Temperature gauge problems

[brandonstc]

I have a 1949 ford f1 with a flathead 6. I got the truck running, but my temperature gauge doesn't work. When the key is off, the gauge reads hot. When the key is on, the gauge always reads cold. The temperature sending unit has only one screw on it and there are two wires coming out of it. The blue wire goes to the gauge and the purple wire is the power wire. It seems like the wires are basically just tied together, bypassing the sending unit. The truck was converted to 12v years ago and the wiring was done by the original owner. How is it supposed to be wired. Any help would be appreciated. I have included a picture of the sending unit and the source of the power wire.

 

[RMR&C]

Power should go to one side of the gauge and a single wire from the other side to the sender. Is that a voltage reducer in the pic or?
Also it's normal for the gauge to show hot with no power.

 

[TerryOH]

RMR&C has it correct. The Temp. gauge does read high when there is no power and will go toward cold when first power up. then moves to engine temp.

 

[41ford1]

the attached diagram shows how the gauge is wired and how it works. you will need to reduce the 12 volts to 6 at the power to the gauge unit. You can do that with a Runtz reducer or a late '50s Ford gauge voltage regulator.

the 2 post sensor unit is for V8 only. The sixes use the 1 post.