Water Temp Gauge Not working

My Engine Water temp gauge is

My Engine Water temp gauge is not working? Can the Gauge be checked or tested to see if it is working or a test to check the sending unit?

Thanks
John

What engine and year? W/the i

What engine and year? W/the ignition switch in the RUN position ground the sender unit wire. If the gauge pegs to the max then it works. It's either the sending unit or more likely the thermostat not closing.

If the gauge does not move then check the wire connections on the backside for corrosion.

Thanks

1994 Sea Ray 25 foot

Thanks

1994 Sea Ray 25 foot- 7.4L Mercrusier Bravo 1

I have pulled the gauge already can I check using a 12V tricle charger-- Hook up to I and S on the back of the gauge?

Use a 9 volt battery; negative

Use a 9 volt battery; negative to the ground and positive to I or S.

"Sending unit is a variable re

"Sending unit is a variable resistor. ~ 80 - 240 ohms.

Do NOT hook the battery + lead to the S terminal.

The S termnal is the connection to the sending unit.

Battery power is only to power the guage.

Connect a ohm meter, one lead to the center terminal on the sending unit and the other lead to the threads.

What ohm reading do you get?

Next put a small pot of water n the stove and submerg the sending unit ( just the end portion of the sending unit that makes contact with water) and turn the heat on the pot.

watch the ohm meter. the reading should change as the temp increases. Waych carefully to see if it is gradual. if it jumps a great deal from say 180 ohms to 100 ohms with a very small change in water temp. the sender is bad. If the ohms change steady and gradually then the gauge is bad.

Of course you have checked the wiring in the boat first????"

Thanks for the advice - Looks

Thanks for the advice - Looks like the gauge is bad- no movement of needle when tested-- So I found a old water temp gauge and it works-

Apprecite the help as its all good