What is the Sequence of safety switches in order to start

[Pat Marchwick 88]

Trying to figure out the sequence of the electrical current going thru the safety switches fron key switch to the starter-engagement.

I am not the best at reading electrical schematics so please help me out .

if I put my idiot  light clamped to the ground of the battery when I put my test probe on the

#1 in sequence?, the PTO safety switch I should have power going in  and if the pto disengaged going out to

#2 in sequence?. The parking brake switch, if brake is on power should be sent to next switch

#3 in sequence?, the seat switch, if seat switch is depressed power should go to the next switch

#4in sequence?, neutral safety switch, if transmission is in neutral power should go to the next switch

#5 in sequence?, low oil switch, if above allowed low level power should go to the next switch

#6 in sequence?, air filter restricted switch, if air filter is clean power should go to the next switch

now if all switches are proper it is ok to send power to solenoid to start the machine

 

please help me in confirming the proper sequence so it is easier to track and find the problem switch.

thank you

this should help myself and a lot of other shade tree mechanics!

 

Model # 4120oe02
SERIAL # 1031323

1991 pretty sure?

 

 

Edited February 15 by Pat Marchwick
Model and serial added

[JCM 9,168]

The man to talk to would be @953 nut  or @gwest_ca. Only thing I could help with is the air cleaner switch is not part of the electrical wiring sequence on a 520.

[gwest_ca-(File Mod) 11,045]

What is the model number and serial number of the tractor? Many changes in the way it was done over the years.

[Pat Marchwick 88]

I will get that tomorrow.

but is there a sequence of switch activation to get the ok to activate the solenoid?

[oliver2-44 9,753]

How they are wired establishes the sequence. So if the tractor is wired like the wiring diagram then that is the sequence. Some may be wired in parallel. 

[squonk 41,118]

I would think the seat switch would be first in line. If you're not sitting on the tractor, the others won't matter. 

[953 nut 55,237]

10 hours ago, Pat Marchwick said:

if I put my idiot  light clamped to the ground of the battery when I put my test probe on the

 

9 minutes ago, squonk said:

I would think the seat switch would be first in line. If you're not sitting on the tractor, the others won't matter. 

It all depends on the model, safety switches for start position on the older models didn't have much more than a clutch switch and half of the PTO switch. Newer models have no electrical power going to the safety switches, they provide a ground for the coil of a relay that passses voltage to the solenoid.

We need the model number to give a correct answer.

 

[Racinbob 11,081]

11 hours ago, Pat Marchwick said:

Trying to figure out the sequence of the electrical current going thru the safety switches fron key switch to the starter-engagement.

I am not the best at reading electrical schematics so please help me out .

if I put my idiot  light clamped to the ground of the battery when I put my test probe on the

#1 in sequence?, the PTO safety switch I should have power going in  and if the pto disengaged going out to

#2 in sequence?. The parking brake switch, if brake is on power should be sent to next switch

#3 in sequence?, the seat switch, if seat switch is depressed power should go to the next switch

#4in sequence?, neutral safety switch, if transmission is in neutral power should go to the next switch

#5 in sequence?, low oil switch, if above allowed low level power should go to the next switch

#6 in sequence?, air filter restricted switch, if air filter is clean power should go to the next switch

now if all switches are proper it is ok to send power to solenoid to start the machine

 

please help me in confirming the proper sequence so it is easier to track and find the problem switch.

thank you

this should help myself and a lot of other shade tree mechanics!

 

 

 

 

That write up hinted of a PLC controller 

 

I very rarely get into electrical issues via computer or even phone. Far too many potential (pun) issues can crop up for so many reasons I find it best to just stay away if I can't see it in person. The guys here are trying to help but even with good intentions things can get even more confused. It's absolutely imperative that they know the exact tractor you have. I'm going to say that you have a 520H but what year? If you don't know then post the model # and we'll tell you. Even knowing that and having the schematic in front of me I would only say what it SHOULD be. Without seeing it I can't be certain what it actually IS. Rewires and other changes usually come into play on these older machines. Oh, there was some bad wiring so I replaced it with.........the identifying color of the insulation could mean nothing cuz electricity is color blind. The there's always the "well you said to do this" when really it was "I thought you meant to do this".

With that being said Pat, post all the info on your tractor and the guys will get the proper diagram. That should minimize the possibility of errant information. 

Edited February 14 by Racinbob

[lynnmor 7,306]

Use the Demystification Guide to see each system on your tractor.

[Handy Don 12,232]

41 minutes ago, lynnmor said:

Use the Demystification Guide to see each system on your tractor.

The guide is the best way I’ve found to wrap my head around the different ways the WH engineers designed these systems. With each set of components, regulations, and market forces they had to adjust their approach.

And @Racinbob’s observations are absolutely valid--“it may well have been altered somewhere along the way.” Heck, I’m as guilty as any PO since I’ve replaced damaged wiring without sticking to “original” colors and I’ve upgraded a non-solenoid system to solenoid..

 

[Racinbob 11,081]

53 minutes ago, Handy Don said:

The guide is the best way I’ve found to wrap my head around the different ways the WH engineers designed these systems. With each set of components, regulations, and market forces they had to adjust their approach.

And @Racinbob’s observations are absolutely valid--“it may well have been altered somewhere along the way.” Heck, I’m as guilty as any PO since I’ve replaced damaged wiring without sticking to “original” colors and I’ve upgraded a non-solenoid system to solenoid. 

 

 

I'm very guilty of it too Don. I just shake my head when I look at the diagram for my 1976 (let alone the earlier tractors) and then the one for my 2005. It can really intimidate someone who isn't adept at reading schematics. The Demystification Guide is an excellent tool but even with it some electrical knowledge needs to be there. I did the same solenoid thing to my (7)854 as well as completely rewiring my 76. I basically ignored any color code. I'm guessing a diagram for a 66 or 67ish machine would be closer now. So far my 2005 hasn't given me any problems yet  but when it does it will be simplified as well. Actually, we both have given good examples as to why I usually refuse to offer electrical from a distance. 

[Handy Don 12,232]

5 hours ago, Racinbob said:

usually refuse to offer electrical from a distance. 

Over the past year, as a favor to a nearby non-profit, I’ve become the maintainer of one of those green lawn tractors.

The first contact, though, was them trying to get me to diagnose the problem over the phone. “Nope,” says I, “hands on is the only way to really get to the bottom of the issue.”

A clumsy operator had managed to kick the wire to the starter solenoid disconnecting it. I would have never suggested looking for that over the phone but in person it was less than a minute to fix.

Latest was them leaving the key in the ON position and hearing “Oh, does that really matter?” when the battery was toast.

Edited February 14 by Handy Don

[JoeM 7,874]

Just about every horse I get has some part or in few cases all electrical circuits deleted. 

The last one had the battery control wire (that was wrapped onto the positive terminal no fuse either), skinned and twisted into ignition switch bypassing the amp meter. The PTO circuit was bypassed the same. I figure the fuse delete cause some of the wire melting I found in what was left. 

I guess it was the wiring safety delete option. 

Some just want it to run. 

[953 nut 55,237]

On 2/13/2024 at 10:57 PM, Pat Marchwick said:

I will get that tomorrow.

but is there a sequence of switch activation to get the ok to activate the solenoid?

[Lee1977 6,660]

He gave the model no. in the first post  4120oe02  It's a 520 -H 1991 model.

[Racinbob 11,081]

24 minutes ago, Lee1977 said:

He gave the model no. in the first post  4120oe02  It's a 520 -H 1991 model.

Note that the post was edited yesterday. It wasn't there when we all started this.

[953 nut 55,237]

On 2/13/2024 at 8:10 PM, Pat Marchwick said:

if I put my idiot  light clamped to the ground of the battery when I put my test probe on the

#1 in sequence?, the PTO safety switch I should have power going in  and if the pto disengaged going out to

#2 in sequence?. The parking brake switch, if brake is on power should be sent to next switch

#3 in sequence?, the seat switch, if seat switch is depressed power should go to the next switch

#4in sequence?, neutral safety switch, if transmission is in neutral power should go to the next switch

#5 in sequence?, low oil switch, if above allowed low level power should go to the next switch

#6 in sequence?, air filter restricted switch, if air filter is clean power should go to the next switch

now if all switches are proper it is ok to send power to solenoid to start the machine

The diagrams in this link will show you how power gets from the battery to the starter and what allows the ignition to operate while starting and in operation.