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Mf12 Ignition Switch


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#1 cheluIS OFFLINE  

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Posted February 13, 2014 - 05:06 PM

I want to change the ignition switch and I'm in standstill.

I have this original switch :

S1.jpg S2.jpg

And as I can see in wiring diagram I have these wires :

wiring diagram.jpg

B=Battery - green

C=Charge ? - black

S=Starter ? - white (yellow)

D= ??? - Pink (red)

 

My new switch has 3 position :

OFF

ACC(accesories)

S(starter)

The new switch has 3 terminals :

1 common with +Vcc

2 acc

3 starter

I cannot figure out how to connect the wires .As I read in several topics in this forum to stop engine you must apply ground to a wire - which one ?? and don't apply +Vcc to which wire ?

If anybody can explain how original switch works and how to convert to new switch ?

 

Thank you very much .

 



#2 MH81 ONLINE  

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Posted February 13, 2014 - 05:09 PM

I don't think the new switch is correct. The wire that goes to the spark unit (CDI ) should NEVER EVER have power on it.

#3 cheluIS OFFLINE  

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Posted February 13, 2014 - 05:26 PM

Which wire goes to CDI (what colour) and what potential apply - ground ?

#4 MH81 ONLINE  

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Posted February 13, 2014 - 06:23 PM

I should ask, is this engine a magneto (points under little cover on pulley side of engine) or CDI (no points)

Converting a new switch over to an old style system is not easy in my opinion. It requires a relay to change the power to ignition to a ground to kill spark. You should find the right switch, would be much simpler. Another option is to carefully open the old one and clean it.

The old switch worked this way: the power was applied to the switch for the activating the starter circuit and to allow the charging to work properly. In the schematic above and on Ryan's tractor, the lights could be turned on without the key, so they have no bearing.

The second half of the switch was a shorting of the spark kill wire to ground. The contact was shorted from the " kill" terminal to the body of the switch, which was mounted in a grounded panel.

I believe you have the right designations for the wires you have listed and the red/pink wire should be the one that goes to spark kill. It will run from the switch to a small insulated board on the flywheel side of the engine (towards the front). From there the wire will either go under the tin and behind the flywheel or across to the points.

Just be very, very careful on the hookup. A mistake here can cost lots of money to correct.
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#5 cheluIS OFFLINE  

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Posted February 14, 2014 - 02:37 AM

@MH81 Thank you for info . I was thinking to put a relay too . I first have to understand very well how this switch works and then find a solution to modify .

At the end I must find a solution .

My original switch is mechanical demaged , cannot fix it . And here in Romania is very hard to find parts for MF , so I have to make adaptation .

Any other sugestions are welcomed .



#6 KennyP ONLINE  

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Posted February 14, 2014 - 08:31 AM

Anybody have a spare switch to send over there?


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#7 cheluIS OFFLINE  

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Posted February 14, 2014 - 01:52 PM

The original socket :

S.jpg

 

After few hours I came out with this .

New switch.jpg

 

Please study and tell me your opinions .

It should work .

The relays are for automotive and  30 Amps.


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#8 MH81 ONLINE  

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Posted February 14, 2014 - 03:42 PM

The second relay, why is the ACC running to it. I see that the starter circuit is activating it, but do not see the need for the ACC to be switched on it. I think you could just use the s to power your starter solenoid. The big thing is that the power never reaches the CDI and it can ground out when the key is turned off.

EDIT: Oh I see. It has something to do with the charging.

Let me study this some, but my impulse is to say one double pole, single throw controlled by the ACC and the S just powering a solenoid is the easiest.
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#9 cheluIS OFFLINE  

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Posted February 14, 2014 - 03:59 PM

I need two relays becouse the second is working only when starter is on and is separating the charging circuit.The first relay is on when the engine is running . I don't see how to use a single relay with a double pole .
My single concerne is when starter is on the current is big and it might cut off the power to relays and give ground to kill wire .
Tomorrow I'll do the circuit and do the test.
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#10 MH81 ONLINE  

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Posted February 14, 2014 - 05:43 PM

OK, so the second relay just breaks the charge circuit when the starter I engaged? I think the coil latching on the relays should be ok with a good battery. Relays normally they have a voltage at which they unlatch. Does yours specify that?

#11 cheluIS OFFLINE  

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Posted February 14, 2014 - 06:52 PM

Yes the second relay brakes the charging circuit when starter is engaging .I mesured the original switch and when in start position the Charge is disengaged.
I think the unlatching voltage is 6.9 V

#12 MH81 ONLINE  

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Posted February 14, 2014 - 07:26 PM

It would take a very cold day with a mediocre battery to cause it to drop all the way down to 7.

A third option might be to put a separate kill switch in. Something separate and just for shorting out the CDI wire.
You would have to turn off the key switch and the toggle to shut down, but it would eliminate one relay and any possibility of power to the CDI.

#13 DH1 OFFLINE  

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Posted February 14, 2014 - 08:54 PM

Why not just use a DPDT switch, and a push button switch.

 

-connect one side of the switch to to ground out the ignition.

-connect the other side of the switch to connect the battery to the regulator output.

-use the push button switch to turn on the starting motor.


Edited by DH1, February 14, 2014 - 08:57 PM.


#14 cheluIS OFFLINE  

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Posted February 18, 2014 - 04:14 PM

Made the circuit for original ignition switch replacement .

 

S01.jpg S02.jpg S03.jpg

S04.jpg S05.jpg S06.jpg

 

I put the two relays on a metal band and I grounded it.

 

Made the connections with the tractor's wires.

 

S07.jpg S08.jpg

 

And YES , it works !!! :rocker2: :rocker2: :rocker2:

 

Of course , the proof :http://youtu.be/n8158QErcQI


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#15 MH81 ONLINE  

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Posted February 18, 2014 - 05:01 PM

Adapt, overcome, persevere. :thumbs:




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