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Discussion Starter · #1 ·
Hi my name is Andrew,
1st thanks to all. I've been reading this forum for many months now and have really learned a bunch about my 1st 1967 JD 112.
My problem: This is my very 1st lawn tractor. Its a JD 1967 112. However the engine is a tecumseh HH120 that im suspecting came out of a sears suburban rig.
The tractor is wired as a 1967 112 but I have a solid state ignition with no stator, just the coil under the fly wheel and silver triangle ignition unit above it.
I've re-wired everything, the new ignition switch is a 3 pronged B, S, and I. On the ignition side of things the coil has 2 black wires from behind the flywheel 1 to the triangle unit the other I do not know where it goes?? I do know if i attach it to the sheet metal i get no spark, I can also kill the engine by touching it to the sheetmetal. If I leave it un attached the tractor runs like a champ; and fires right up. FINNALLY THE PROBLEM I cannot turn off the tractor using the key. Attached is a photo of a similar engine the way mine is set up. Refer to the picture red spots. If I wire it like this, no spark. If I remove the wire on the left attached to the tin metal; she roars right up. Im thinking maybe I have the wrong ignition switch? The 2nd black wire need to attached to?? I really don't want to blow up the ignition unit doing trial and error... Thx!!

Motor vehicle Gas Machine Auto part Nut
 

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Welcome! We like pictures of tractors around here.
 

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Andrew,
Welcome to WFM! I have a '67 112 with Tecumseh which is stock. I can get a shot or wiring diagram from service manual that will help you. I'm not an electrical guru by any means so maybe someone else can help you in meantime.
 

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Discussion Starter · #4 ·
Hi my name is Andrew,
1st thanks to all. I've been reading this forum for many months now and have really learned a bunch about my 1st 1967 JD 112.
My problem: This is my very 1st lawn tractor. Its a JD 1967 112. However the engine is a tecumseh HH120 that im suspecting came out of a sears suburban rig.
The tractor is wired as a 1967 112 but I have a solid state ignition with no stator, just the coil under the fly wheel and silver triangle ignition unit above it.
I've re-wired everything, the new ignition switch is a 3 pronged B, S, and I. On the ignition side of things the coil has 2 black wires from behind the flywheel 1 to the triangle unit the other I do not know where it goes?? I do know if i attach it to the sheet metal i get no spark, I can also kill the engine by touching it to the sheetmetal. If I leave it un attached the tractor runs like a champ; and fires right up. FINNALLY THE PROBLEM I cannot turn off the tractor using the key. Attached is a photo of a similar engine the way mine is set up. Refer to the picture red spots. If I wire it like this, no spark. If I remove the wire on the left attached to the tin metal; she roars right up. Im thinking maybe I have the wrong ignition switch? The 2nd black wire need to attached to?? I really don't want to blow up the ignition unit doing trial and error... Thx!!

View attachment 287207
Andrew,
Welcome to WFM! I have a '67 112 with Tecumseh which is stock. I can get a shot or wiring diagram from service manual that will help you. I'm not an electrical guru by any means so maybe someone else can help you in meantime.
thank you. That would help much appreciate it
 

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Your thought that the key switch in your tractor needs to be changed is correct, Don't use it as is! It is probably the correct one for the 10HP Tecumseh that had a battery/coil ignition, and a starter/generator/ regulator type charging system originally in the tractor . Not good for a Solid State ignition.
The I terminal on that switch should have 12V when the key is in start and run positions. The wire you refer to that will kill the spark, when grounded, needs to be connected to a switch that grounds it to the frame but is open (not grounded) when the switch is in the start and run positions. If it is connected to 12V it will fry the solid state unit, just as you suspect.
Questions, is the pic above of the tractor you have? With a starter/generator? Does it have a regulator in the system as in the original 112 RF would use?

Now what to do? A good key switch for a '68 112 ( and maybe '69-'70) that had a 10HP Tecumseh with Solid State Ignition could be utilized. ($80 at HAPCO) Properly wiring it to match the charging system may not be plug and play, though. I would think you would want a wiring diagram for the RF 112 plus the '68 112 to compare.
Maybe you would want to add a relay the the "kill wire" and use the switch now in the machine to engage it. I will let someone well versed in that mod school you in doing that and what to get. Many of the repowers use this method and it works well.
Or use a grounding push button switch on the dash that is grounded to the frame.
Good luck!

tommyhawk
 

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Discussion Starter · #7 ·
Hi Tommyhawk,
I think you hit the nail on the head! After tossing and turning all nite rewiring the thing in my head, i came to the same conclusion....
Your correct, the tractor is wired perfectly for a 1967 JD 112 with coil and points. However correct again, my Tecumseh 120 and ignition does not match.
I'm actually on vacation so this morning I did some cross referencing between the JD parts catalog for the years the 112 had the solid state ignition. I came up with switch AM 31995 5 pronged bronze.
I purchased one through Zoro, a Stens switch that have the markings A, M, B, R, and S. My 3 pronged switch only has S, I, and B. I just now have to figure out and transpose where the wires go in particular im thinking the coil grounding kill wire to M? Ill have to check with my meter after it arrives and see what prongs have and have not voltage in the different 3 positions.
Thx Andrew
 

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Discussion Starter · #8 ·
Your thought that the key switch in your tractor needs to be changed is correct, Don't use it as is! It is probably the correct one for the 10HP Tecumseh that had a battery/coil ignition, and a starter/generator/ regulator type charging system originally in the tractor . Not good for a Solid State ignition.
The I terminal on that switch should have 12V when the key is in start and run positions. The wire you refer to that will kill the spark, when grounded, needs to be connected to a switch that grounds it to the frame but is open (not grounded) when the switch is in the start and run positions. If it is connected to 12V it will fry the solid state unit, just as you suspect.
Questions, is the pic above of the tractor you have? With a starter/generator? Does it have a regulator in the system as in the original 112 RF would use?

Now what to do? A good key switch for a '68 112 ( and maybe '69-'70) that had a 10HP Tecumseh with Solid State Ignition could be utilized. ($80 at HAPCO) Properly wiring it to match the charging system may not be plug and play, though. I would think you would want a wiring diagram for the RF 112 plus the '68 112 to compare.
Maybe you would want to add a relay the the "kill wire" and use the switch now in the machine to engage it. I will let someone well versed in that mod school you in doing that and what to get. Many of the repowers use this method and it works well.
Or use a grounding push button switch on the dash that is grounded to the frame.
Good luck!

tommyhawk

I forgot to answer your question, Yessir that's my 112 with Starter/Generator combo.
 

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Yes, I think you will find "M" goes to the "kill wire". I'm pretty sure the switch body must be grounded to the pedestal, which must have a good ground to the frame and engine.
"R" to the regulator.
"A" to accessories, cigar lighter, circuit breaker, headlight switch.
"B" battery to/from ammeter, hot side of solenoid.
"S" to neutral safety switches to small post on the solenoid.

Thankfully you have, and know how to use the VOM. I'm looking at a later wiring diagram for a 112 with a starter and stator/regulator/rectifier. The regulator used with the starter generator on a RF is different of course, all DC. What lug is used on it must be determined with a RF wiring diagram. Hopefully you will be able to obtain copies of both. I just found out my scanner doesn't work, again, or I would post what I have for you.
Hang in there, you will get it!

tommyhawk
 

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Discussion Starter · #10 ·
Hey Tommyhawk,
I'm using these 2... Top is the 112 serials 130,000 to 160,000 the SSI models and the bottom 112 serials 15,000 to ?? my serial number is 017086M

Wheel Tire Vehicle Automotive tire Motor vehicle


Here is another picture of mine. It wasn't in bad shape at all.... it just needed some TLC and elbow grease and of course a new ignition switch! LOL.


Schematic Font Parallel Rectangle Diagram

Rectangle Slope Font Schematic Parallel
 

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That should do it. That is a nice looking tractor.
My '68 112 is s/n 108xxx but more closely matches the wiring diagram for 130000-160000. When I restored it, I bought a used, but nearly new wiring harness that was probably for the newer s/n's. Had no problems with it though. Mostly color changes to the wi Lucky to find that one as new ones were NLA from JD before 2003.
I was able to get a new one for the '67 110 from JD in 2009. Probably NLA now too.
 

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Discussion Starter · #12 ·
Well, thank you for all your help and suggestions. I appreciate all the help everyone gives each other on this site and in general the comaradirie. I’ve always wanted a round fender now that I have one, I now know why this is a great forum especially to us novices!
 

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Discussion Starter · #13 ·
Happy New Year!
Tommyhawk; just a follow up. I hope this helps others with mixed tractors with solid state ignitions.
I received the new john deere switch AM 31995 and finally made it out to the garage today. I left the old regulator in place and wired the kill wire (white) from the coil lead under the flywheel to the M terminal on the new ignition switch. The purple wire from the solenoid to the S terminal, the red wire from the voltage regulator to the B terminal and the orange wire to the A terminal.
She starts right up, more importantly I can turn her off at the ignition switch to off.
Thx Again
 
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