King seely sending unit ?

Which one? They were used in fuel quantity, coolant temp, and oil pressure indicating systems. The 1949 through 51 Lincoln Mercury Overhaul Manual is the best book to have on the subject.
 
Can't you use an ohm meter to test it? Put the voltmeter on OHMs, put the positive lead on the sending unit screw hole and the negative lead on the body of the sender. Move the arm and watch the OHMs go up and down.
 
You can't verify function of a KS sending unit as they don't use the Ohms principle.

I bought a NOS fuel gauge at a swap meet and made an easy fixture to verify my sender. Here is a link to the You Tube video. https://www.youtube.com/watch?v=cB1PkY55NeY

You can test in the car by removing the sender and hooking up the sender wire and a ground. If you chose to do this near the fuel tank block off the sender hole and make there are no sparks that will ignite the fuel fumes!!!!
 
Dan has a good point on sparks around the open fuel tank. Also, disconnect the power to the ignition coil while testing with the key on, as leaving the key in the ON position can damage the coil/points if the engine is not running.
 
Is the 49 fuel sending unit that much different than a 40? Because I just successfully tested a nos 40 sending unit with an OMHs meter.
 
KS units have a bi-metallic switch with a little set of points. The top cover pops off with a little prying and the points can be cleaned. Many times this is all that is needed to restore function. The indicator also has a bi-metallic actuator arm to make it move. More current more movement.
 
Dan in MI said:
Seth, the 40 and 49 sending units are the same except for the float arms. If you use an Ohm meter to check it you will get values or no value if there is an open. Since the KS sending units don't function on Ohms principle (uses pulse rate) there is no correct upper/lower values.

Here is a link to a discussion about the senders: https://www.fordbarn.com/forum/showthread.php?t=165773&highlight=King+seely&showall=1
Click to expand...

So if you move the arm up and down with an OHM meter attached and the ohms values increase and decrease, would it not indicate the sending unit if functioning?
 
Yes but are the values correct? How do you know if the value you get will correspond with the right reading on the fuel gauge?
 
The bottom line is that an OHM Meter will not give accurate readings as the the accuracy of the operation operation of the KS fuel tank sending unit.
 
When you move the float arm on the King Seeley sender, all you are moving is the bi-metallic strip in the sender and it's not moving so much as it is having pressure applied to it. This changes the pulse rate that the points open and close at. Slower pulse rate, more current flow. Faster pulse rate, less current flow. The indicator in the panel only reads out the current flow it gets from the sender.

There is a resistor in most of these type sending units but it is for calibration since it is a fixed resistance and not a potentiometer like more modern senders use. The King Seeley system had no electrical components exposed to the fuel in the tank and had no wear points other than the little pulse breaker points. Modern potentiometer based fuel quantity senders start to wear on day one and eventually the little brush or the resistor wire wears out. They are cheaper to produce but don't last as long.
 
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