Voltage Drop to coil

[Jrain 276]

Hello just a real quick intro , I have been a big fan of  W/H tractors I saved  a 90s 212-5  that I picked up in my friends scrap yard 15 years ago got her up and running and she has been mowing my 3/4 acre lawn for all those years with out a hitch of course I take care of her , So I just recently retired and so now I have time to do all my property up keep , and part of the up keep would be grooming my gravel driveway and road about 1200 feet , So I stopped by my friend who is a scraper and  picked out a 1974 C120  it looks like it could do the job of keeping my gravel road and drive way groomed ,  Now here is where I need help , I went through the tractor  replaced lines, filter, shut off  new carb    and cleaned fuel system , on the electrical side  new switch , new battery , new solonoid , new condenser , new ing coil , new spark plug coil wire , new spark plug and new points , and replaced wires that were dry rotted .  So now I have engine good positive engine cranking in cranking position on key switch , when I turn the key to first position (on Position )  I get 12 volts to the ing coil  but as soon as I go to crank position (engine cranking ) the 12 volts to the coil drops leaving No ing spark to plug and points ,but  If I run a wire straight from the battery to the ing coil  the engine fires off and runs with no issues as long as I keep that temporary wire attached from the battery to the ing coil.  The voltage drop occurs at the switch , the switch has 2 poles that have 12 volts when keyed in the on position but both drop out when keyed to crank position . I do not get it and its driving me crazy ,do I have the correct switch did I miss something in the wiring of the switch , I have looked at wheel horse wiring specific diagram for the C120 and others and they all seem to be wired the same way.

[gwest_ca-(File Mod) 11,046]

 

[Ed Kennell 38,227]

to the   Sounds like you have a faulty switch.

[roadapples 6,983]

[Jrain 276]

So you guys think Bad switch , Ok , So I bought this one at tractor supply . So can you recommend  On a switch brand  , type and where to get one 

[Ed Kennell 38,227]

I would return that switch to TSC and check a new one with your VOM to see if it drops the continuity from battery to coil terminals when in the start position.  My TSC employees are very helpful and they should replace the switch if you show the fault.

[lynnmor 7,308]

You likely bought the wrong switch, there are an number of ignition switches that look almost the same.  Compare the new and old, especially the letters next to the terminals.

[Jrain 276]

There was no switch in the tractor so really do not know what the number is and where to get one if that is the issue ,guess will have to order one from a  WH dealer

[gwest_ca-(File Mod) 11,046]

The aftermarket industry is familiar with the battery type 103990 ignition switch because it is so popular. The I (eye) terminal powers the ignition.

You may have got a magneto type 103991 switch and it is guaranteed not to work. The M terminal controls the ignition.

Have a Napa you can try? Even a local lawn mower repair shop likely have one.

 

Garry

[Crazyredhorse 295]

have you tried new ignition wire from switch? check that first other than that it would have to be switch. bad ground? unless lights wire or somthing like that draining it. or you have ign wire wired to a lights position on switch?

Edited June 7, 2021 by Crazyredhorse

[Handy Don 12,235]

I agree the switch might be defective, but I'd check it before taking it back using the document that @gwest_ca added, paying attention to the diagram that shows which terminals are connected to each other at the different position. 

If the battery is connected to "B", then:

- there should be juice at the "I" , "R", and "S" terminals of the switch when the key is in the start position

- there should be juice at the "I", "R", and "A" terminals of the switch when the key is in the run position

 

It may be that you have the connections to A and R swapped.

 

Good luck and welcome!

 

Edited June 7, 2021 by Handy Don

[953 nut 55,316]

Your Ignition coil needs to be internally resisted or it will shorten the life of your ignition points significantly.  The drawing below uses the 103-990 switch and shows what components interact with each-other.

[Jrain 276]

You guys are great thank you for all the input . I do believe that I did purchase the incorrect switch , So I ordered the correct switch that has  S B R I A  terminals Part #  103990, 111216 Lesco 050102 , Handy Don you are correct I had bought from Tractor Supply the M type switch , I had no prior knowledge there where so many different types for tractor key switches . 953 Nut  that is the diagram I used and also found PDF manual for 1974 wheel Horse C120 witch is same model and year this tractor is  to compare wiring diagrams . I will admit I am not a tractor guy and will be looking and asking here a lot . I should have the new switch in a couple of days ,I will report back and let you know . Again Big thank to all.

[Crazyredhorse 295]

also wonder if it could be a safety switch going or bad and you bypass it when you hook it to battery direct.i guess it would t even turn over if that were the case

Edited June 8, 2021 by Crazyredhorse

[Handy Don 12,235]

You're welcome.

When you think about Wheel Horse's being designed and manufactured for over 50 years, and in a range of sizes and capabilities, it becomes easy to understand why things can be a bit complicated at times.

We here are happy when tractors are working for their owners. There are times, though, when we are happy to just sit and admire them--our own and others'. And to do that, we like to see PICTURES!!

 

[Jrain 276]

10 hours ago, Crazyredhorse said:

also wonder if it could be a safety switch going or bad and you bypass it when you hook it to battery direct.i guess it would t even turn over if that were the case

The fist thing I always do  is go through the entire wiring harness and electrical components all wires were checked for resistance ,wires that were cracked (dry rotted ) were replaced eyelet  connections that were bad were replaced all switches were checked for function cleaned and sprayed with Deoxt witch is a amazing electrical cleaner lubricant witch is really for restoring old linear pots and audio taper pots but all so works wonders for old switches  ,grounds were all replaced and cleaned , as I said all Ing. and starting electrical components were replaced with new ones . when it comes to electrical I buy everything new and replace I have learned over the years when in series electrical components fail it just at matter of time before the next component fails ,I guess you might say I am a firm believer in preventative maintenance or you might say I have OCD , but thank you for your input on my electrical dilemma its nice to know you guys are here to help others . 

[Jrain 276]

11 hours ago, Handy Don said:

You're welcome.

When you think about Wheel Horse's being designed and manufactured for over 50 years, and in a range of sizes and capabilities, it becomes easy to understand why things can be a bit complicated at times.

We here are happy when tractors are working for their owners. There are times, though, when we are happy to just sit and admire them--our own and others'. And to do that, we like to see PICTURES!!

 

OK I will get some pictures up so you can take a peek , I see you guys have a big passion for wheels horse tractors and you have me thinking maybe I should go back to my friend place and grab what I think is a M80 before he cuts it up besides have to go back anyway I saw lots of wheel weights maybe I can find something that will fit the c120  and see what other attachment he has I know I saw a good amount of red mower decks laying around so I might find something I need for the c120.

[953 nut 55,316]

11 hours ago, Jrain said:

I am not a tractor guy and will be looking and asking here a lot .

Please feel free to ask any questions before hand. We are here to help and once you have asked enough questions you will become a tractor guy.

[Jrain 276]

So ok got the new Key switch yesterday ,So I was able to get to the C120 today and She fired rite up and runs like a top , let her idle and warm up ,then shut her down to do a oil change and get the air cleaner back on with a new air filter ,checked the hydro , tranny fluid ? ok did not expect to see that but it was like it was just put in , nice clean looking and good smelling transmission fluid , aired up the tires and took if for a good 20 minute ride ,at different throttle positions, up and around my gravel roads ,did not even miss a beat up my steep hill , drove back home and did another oil change just to be on the safe side , then I decided to give the mower deck a once over to see if I could get her spinning  got the lube gun out and greased every fitting I could find ,then turning by hand all till everything on the deck felt free , made a adjustment to the PTO engagement arm and and eased it in and out a few time till I felt everything was running smooth . got my deck height adjusted and  mowed the grass ,even though I do not plan on using it as a mower , this thing is a beast holy-cow my 212-5  with a 38 inch deck has nothing on this deck ,I believe it somewhere about 50 inches . I also was able to stop by my friends place and pick-up a few more things for the c120, I got a pair of wheel weights that fit the rim pretty good and they are  50 to 60 lbs each ,I also picked up some hydraulic stuff  with a pully driven pump that I think I can work with .  I saw a real nice WH mower deck has to be at least 42 inches and it is in excellent condition . told him not to cut it up , I will come back for it. So again a big thanks for all the help .