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Old 12-03-2012, 07:25   #1
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Troubleshooting Yanmar 3GMD Instruments.

It is not a good thing, but I have been running my engine with with limited instrumentation. Now, troubleshooting these circuits has now come back to the top of my to-do list.
In the beginning: Judging by the re-configuration of the wiring, the PO has tried to change / upgrade the oil pressure and the engine temperature circuits. From the drawings I have, the original sensors for both the oil pressure and temp were probably on/off switch type sensors used to activate the alarm annunciator. With these sensors, there were probably no display gauges.
What I have now: Both the oil pressure and temp sensors have analog outputs to drive their respective meter gauges.
-Oil Pressure.. The oil pressure gauge operates as expected, but the alarm annunciator does not sound when the oil pressure is low.
-Temperature.. The temp display barely comes on scale when the engine is at operating temperature.
What I have found so far:
-The annunciator is BAD. The alarm will not sound when activated from any of the input sources. I need to find a replacement annunciator.
-The voltage across the temp sensor changes as the engine warms; Thus, it appears to be good. (The thermostat has already been changed.. no help.)
-I am not sure if the temp display is even the correct one for this application.
The engine is a raw water cooled YANMAR 3GMD. The thermostat opens at about 135F, so it is a cool running engine. It would help if I knew the typical full-scale operating current for the temp display gauge. At least then I could set up a test circuit to check the meter movement.
Any suggestions on where I might find a used annunciator (The engine is 30 years old.) or for additional troubleshooting checks will be appreciated.
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Old 12-03-2012, 07:48   #2
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Re: Troubleshooting Yanmar 3GMD Instruments.

Here are 3 charts that should help you out..........
Notice the difference between USA and Euro readings. Yanmar may have both. Go by the pipe thread. My Yanmar oil gauge was Euro and the water is USA, from the factory.

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Old 12-03-2012, 08:43   #3
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Re: Troubleshooting Yanmar 3GMD Instruments.

Dellmarrey, Thanks for the info and drawings. Though, thanks to the PO, the color code is not the same, this will give me some parameters to help in the troubleshooting.
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