Onan swap wiring

[jamesdart 3]

I had this really good running onan p216 and a 312-8 that wasn’t working for me power wise.

 

i put the onan in the 312, not done yet.  Looking for some

help with the wiring. I don’t know what years either are, 

the onan I think was from a wheelhorse, it has the toro sticker. 
it was in a Massey parts tractor I bought. 
it had the 5 pin plug like the wheelhorse in the harness but I know they use a different ignition kill.

I put power to the coil and jump the engine at the starter it runs and charges but I need to get this thing wired up properly.
where do I get the ignition and start + from? 
I would like to retain the Saftey switches in case my wife or son use it. 

do the coil+  and start wires normally go through the Saftey switches? Or only the start wire? 
 

Edited October 26 by jamesdart

[gwest_ca-(File Mod) 11,071]

What type of ignition do you have?

You say it starts and runs - is that without doing anything for the ignition? This suggests magneto ignition with kill circuit.

The coil+ suggests you have battery ignition.

[953 nut 55,394]

23 hours ago, jamesdart said:

put power to the coil and jump the engine at the starter it runs and charges

I presume the 312-8 was powered by a Magnum engine and the Onan has a 12 volt ignition coil based on this statement. If that is true The safety switch arrangement on the 312-8 will need to be altered along with the ignition system.

Please confirm the ignition system types before we dive too deep into this. Once we know for sure I will help walk you through the transition.

Below is a bit of information I put together to help people understand safety switches.

Knowing the model number of the 312-8 will be very helpful.

Frequently we field questions about safety switches and many times the answers given may or may not be correct for the particular Wheel Horse we are talking about. For accurate information it is best to refer to the “Demystification Guide” or electrical drawings for the specific model and year tractor. There is no one size fits all answer, I will attempt to provide a little food for thought and some general information on the subject.

First, we need to understand how various switches receive their names. The switches used in safety systems are momentary switches, if no force is applied to them, they return to their “Normal” position. That would be the same condition (open or closed) that they had when they were on the shelf ready to be installed. Some will be NO (normally open) and some will be NC (normally closed). In the case of PTO switches there are two switches ganged together.

The seat switch and half of the PTO switch are used in the ignition circuit. The second half of the PTO switch is in the starter circuit.

As an example, the Seat and PTO safety switches for a Magneto or Trigger Ignition system are designed to ground out the magneto if the PTO is engaged and there is no driver in the seat. These switches are in series. The seat switch is a N.C. (normally closed) switch which opens when weight is placed on the seat. The half of the PTO switch that is in the ignition circuit is N.O. (normally open) which is open when disengaged and will close when engaged. With the PTO switch closed and no weight in the seat the magneto will be grounded and the engine will stop running. With the PTO disengaged the seat switch will have no effect.

If the tractor has a Battery Ignition system the PTO and Seat safety switches are wired to interrupt the power from the ignition switch to the ignition coil when the PTO is engaged and there is no driver in the seat. These switches are in parallel. The seat switch is a N.O. (normally open) switch and will close when weight is on the seat. The half of the PTO switch that is used for ignition is N.C. (normally closed) and opens when the PTO is engaged. Both of these switches receive power from the ignition switch “I” terminal and either one being closed will pass the power on to the ignition coil. If the PTO is engaged that switch will open, as long as there is weight in the seat the engine will continue to run because the Seat switch will be closed. If the weight is removed from the seat while the PTO is engaged the engine will stop. If the PTO is disengaged the seat switch has no effect.

Looking at the drawings below should clarify this muddy issue.

 

Edited October 27 by 953 nut

[953 nut 55,394]

@jamesdart,  without knowing the model number of your 312-8 we can't give you the help you are seeking with any degree of accuracy. The 312-8 was produced from 1985 until 2001 and went through several wiring system changes over the years.

The model number will be found on a decal under the seat. 

Model numbers for 1985 to 1992 would consist of one or two numbers followed by 12K80_ and an additional number. For example, 21-12K801 would be a 1986.

From 1993 to 2001 the model number became a five digit number. 73_ _ _. For example the model number for a 1996 321-8 would be 73363.

[jamesdart 3]

2112k805

i got the starter working from key and clutch switch. 

[953 nut 55,394]

19 hours ago, jamesdart said:

2112k805

i got the starter working from key and clutch switch. 

Everything in the starter wiring is compatible including the safety switches.

Your 312 is a 1988 and can be modified to operate with a battery ignition system by adding a couple of five pin relays.

The safety switches and key switch on a magneto ignition system will turn off the ignition by grounding it. We can add relays with power going to the coil that activates the relay and the safety switches or ignition switches will provide a ground to the other end of the coil to activate it.

This may sound complicated but it is a whole lot easier than rewiring the tractor and will only cost about $ 10.00.

The 1987 to 1991 Wheel Horse use the 103-991 ignition switch which complicated things just a bit but I have it figured out.  

 

I will be working on drawings to get this done.

 

 https://www.ebay.com/itm/145799344059?chn=ps&norover=1&mkevt=1&mkrid=711-166974-028196-7&mkcid=2&mkscid=101&itemid=145799344059&targetid=2200106847495&device=c&mktype=pla_with_promotion&googleloc=9010285&poi=&campaignid=19855151517&mkgroupid=164992719498&rlsatarget=pla-2200106847495&abcId=9307298&merchantid=603860452&geoid=9010285&gad_source=1&gclid=Cj0KCQjwm5e5BhCWARIsANwm06iDR96RAp-7cVsG9Y5CyYPnMGPJmkQrpFd4KIc2r51Sluj3j7-gjboaAnahEALw_wcB

 

 

Edited November 3 by 953 nut

[953 nut 55,394]

I have reviewer my drawings and feel confident that this will work. The engine will shut off whenever the operator leaves the seat regardless of the PTO switch position. This is a bit inconvenient but it is the only way I could find without rewiring the safety switches. The wire gauge used on the safety switches of a magneto ignition tractor are too small to be used for a battery powered safety switch system.

Since the Ignition switch does not have power to the "A" accessory terminal in the Start position we will use one relay to provide 12 volts to the ignition coil during Start. This will be done by running a wire from the small purple wire on the solenoid to the relay terminals 30 and 85 to finish 12 volts coming from terminal 87 of the start relay to the ignition coil + when the relay closes.

The Dark Blue wire from the PTO switch that presently goes to the magneto coil will be disconnected from the magneto and eliminated. A wire from the seat switch light green side will be connected to relay terminal 86 to allow the relay to close if the operator is in seat during Start.  See start diagram

 

When the key is released to the Run position the second relay will provide 12 volts to the ignition coil. The white wire from the voltage regulator to the ignition switch will be spliced into and connected to relay terminals 30 and 85. The ignition coil and light green seat switch wires will be the same as the other relay.   See run diagram and combined diagrams.

[jamesdart 3]

Thank you sir. I’ll let you know how it goes