauges. Basically both the sending unit and the dash unit have heated bi-metal switch. The current flow in the circuit moves the needle on the dash unit to indicate the oil pressure, fuel level or coolant temperature. This system provides a more accurate measurement than the variable resister units used in other vehicles.

 

https://www.fordbarn.com/forum/showthread.php?t=165773

[Joseph P. Indusi]

Many thanks for directing me to this site.  This is a very complete description of these sytems.

Joe