1950 239 flatheat water temperature sending units

1

1950 custom

Junior Member
I would think most here know theses flatheads have two temperature sending units. One with one terminal and the other with two terminals. I know the one with two terminals is strickly an on-off switch. The one terminal actually controls the temperature gauge by I think changing the resistance. My questions are
1. What is the temperature at which the two terminal switch closes and gives a ground to the circuit causing the gauge to move to hot?
2. At what temperature will it switch back?
3. Is there a resistance chart vs temperature for the one terminal sending unit that causes the gauge to move?
 
First of all, you should know that Ford gauges do not use variable resistance. They operate on the "King-Seely" principle, which uses bi-metallic actuators in the sending unit that sends different pulses to the gauge that has a corresponding bi-metallic unit in the gauge that causes the gauge to register the reading.

A short search on the internet says the dual terminal gauge closes at 220 F. I would imagine that that it may vary between units, but it sounds about right.
 
I will try to do some research on that. I didnt think it would be like a thermistor that changes resistance based on temperature where there is a specific resistance for each degree. I could see a resistance change in the unit but it was quickly changing.
Thanks for the information.
Do you know the normal operating temperature with 180 degree thermostat? I am guessing somewhere between 180 and 190?
 
I'm looking to buy a single or double sending unit for a 49 to 53 that doesn't cost an arm and a leg.. Tell me what you have. Used is just fine. Thanks.
 
I think I have a bunch in a coffee can. I'll look the next time I'm at my shop. Exactly what are you trying to do and what do you actually need?
 
Last edited:
You must log in or register to reply here.
Back
Top