Yanmar 3YM20, warning instrument fuses

charles_reed

charles_reed

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After a fairly long windward thrash, during which the motor had to be used frequently, I discover that the coolant, exhaust, oil-pressure lights and siren alarm are all coyly hiding.
The engine starts and runs normally (just doesn't squeal).
I've checked the small blade fuse, behind the instrument panel, for continuity and that's OK.
All the sender terminals are on and good.

Obviously the highest probability is a blown fuse - but where is it in the harness?

I'm stuck here on Skyros until Wednesday (and there's no Yanmar engineer on the island), so plenty of time to deal with the problem.
 
charles_reed said:
After a fairly long windward thrash, during which the motor had to be used frequently, I discover that the coolant, exhaust, oil-pressure lights and siren alarm are all coyly hiding.
The engine starts and runs normally (just doesn't squeal).
I've checked the small blade fuse, behind the instrument panel, for continuity and that's OK.
All the sender terminals are on and good.

Obviously the highest probability is a blown fuse - but where is it in the harness?

I'm stuck here on Skyros until Wednesday (and there's no Yanmar engineer on the island), so plenty of time to deal with the problem.
Click to expand...

I wonder if they are all supplied through the buzzer and the buzzer has blown which has isolated all the lights?

Can you disconnect one of the wires to the buzzer and then check the resistance across the buzzer terminals? If the resistance is open circuit I would think that is the problem.

Richard
 
charles_reed said:
After a fairly long windward thrash, during which the motor had to be used frequently, I discover that the coolant, exhaust, oil-pressure lights and siren alarm are all coyly hiding.
The engine starts and runs normally (just doesn't squeal).
I've checked the small blade fuse, behind the instrument panel, for continuity and that's OK.
All the sender terminals are on and good.

Obviously the highest probability is a blown fuse - but where is it in the harness?

I'm stuck here on Skyros until Wednesday (and there's no Yanmar engineer on the island), so plenty of time to deal with the problem.
Click to expand...

The only fuse shown in the wiring diagram in the w/shop manual is the 3 amp one in the instrument panel. http://www.motoren.ath.cx/Download.php?filename=/yanmar/3ym-2ym-service-manual.pdf

If there was a failure of the supply to the panel nothing controlled by the key switch would work.

Its difficult to see that the fault will be anywhere other than in the panel, and in the supply to the warning lights and buzzer from the key switch at that. The fuse is the obvious suspect.

If the buzzer were to fail open circuit the buzzer would not wok but all the warning lights should.
 
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I've checked the buzzer terminals - when the switch is on there's full 13.5 volts going through, two terminals are +ve one -ve. Having checked the fuse for continuity and found it good (borne out by the volts to the buzzer terminal), I'm at a loss.
Thanks though for the input - that which disappears may come back!!
Wishful thinking - I've got 131nm to do Wed night to Saturday midnite whilst there's no meltemi and favourable Bf 3/4s
 
charles_reed said:
I've checked the buzzer terminals - when the switch is on there's full 13.5 volts going through, two terminals are +ve one -ve. Having checked the fuse for continuity and found it good (borne out by the volts to the buzzer terminal), I'm at a loss.
Thanks though for the input - that which disappears may come back!!
Wishful thinking - I've got 131nm to do Wed night to Saturday midnite whilst there's no meltemi and favourable Bf 3/4s
Click to expand...

If you checked with a digital multimeter its worth also double checking with a test lamp ( couple of leads soldered on to 12 volt bulb) Digital meters draw so little current that they can often make a fool of you by giving a normal reading through a bad connection. A bulb however draws some real current,
 
I don't know how well you can see the back of the panel but check that none of the plugs have come off the connections at the back. Easy to miss if it's not very accessable. I had a similar fault some time ago when I knocked off a plug when I put my dinghy oars away in the locker and caught them on the wiring at the back of the panel. The engine still started ok but I lost the instrments display.
 
You need to get a wiring diagram and check for common points. On the 2gm 20 each sender/switch and bulb is separate and the common point is the buzzer and feed to it. I'm not sure about the 3ym but suspect it might be the same. You need the buzzer in the cct to allow the bulbs to light up.
The switches on the sensors ( oil and water) make and create the cct through the buzzer to earth at the sensor switches. An Open cct buzzer or no feed to the buzzer would cause the bulbs not to light.
When you say you have 13v at the buzzer are you testing across the buzzer with a volt meter? That would suggest to me it is open cct. Disconnct the wires at the buzzer. You should have +13v on one side and an earth on the other if the ignition is on and the engine not running.
Apply an earth on the neg side of the buzzer if it sounds that will prove all wiring up to the buzzer is ok. If not you are looking at a faulty buzzer.
 
Spyro said:
You need to get a wiring diagram and check for common points. On the 2gm 20 each sender/switch and bulb is separate and the common point is the buzzer and feed to it. I'm not sure about the 3ym but suspect it might be the same. You need the buzzer in the cct to allow the bulbs to light up.
Click to expand...

Your description seems very different to the wiring digram shown for the 3YM20 in the manual I gave the link for in post #3: http://www.motoren.ath.cx/Download.php?filename=/yanmar/3ym-2ym-service-manual.pdf

 
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