How do you test a marine temp sending unit?

Disconnect the wire from the sender terminal. Set your volt-ohm meter to the 1K ohm scale. Measure the resistance between the sender terminal and the engine ground. The temperature sender is faulty if the resistance measures 0 ohms when the engine is cold, or if the resistance is infinite or open.

How do you troubleshoot a temperature sensor?

Troubleshooting a faulty temperature sensor steps:

1. Check -ve and +ve leads are correct.
2. Check you are using the correct type of cable.
3. Check for local heat sources affecting your readings.
4. Check setup of your temperature controller/readout.
5. Resolve out of range errors.
6. Resolve Sensor Break/Open circuit errors.

How does a water temperature sending unit work?

The sending unit is a temperature-sensitive material that is part of a variable resistance, water-sealed unit that sits in the coolant stream in the engine. As the engine warms up the resistance in the sending unit is lowered gradually until the system reaches maximum heat.

Is the temp sending unit good or bad?

The original Sending unit appears to be bad. No readings from it Hot or Cold. The newer one gave me some screwy readings. At room temperature the new one shows 52 Ohms, at 210 degrees it shows 8 Ohms. It should go the other way. I wonder if this is a bad part or I have the wrong one of these as well. Have to go to Plan B now.

What does it mean when temp goes down on auto thermistor?

The auto thermistors I’ve worked with all tended to be NTC (Negative Temperature Coefficient, as opposed to Positive Temperature Coefficient) devices, so if the resistance goes down as the temp goes up, that sounds right (an open in the temp gauge circuit typically shows a cold temperature, not a hot temperature).

How big is a Chevy water temp sender?

You could also boil some water on the stove or microwave and drop it in for a few minutes, then test the resistance again. I remember from looking in the part store catalogs that a chevy water temp sender sould be around 80 Ohms at 100 Deg and 180 Ohms at 220 Deg.

The original Sending unit appears to be bad. No readings from it Hot or Cold. The newer one gave me some screwy readings. At room temperature the new one shows 52 Ohms, at 210 degrees it shows 8 Ohms. It should go the other way. I wonder if this is a bad part or I have the wrong one of these as well. Have to go to Plan B now.

The auto thermistors I’ve worked with all tended to be NTC (Negative Temperature Coefficient, as opposed to Positive Temperature Coefficient) devices, so if the resistance goes down as the temp goes up, that sounds right (an open in the temp gauge circuit typically shows a cold temperature, not a hot temperature).

You could also boil some water on the stove or microwave and drop it in for a few minutes, then test the resistance again. I remember from looking in the part store catalogs that a chevy water temp sender sould be around 80 Ohms at 100 Deg and 180 Ohms at 220 Deg.