Question: Testing water sending unit

[BLK VERT]

Hi, How do you test the water sending unit? I heard with an ohm meter. Do you touch the body with one lead and the tip with the other lead? Tony

 

[Vette79]

Doing what you suggested will/should give you the correct ohm rating of the sending unit.

 

[wishuwerehere82]

Inside the temp sender is a device called a Thermistor.
It is a temperature variable resistor and changes its resistance with change in temperature.
In ice water(32degrees F/ 0 degrees C) it will have one resistance and in boiling water(212 degrees F/ 100 degrees C) it will have another. One being higher and the other lower, not sure which.
You can measure it with an Ohm meter between the base and terminal on older units, or between the two terminals on the newer units.
Just clip your meter leads onto it and put the metal part into the water. You will see the resistance value change as it reads the temperature of the water.
You should see a linear slope on the resistance change between the ice water and boiling water. If at any point it goes to 0 Ohms(shorted) or infinite ohms(open) the thermistor is damaged or the contacts are broken to it.

You can test it in the engine block without going through the ice water test by testing it when the block is cool and then again when it's hot to see if there's a change in resistance.

 

[JohnZ]

Here's the temperature/resistance curve for the 1513321 sending unit used in midyears; I think the C3 units are similar.