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Old 27-12-2019, 10:58   #1
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3ym20 Yanmar instrument panel start button won't start

Here is description of my issue that happens during start up process....

Press power button. LCD readout displays. Engine check icons light. Buzzer sounds. Press start...everything turns off (buzzer stops and panel power turns off).

New batteries are charged. Oil changed three weeks ago.

Can I replace just the start switch? Or does entire switch panel need replacing?
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Old 27-12-2019, 11:07   #2
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Re: 3ym20 Yanmar instrument panel start button won't start

It is most likely a bad connection in the wiring harness or relay feeding the power to the panel. Trace your plus/minus power wires, clean and tighten every connection point in the harness.
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Old 27-12-2019, 11:08   #3
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Re: 3ym20 Yanmar instrument panel start button won't start

1st guess. Bad ground.
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Old 27-12-2019, 11:13   #4
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Re: 3ym20 Yanmar instrument panel start button won't start

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1st guess. Bad ground.
I am a total neophyte about electrical systems. I assume a local ground connection to the panel needs to be cleaned?
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Old 27-12-2019, 11:16   #5
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Re: 3ym20 Yanmar instrument panel start button won't start

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It is most likely a bad connection in the wiring harness or relay feeding the power to the panel. Trace your plus/minus power wires, clean and tighten every connection point in the harness.
Thanks. How would I trace a wire through a wire harness?
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Old 27-12-2019, 11:31   #6
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Re: 3ym20 Yanmar instrument panel start button won't start

Could be anywhere, and could, as DF suggests, be on either side (+ or -). Start with what's easiest, but work methodically.

My first check would be the main power connections at the batteries and the engine, and then the wiring harness at the instrument panel.

Depending on the age and the environment the wiring has experienced, sometimes just wiggling the wires can isolate the offending circuit, as can disconnecting and reconnecting any accessible wire connectors. In an old installation, it can often be helpful to dissassemble and clean all relevant connections; though this is time consuming, it can sometimes eliminate a host of problems down the road.

There is also a known problem with, I believe, less than adequate wire or connector sizing that on some 3 cylinder Yanmars that can cause starting problems, though I thought it was with 3G series. Someone with more direct experience will be along shortly I suppose.
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Old 27-12-2019, 15:27   #7
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Re: 3ym20 Yanmar instrument panel start button won't start

Quote:
Originally Posted by RKsailsolo View Post
Here is description of my issue that happens during start up process....

Press power button. LCD readout displays. Engine check icons light. Buzzer sounds. Press start...everything turns off (buzzer stops and panel power turns off).

New batteries are charged. Oil changed three weeks ago.

Can I replace just the start switch? Or does entire switch panel need replacing?
No and no.
Unlikely to be either of these two components (but possible of course).

More likely to be a corrosion issue in the loom connector between engine and panel or most likely corrosion in the in-line fuse holder in the engine loom. This is usually located IN the loom near the alternator / starter motor.

Supporting reason - The panel power is supplied by the in-line fuse and when power is supplied to the panel, only a very small current flows and panel behaves normally. When the start switch is pressed, a large current needs to flow to engage the start solenoid; this large current is causing a voltage drop at the point of high resistance (i.e. corrosion in loom connector OR the in-line fuse). The large voltage drop causes everything in the panel to turn off.

Note: I am using language the OP should understand, not the language for the electrical experts...


EDIT: After checking the 3YM30 manual, I note Yanmar has moved the fuse form the engine loom to the instrument panel so the above as been altered accordingly , compared to the earlier GM series. I knew I should have looked at the manual first rather than relying on memory
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Old 28-12-2019, 07:47   #8
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Re: 3ym20 Yanmar instrument panel start button won't start

Wotname, many thanks for your thoughtful explanation. Your writing in plain language really hits the objective so less experienced persons can understand and act upon that new insight. I will investigate this new angle today.
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Old 28-12-2019, 09:59   #9
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Re: 3ym20 Yanmar instrument panel start button won't start

Had the same problem on my Ranger Tug, after literally years of checking wire harnesses. starters and on and on turned out to be a start relay on the back of the engine. Relay appeared to work but couldn't click the solenoid. Relay changed, another pesky boat issue solved, My problem only accorded if I did not use the boat for a few weeks otherwise
it would start fine after the first start. Prior to finding the problem I used a remote starter switch (Auto Zone) with a pigtail on the starter solenoid and the other end to a 12 pos on battery - good luck
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Old 28-12-2019, 11:16   #10
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Re: 3ym20 Yanmar instrument panel start button won't start

Could be a bad starter or starter relay. Can you hear the starter relay click? When you hit the button, current is going directly to ground!
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Old 28-12-2019, 11:45   #11
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Re: 3ym20 Yanmar instrument panel start button won't start

Check the high amp side first thusly (a loose or bad connection there can have exactly the same effect as described by Wotname above).

Jump the solenoid from the positive on the solenoid (usually a yellow or yellow with red stripe 12 gauge or so) to the positive supply (i.e. from the battery) connection on the starter.

If the engine turns over briskly, the problem is (the elusive) elsewhere...
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Old 28-12-2019, 11:58   #12
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Re: 3ym20 Yanmar instrument panel start button won't start

Follow up on my input above. Ranger does not have, that any of us owners have found, a wire diagram . I got one off the net, but it was in 2 parts and when it was printed out left out the starter relay. When I metered the solinoid from the starter relay it read 12 v, but would not kick over. The starter relay clicked when the start button was pushed, starter never engaged. Since I had changed the starter, key module, ran new wires I figured WTH and oredred all the relays for the Yanmar. The new starter relay did the trick even though everything metered as working and transferring 12 v. If you stand over the engine facing the transmission the relays are at the rear of the engine near the top, easily reached and changed but not real cheap
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Old 28-12-2019, 15:37   #13
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Re: 3ym20 Yanmar instrument panel start button won't start

On my 3ym30 Yanmar I found the + supply at the rear of the engine to be a loose spade lug, tightened with a crimp & all well now.
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Old 28-12-2019, 20:47   #14
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Re: 3ym20 Yanmar instrument panel start button won't start

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Wotname, many thanks for your thoughtful explanation. Your writing in plain language really hits the objective so less experienced persons can understand and act upon that new insight. I will investigate this new angle today.
After giving your reported fault symptoms more thought and without wishing to sound alarmist, it is possible you have more than one defect.

There could be a minor problem in the +ve supply wire from the engine to the panel (say some minor corrosion) which hasn't caused any observed problem to date. Then a new defect in the start circuit has occurred which is prevents the start solenoid to operate AND exacerbates the earlier minor problem causing the control panel to shut down when you try to start.

Unless you feel comfortable using a voltmeter etc, the only easy solution is to find all the interconnections in the loom between the engine bay and the control panel (usually it is one or two interconnects). Then pull them apart and eyeball them for corrosion, loose terminals and such like.

Most (but not all) defects of this nature will be found to loose/dirty/corroded terminals/connectors.
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Old 29-12-2019, 03:44   #15
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Re: 3ym20 Yanmar instrument panel start button won't start

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Originally Posted by dennismenace111 View Post
Could be a bad starter or starter relay. Can you hear the starter relay click? When you hit the button, current is going directly to ground!
No audible click from starter. Control panel just goes dead.
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