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Old 13-03-2018, 13:44   #1
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Yanmar Idiot lights

Hi all,

Can not seem to find anything on this, and car information seemslikely not to be transferable

Yanmar 2GM, 1982, 1200 hours, well serviced.

I was running across Biscayne at night when all three of the idiot lights and the alarm sounded at the same time. I shut the engine down promptly to idle speed and checked:

1. Exhaust water expelling, cooling system belts operating, so no issue with the cooling system

2. Oil level OK, nothing in bilge, no obvious leaks

3. I am not sure what the third light is, but it was on


If I turn the key off, the engine continues to operate....the lights go out...and the charge light comes on. (presumably because the alternator is spinning but not charging if the key is off??)

When I restarted, the lights did not come on and normal operation seemed like the right way forward. After about 10 minutes, the lights and buzzer came back again simultaneously.

I proceeded ahead at half throttle with the key in the off position for about 30 minutes....switched off again....restarted. No lights, and then again they simultaneouosly came back on in about 10 minutes. I stopped for the night.

In the morning, it started normally and again after 10 minutes, all lights and alarm on. When I turned it off and restarted, they stay on. When I shut down for 30 minutes and made coffee, they were off again, but came on after 10 minutes or so.

I proceeded home for approx two hours with key in off position.

Any ideas as to why all three lights would give a simultaneous false positive?

Thanks for any input!!
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Old 13-03-2018, 14:02   #2
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Re: Yanmar Idiot lights

Quote:
Originally Posted by Rocinante33 View Post
Hi all,

Can not seem to find anything on this, and car information seemslikely not to be transferable

Yanmar 2GM, 1982, 1200 hours, well serviced.

I was running across Biscayne at night when all three of the idiot lights and the alarm sounded at the same time. I shut the engine down promptly to idle speed and checked:

1. Exhaust water expelling, cooling system belts operating, so no issue with the cooling system

2. Oil level OK, nothing in bilge, no obvious leaks

3. I am not sure what the third light is, but it was on


If I turn the key off, the engine continues to operate....the lights go out...and the charge light comes on. (presumably because the alternator is spinning but not charging if the key is off??)

When I restarted, the lights did not come on and normal operation seemed like the right way forward. After about 10 minutes, the lights and buzzer came back again simultaneously.

I proceeded ahead at half throttle with the key in the off position for about 30 minutes....switched off again....restarted. No lights, and then again they simultaneouosly came back on in about 10 minutes. I stopped for the night.

In the morning, it started normally and again after 10 minutes, all lights and alarm on. When I turned it off and restarted, they stay on. When I shut down for 30 minutes and made coffee, they were off again, but came on after 10 minutes or so.

I proceeded home for approx two hours with key in off position.

Any ideas as to why all three lights would give a simultaneous false positive?

Thanks for any input!!
If your GM is anything like my 2QM20 the third light is the alternator sensor - if it goes on, you ain't charging.

The fact that all three came on at once suggests an electrical short somewhere, probably at one of those shitty plastic plugs that yanmar liked to use as part of the harness...
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Old 13-03-2018, 14:21   #3
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Re: Yanmar Idiot lights

They all are separate circuits really and the only place they are close to each other is at the wire harness plug. I bet there’s water getting on yours
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Old 13-03-2018, 14:45   #4
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Re: Yanmar Idiot lights

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Originally Posted by sailorboy1 View Post
They all are separate circuits really and the only place they are close to each other is at the wire harness plug. I bet there’s water getting on yours
The buzzer as well, same buzzer used for all three alarms separated by diodes.
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Old 13-03-2018, 14:52   #5
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Re: Yanmar Idiot lights

wiring diagram....
Attached Files
File Type: pdf 3GM30-pg15.pdf (58.1 KB, 41 views)
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Old 13-03-2018, 15:06   #6
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Re: Yanmar Idiot lights

If you turn the key off while running on some boats you blow the diodes in your alternator.
Sounds like a connector issue.
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Old 13-03-2018, 15:27   #7
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Re: Yanmar Idiot lights

Quote:
Originally Posted by sailorboy1 View Post
They all are separate circuits really and the only place they are close to each other is at the wire harness plug. I bet there’s water getting on yours
Yes, this is the first place I would look at, especially if you have some corrosion built up there after 35 years of operation.

Quote:
Originally Posted by Cheechako View Post
If you turn the key off while running on some boats you blow the diodes in your alternator.
Sounds like a connector issue.
FWIW, this isn't an issue if the the OP's 2GM still has the original wiring arrangement. Turning the key off will disable the regulator / field wiring, not the output diodes etc.
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Old 13-03-2018, 19:12   #8
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Re: Yanmar Idiot lights

Do these lights come on momentarily during start up, as they would in a car? If so you may have a bad starter switch or perhaps an associated relay.

When it fails (lights up) giggle the switch or smack it with you hand and see if that changes things.

I’m guessing there is a momentary “light test” circuit and that is somehow being activated.
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Old 14-03-2018, 02:19   #9
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Re: Yanmar Idiot lights

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Originally Posted by hpeer View Post
Do these lights come on momentarily during start up, as they would in a car? If so you may have a bad starter switch or perhaps an associated relay.

When it fails (lights up) giggle the switch or smack it with you hand and see if that changes things.

I’m guessing there is a momentary “light test” circuit and that is somehow being activated.
The correct operation of the Yanmar GM idiot lights are as follows:

The low oil pressure and charge lights illuminates when the key is turned on. The buzzer also sounds.

These stay on until the engine starts and oil pressure rises and the alternator spins up.

The over temp. light does not illuminate at start up.

There is no light test circuit as such.
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Old 15-03-2018, 09:52   #10
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Re: Yanmar Idiot lights

No they do not.

When I turn the key on but before I push the starter, all four lights plus the alarm come on. Always have. I have always assumed that this was to indicate that all of the warning circuits are operable (??)
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Old 15-03-2018, 10:10   #11
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Re: Yanmar Idiot lights

Yanmar isn't the only builder/engine that used those dumb harness connectors. That is where to start. Good luck.
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Old 15-03-2018, 11:06   #12
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Re: Yanmar Idiot lights

Quote:
Originally Posted by Rocinante33 View Post
No they do not.

When I turn the key on but before I push the starter, all four lights plus the alarm come on. Always have. I have always assumed that this was to indicate that all of the warning circuits are operable (??)
A. Then your wiring diagram does not match the one above
B. Your problem is in that switch or an associated relay.

Good luck.
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Old 15-03-2018, 16:10   #13
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Re: Yanmar Idiot lights

Quote:
Originally Posted by Rocinante33 View Post
No they do not.

When I turn the key on but before I push the starter, all four lights plus the alarm come on. Always have. I have always assumed that this was to indicate that all of the warning circuits are operable (??)
Quote:
Originally Posted by hpeer View Post
A. Then your wiring diagram does not match the one above
B. Your problem is in that switch or an associated relay.

Good luck.
Hpeer is correct, it is highly unlikely that your engine is wired in accordance with the original Yanmar wiring harness. I have yet to see any older Yanmar (GM, YS, S series etc) have a self test arrangement for the idiot lights. This has been poor Yanmar design aspect IMO, especially for the over temperature alarm as neither the light or the sender is tested for serviceable condition. At least the low oil pressure is tested simply by it's nature - no oil pressure before engine start!

I suspect that someone has modified the original wiring to incorporate a "test on start up" feature and as hpeer suggests, this is most likely a relay. At least that is how I would do it .

A small confusion though, in the OP, you state you have three idiot lights and now you are saying four??? Not that matters so much but are they all in a standard Yanmar panel or in a custom panel? Any chance of a pic of the panel?
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Old 15-03-2018, 16:44   #14
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Re: Yanmar Idiot lights

Had somewhat of a similar problem with the 1GM harness on my boat (basically the same as the 2GM harness). Had an over-temp condition (failed impeller) and all alarms went off. Once the problem was taken care of everything worked normally...or appeared too.

If you look at the wiring harness schematic, all of the alarms use a common ground (-) connection. These are isolated from each other by diodes located in the wiring behind the engine control panel. I found that all but alternator diode was shorted, basically connecting all of the idiot lights together in a single circuit.

Check the diodes behind the engine control panel. Additionally, ensure that the over-temp and oil pressure sensors are clean and free of moisture/oil as, if they are dirty, they create a low resistance path to ground (-) and will also give a false alarm indication (or in some cases when "not quite" an alarm condition, an annoying low volume buzzing of the alarm annunciator).

Just my 2-cents worth from my own experiences. And yes, crappy plugs don't help...make sure they are clean, dry, and sealed with at least electrical tape.

Good Luck!
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Old 15-03-2018, 17:01   #15
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Re: Yanmar Idiot lights

You might try Googleing the shop manual for the Yanmar 2gm. Perhaps, http://www.jeanneau-owners.com/Manua...e%20Manual.pdf . Take a look at pages 12-2 and 12-3. There are two possible instrument panels. Look and see which one is yours. One has an instrument test switch; one does not. In any case, a wiring diagram is your friend. That and a VOM meter will find your problem.
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