First 1991 f-350 7.3 motor. What is the 2 prong sensor called that is threaded into the right side head next to the thermostat housing.

 

I know the cold start switch is in that general area, it has two terminals. Power comes in on one side, and below about 70* the switch closes, sending power to the high idle and cold advance solenoids.

 

Uh, can you take a picture? I don't recall what you're thinking of.

I know there's two sensors on the /driver/'s side, which are the thermostat gauge and overheat 'idiot light' switch sensors, but both of these are, IIRC, one terminal.
(you can tell which is which by disconnecting one, then the other, and see which moves your gauge).

Edit:
Hm, Ford_six makes sense.
70F seems a bit low, though, probably more like 150F...

 

^^^What he said:


https://www.ford-trucks.com/forums/1...l#post13494405

 

Cold start switch anybody know where to buy one mine has a terminal missing. Part number?

 

K Ive gotta.... I shall name thee Fred

so whats next?

 

Cold start switch 1803082C2 (E8TZ9E939A)
Water temp switch E3TF-10B843-AA (244*F)
Water temp sender DOZZ10884A (sw-925) <!-- / message -->

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