Testing Sending Unit Potentiometers

[snakedoc67]

Just looked thru the DIY post of refurbishing the fuel sending units. Can anyone tell me the proper way to test the potentiometers? I am reinstalling my sending unit today and would like to verify its good while i have it out and to test the one from the parts truck. 

[HOrnbrod]

The test is to verify the sending unit's potentiometer (pot) is picking off the correct ohm values (resistance) as the float arm moves the pot's slider from full-to-empty fuel conditions. These values directly impact the fuel gauge needle deflection. To test, connect an ohmmeter across the pot's center terminal that goes to the gauge and the slider terminal that is tied to the float. Move the float slowly up and down. The ohms readings are checked at full, empty, and all points in between. It's best to used an analog ohmmeter for testing to verify a smooth transition and that there are no dead spots along the pot's windings. The ohms resistance readings should correspond to the values stated in the vehicle's FSM. Renix and HO senders have different resistance values and the output polarity is opposite, but the testing process is the same for both units.

[snakedoc67]

thanks, didnt think i'd get a reply that quick. lol

[cruiser54]

Hang on for a bit. We'll likely soon get a complete term paper on the evolution of sending units.......

[jeepsouth]

HA! I was thinking the same thing!

[cruiser54]

So far the waters haven't been muddied. We should all be thankful for that!!!