Re: Yanmar 4jh3-hte overheat

Mark McGovern


Generally, temp sensors work off of resistance with high resistance when cold and much lower resistance as the medium gets hotter.  You can use a cup of room temperature water and boiling water and measure the resistance across the wires of the sensor and see if there is any difference.  However, you would need the actual specifications on the Yanmar temperature sending unit to test it definitively and make sure it is working properly.  I suppose you could buy a new sensor, test it the same way and compare the results to the old sensor.  If the results are similar you could assume that the old sensor is working properly.

A few Amel owners have taken to installing a secondary separate Exhaust Temperature sensor and alarm.  You can read about it here:,,,20,0,0,0::Created,,muffler+melt,20,2,0,29759579
Mark McGovern
SM #440 Cara
Deale, MD USA

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