Yanmar 2GM20F - temp sensor keep buzzing after engine being rebuilt

[Wotname]

^^

You probably have another version of the B type panel, an earlier one I guessing. I have found a circuit for a B panel with the light switch as you have described.

Quick question, does your panel have a key switch and then a push button to start the engine or is the start switch part of the key switch (like a car)?

Either way, I will get back to this problem in a few hours when I get home and have some more time to think about what you have posted above.

I'm sure the end is in sight

[Wotname]

This looks like your panel
http://farm7.static.flickr.com/6192/...b32ab45189.jpg

[Wotname]

This looks like your panel
http://farm7.static.flickr.com/6192/...b32ab45189.jpg

Mine is somewhat different but let's deal with your one.

The light switch is as you describe, one position turns on the lamp in the tacho and the other position (momently) turns on the temperature light and the buzzer.

Please note the buzzer has 4 wires. A red/black which is the +ve that comes from the key switch and three -ve wires, one for the temperature alarm, one for the low oil pressure alarm and one for the spare lamp. So the isolation of the three wires occurs inside the buzzer (presumably with some diodes).

Maybe the best option is first find out if the fault is contained in the console or if it is in the rest of the loom. Given what you have already posted, I will guess it is console wiring (and/or buzzer) rather than the rest of the loom.

So my suggestion is to unplug the console and temporarily connect +ve and -ve to it. Put the +ve on the red wire (that ends up on terminal 30 of the key switch) and put the -ve on the black wire (that ends up going to -ve on the tacho, the tacho lamp and to light switch).

If the console is OK, nothing will happen at this point.

Now turn on the key switch; again if the console is OK, nothing will happen but if the buzzer sounds and the temperature light comes on, then the console is faulty somewhere. More about that below.

Assuming that nothing happened when you turned on the key switch, then you have to test that you have temporarily connected it properly. Do this by trying the light switch. One way will light the taco light and the other way (momentary) will sound the buzzer and light the temperature light. If this is the case, you have connected it correctly.

Last test is to test the isolation in the 3 -ve buzzer wires. One way is to connect a -ve lead to individually each of the -ve wires on the buzzer. In each case, the buzzer should sound and only one corresponding light will turn on . If more than one light comes on, either the buzzer is faulty inside or the lamp wiring in the console is faulty.

I do hope this is not too complicated. It is hard to write everything out exactly and I don't know how much you understand electrical testing. There are many other ways to test it with a meter but again, it becomes hard to explain if you are not used to reading meters.


Enough for now, do let us know how it works out and ask more questions if you wish.