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ScottR

Electrical changes for M12 to M14 swap

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ScottR

I saw some discussion on swapping an M12 for a M14 over in Engines.  I have a 1995 M12 that I'm considering swapping with a 1989 M14. The boys in Engines felt it was a plug and play operation but weren't sure about the electrical aspect.  Does anyone know whether the M14 will just connect right up electrically or would I have to do some mods?  I don't have the M14 in my possession to compare them.

 

I appreciate any advice.

 

Scott

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Save Old Iron

The wiring connector near the engine supports 5 wires

 

 

 

 

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If the orientation of the new engine's connector matches the existing harness orientation, all is well. It should be the same.

Edited by Save Old Iron
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ScottR

This is very helpful. Thank you.

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ScottR

The M14 connector has five wires going to the engine, the M12 only has 4. I've scratched my head over the wiring idagrams but am puzzled as to what I would do to the M14 connection to make it work without changing anything on the other half of the connector.  The M14 is out of 1987 414-8.  The M12 is from a 1995 312-8.

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gwest_ca

The wiring diagrams in the operator manuals are drawn similar to each other so easier to compare.

 

1987 414-8

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1995 312-8

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Which tractor is getting which motor?

 

Garry

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ScottR

The 312-8 is getting the M14. Thank you for the manuals. Both of your attachments are for the 312-8, but I have the 414-8 wiring diagram. Still scratching my head though since the diagrams don't show the connector. 

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gwest_ca

Sorry about the wrong link. Fixed now.

 

There looks to be extra wires in the diagrams but if you follow them they are joined to another at the engine in the diagram. They likely are not connected together on the engine side of the connector.

 

The dark green wire on the M14 is the AC output from the stator and it goes to the lights only. You need to disconnect the feed to your headlamp switch and connect it to that green lead. The lights will work only when the M14 runs.

 

I think the rest of the wires function the same except there are color changes.

The light blue and dark blue on the M14 low oil switch go to the orange and tan on the 312-8. If you get this circuit wrong the starter won't work.

 

The white wire with the diode in it from the M14 charging stator goes to the white wire in the connector. The M14 does not use a voltage regulator. 

 

There is a dark blue wire from the M14 magneto. Make sure you have identified it. It must go to the pto switch and on to the ignition switch. This wire simply grounds the ignition to stop the engine. Do not allow any battery power into that wire. Since there is more than one dark blue wire leave this one disconnected for now. The engine should run. To shut the engine off ground that wire to the chassis or battery negative terminal. This way if you pick the wrong dark blue wire on the 312-8 no harm done. If everything works as planned hook up the blue magneto wire.

 

Garry

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ScottR

This helps a lot. Thank you Garry.

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