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Old 18-05-2009, 18:33   #1
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Need Ignition Wiring Lesson

Hello,

I have an older Hunter 33 with a Yanmar 2QM20 (original equipment) installed. The engine control panel in the cockpit is in a particularly poor location, situated so that the helmsman is almost certain to step on the key when it is in the ignition switch during rough patches or when wiggling past the wheel to get to the helm station. And this is in fact what has apparently happened frequently over the years, as the key has been repeatedly bent and straightened and now, finally, broken entirely. Yanmar doesn't even make replacement keys anymore and at any rate replacing the key wouldn't address the root problem. So, I have resolved to replace the key ignition with a pushbutton ignition switch, with a safety cover, and with the circuit controlled from below deck (which will prevent any random passerby from firing the boat up and motoring off).

I'm unclear on the wiring setup however. The key switch has three wires to the back, presumably for -12/on/start. A two-pole momentary pushbutton for the ground/start wires will serve to start the thing, but I am unsure how I need to wire it so that the "on" position will work. I have tried connecting the -12/non-start wire, but the panel lights do not come on as I would expect. My thinking is that I would like to put a switch below to turn the ignition "on" and enable the start switch in the cockpit, but I am unsure how to set it up.

I am sure I am badly misunderstanding how all this is supposed to fit together, so I am hoping someone can give me a quick primer on ignition system wiring before I start tearing things apart. Any input appreciated!

Thanks!
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Old 18-05-2009, 22:58   #2
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Just take the wires off the switch and determine the switch logic using a multimeter. Write it down and it should match the diagram in the engine (shop) manual. You now have the diagram for using other switch(es).

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Old 18-05-2009, 23:10   #3
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Scott,

Of course the wiring is not really "ignition" wiring because it is a diesel engine but we know what you mean. You refered to -12v. Isn't the proper power wire +12v? Don't the panel lights light up with +12v applied? Doesn't the starter relay require +12v to entergize?
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Old 19-05-2009, 03:56   #4
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See the Yanmar Wiring Diagram:
http://www.cruisersforum.com/gallery...r&imageuser=79
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Old 19-05-2009, 06:58   #5
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Gord - Looks like that diagram already has a separate key and push button switch.

Scott describes a single off/on/start keyed switch.

Don't know if Scott has the same wiring diagram.
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Old 19-05-2009, 12:05   #6
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Gord- Thanks for the diagram, I will take a look and see if I can figure out what I need. It doesn't match what I had, but it may match what I am trying to get, so that's helpful.

Sorry for the ambiguity regarding voltages; the -12v wire I am referring to is the black wire, or ground, although I didn't want to get into a big terminology debate because it isn't actually "grounded" so I avoided the term. Of the other two wires, I get a +12v reading on one of them (red) and it clearly belongs to the start circuit since when I cross it with the -12v the starter fires. This does NOT however cause the panel to light up (nor should it, since that circuit should only be completed when the starter is turning).

The third wire is striped red and black, and no combination of crossing it with the other two will light the panel up. I get a 12v circuit with a multimeter measuring between the -12v and +12v wires (as you would expect) but no reading at all between the third wire and either of the other two. Thus my confusion.

Hopefully Gord's diagram will help me puzzle it out but if anything else in this post has made the answer blindingly obvious to someone, feel free to shout it out!

Thanks!
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Old 19-05-2009, 21:33   #7
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Scott,

You are using your meter to test the wires. Like I wrote before, use it on the switch instead. Disconnect the three wires, switch the meter to resistance/ohms and test the switch for the 3 different key positions. That will learn you exactly which wire is switched to which other wire. Consider the switch a "black box" with three terminals and find out what happens inside when turning the key.

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Old 20-05-2009, 07:47   #8
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Ah, I see what you are saying now. That makes sense... unfortunately, the reason I am going through all this now is that the original switch is broken, so I'm not going to be able to get any reliable readings out if it at all.

I went over the wiring diagram last night that Gord posted and while it's not a one-to-one match with my engine wiring harness, it has at least given me some ideas of what to try next. I'll give it a shot this weekend and report back.
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Old 20-05-2009, 09:58   #9
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Connect the meter (or test light) black to ground. Test the wires at the back of the switch, one should be hot. This is your incoming power.Turn the switch to position one (before the starter motor energizes) find which of the remaining two wires is hot. This wire will need a toggle switch to power up the gauges, lights etc. The remaining wire should go to your new push button switch. If your engine is keyed shut down (in lieu of a pull cable) you should put the toggle switch on your engine panel.
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