Water Temp Sensor Trouble shooting

[Dale I]

I have a Yanmar ignition panel on my 2gm that has 3 lites, (Water-Oil-Charge), and the oil and charge lights light up and the alarm sounds when the ignition key is turned on, (as they should without the motor running). My question is, should the water temp light come on then as a 'test' even though the motor isn't operating? How do you know otherwise if it is defective or the bulb is burnt out? Can I test it someway?

 

[Bill O'Donovan]

Doesn't matter

Just check your coolant monthly and look for any leaks at the various hose connections. Don't put much faith in the overflow bowl, though. It's a crock. Check at the cap.

 

[Jeff M21319]

Not real familiar with the Yanmar 2gm but...

generally speaking, a temperature sensor on a motor is a 'normally open' type switch that only closes when it's temp exceeds the set point. With the ignition ON you should be able to remove the wire from the sensor and ground it to the motor to test the bulb and wiring, but this won't tell you if the sensor is functional. IMHO, I don't really like 'idiot lights' because they only tell you that something has ALREADY gone wrong. I'd much prefer to have oil pressure and temp GUAGES so that I can see what is really happening and if something is STARTING to go wrong. It wouldn't cost that much to add guages and they might just save you a lot of trouble and money down the road!

 

[Ed Bergman]

Nope

Your water temp light should not activate until the engine overheats. Your other two lights come on because until the engine is running, you have no oil pressure or altenator output. On mine I have a test switch that will light up everything and sound the alarm when the engine is running.

 

[Dale I]

Jeff M, ....My mistake, its a 2QM20H

...Which is raw-water cooled. Fortunately, we don't have a great deal of grass/weeds in the St.Johns River to suck in. Generally, we have only soft growth in the brackish water to deal with. Guages ARE ON the to-do list...and will be done at the speed of money and time.Thanks for your input, all.