1991-1997 520H demystification question

[Jake Collie 3]

I was looking at the demystification schematics for a 1991-1997 520H and it doesn't look right to me. The wiring diagram is shown on page 7-98 and the starter motor circuit is shown on 7-99. The starter motor circuit shows an orange wire going from the I on the switch to the seat switch. The wiring diagram shows an orange wire coming from the I on the switch going to the kill relay and then on to the coil if the kill relay is energized. I understand the starter motor circuit but the wiring diagram itself has me confused. Is the wiring diagram correct? If it is correct, how does anything get power in "run" when the only power coming out of the switch goes to the kill relay and then goes nowhere because the kill relay can't be energized? I am a pipefitter by trade not an electritian so please be gentle on me. Thanks.

[Save Old Iron 1,568]

Jake, a good question. It does present itself as a little "excessive", doesn't it?

I have included two pics showing the internal "mapping" of ignition switch contacts for a switch used in the 520 tractor.

In the RUN position,

please note the 12 volt power is not yet being sent down the "S" terminal to the starter circuit.

When the ignition switch is turned to the START position

the "S" terminal and the "I" terminal are both powered with 12 volts from the battery.

(click to enlarge)

From the schematic above

#8 is always hot if the battery is connected to the tractor

#6 is always hot if the battery is connected to the tractor

#1 is always hot

# 2 is hot when the ignition switch is in the RUN position AND in the START position

#4 becomes hot when all the safety switches are satisfied - this gives the switching relay the POTENTIAL to pass power to the Start Relay if all the safety conditions are satisfied

Operator turns ignition key to START

# 3 goes hot and # 4 STAYS HOT

# 3 going hot pulls in the contacts on the switching relay (green contacts) and makes # 5 go hot.

When #5 goes hot, the Start relay coil is now energized (the purple contacts close)

Closing the Start relay (purple contacts) sends power thru to #7 and powers the Solenoid (blue contacts)

Blue contacts close ( # 8 powers thru to # 9) which applies power to the Starter motor and engine now cranks.

I question the need for the Start relay - It is probably an additional safety feature someone felt was needed. It may have even been a marketing ploy as in "our tractors are safer than your tractors." Who knows!

[groundhog47 347]

Jake, a good question. It does present itself as a little "excessive", doesn't it?

I have included two pics showing the internal "mapping" of ignition switch contacts for a switch used in the 520 tractor.

In the RUN position,

please note the 12 volt power is not yet being sent down the "S" terminal to the starter circuit.

When the ignition switch is turned to the START position

the "S" terminal and the "I" terminal are both powered with 12 volts from the battery.

(click to enlarge)

From the schematic above

#8 is always hot if the battery is connected to the tractor

#6 is always hot if the battery is connected to the tractor

#1 is always hot

# 2 is hot when the ignition switch is in the RUN position AND in the START position

#4 becomes hot when all the safety switches are satisfied - this gives the switching relay the POTENTIAL to pass power to the Start Relay if all the safety conditions are satisfied

Operator turns ignition key to START

# 3 goes hot and # 4 STAYS HOT

# 3 going hot pulls in the contacts on the switching relay (green contacts) and makes # 5 go hot.

When #5 goes hot, the Start relay coil is now energized (the purple contacts close)

Closing the Start relay (purple contacts #6 powers thru to #7) and powers the Solenoid (blue contacts)

Blue contacts close ( # 8 powers thru to # 9) which applies power to the Starter motor and engine now cranks.

I question the need for the Start relay - It is probably an additional safety feature someone felt was needed. It may have even been a marketing ploy as in "our tractors are safer than your tractors." Who knows!

That's about the most thorough and excellent answer one could ask.

[Jake Collie 3]

Thanks for the very detailed explination. I don't think I stated my question very well though. While the starter motor circuit, spark circuit in start, spark circuit in run... are very clear in the demystification schematics, the entire wiring diagram page appears to be missing a wire. My demystification copy, which was revised on 4-03, needs to show a wire going from the right side of the kill relay contacts to the wire going to the right side of the seat switch. Without this wire, there can be no power to any of the switches or relays. I found this out by tracing the wires on my unit. Maybe there are newer versions of the demystification guide that have this error corrected. Thanks again for the detailed explination.

[Save Old Iron 1,568]

Jake, this would not be the first time someone found an error with the Demyst guide. Wire color discrepancies are the moist frequent issues.

The diagrams listed after the main schematic are the ones I have used in the past to troubleshoot with folks having 520 issues. These "function" schematics seem to be correct and the one for the 520 start system certainly makes sense to me the way its drawn.

If you can take post a snapshot of the two areas in the main schematic where you believe the problem exists, it might save me some time and strain on the eyeballs.

[Jake Collie 3]

Save Old Iron,

I am sorry but I am a little computer illiterate and can't seem to figure out how to post the page I want. For those of you that have a demyst guide, revised on 4-03, please look at page 7-98. I have it saved in my documents electronically and it is on page 442 of 546. If you look at the "I" on the key switch you will see 1 wire coming off and going to the contacts side of the kill relay. This 1 wire also goes to the IGN part of the indicator light module. The way they have it drawn, there is no way for power to go anywhere else in the circuit as this 1 wire is going to the contacts of a non-energized kill relay which is "dead ended". There needs to be another wire connected to the original 1 wire at the kill relay contact and it needs to be routed to the wire that connects the seat switch and the contacts on the switch relay. With this extra wire connected in this way, power is allowed to go to the rest of the circuit, allowing it to function as intended. I am not the best explainer in the world but hopefully you can see what I mean by looking at the main schematic. I do agree that the "function" schematics do seem to be correct. Hopefully this will help someone else who is scratching their head as I was trying to figure out the 520H main wiring schematic.

[Save Old Iron 1,568]

Let's try this

The wiring I believe you refer to is part of the IGNITION KILL circuit. I was looking at it from the STARTING circuit perspective.

The kill relay appears to be wired properly. Even thought the relay has two contacts, only one contact is need - the contact to pass thru 12 volts to the ignition coil.

When the ignition switch is in the RUN position, both points labeled #1 are powered up. The kill relay is not powered up at this point unless

#3 (operator is in the seat) is true

OR

#4 (PTO is disengaged AND the direction lever is in Neutral) is true.

If either of those two conditions are true then #2 will receive 12 volts and power the Kill relay coil. With the kill relay energized, the contact inside the relay will come off the "unused" terminal you point out and engage with the terminal that has 12 volts from the ignition switch.

Summing up, there is no need to have a wire on the unused terminal of the kill relay.

Hope that takes us a step further toward answering your question.

[Jake Collie 3]

Save Old Iron

This is the drawing I am referring to when I say there needs to be a wire added. I didn't mean that there was a need to physically add a jumper wire to make the unit work. I was referring to the above wiring diagram that needs to have another wire drawn in it to be correct. I know it is small but if you look, there is only 1 wire coming off of the "I" part of the key switch. It goes to either the dead ended contact on the kill relay or to the IGN indicator light. I believe there should be another wire drawn in on this diagram to connect the "I" wire to the wire going between the seat switch and the top contact on the seat relay. As you have stated, the "function" diagrams seem to be OK but this main wiring diagram needs to be updated.

[Save Old Iron 1,568]

the wire going between the seat switch and the top contact on the seat relay.

I don't think you meant "seat relay".

There is a switch relay, a kill relay and a start relay.

I figured the "in for a dime, in for a dollar" rule applies here. We might as well keep pecking at this one till we get it right.

[Jake Collie 3]

You are right. I meant switch relay.

[Save Old Iron 1,568]

I believe there should be another wire drawn in on this diagram to connect the "I" wire to the wire going between the seat switch and the top contact on the seat relay I meant switch relay.

in this manner ?

red arrow points to the addition you suggest (shown by a blue line added to the schematic)

are we getting closer?

[Jake Collie 3]

YES! That's what I was talking about. What do you think?

[Save Old Iron 1,568]

Good call Jake. Thanks for hanging in there with me thru all the questions.

You are correct in regards to "no power to the relays" in the original schematic. I deleted all the superfluous wiring to our conversation and ended up with this

(click images to enlarge)

I do know for a fact the 520 ignition coil is powered up with the ignition switch in RUN. As you can see, tracing the red wire from the ignition switch to the KILL RELAY shows the red wire is dead ended to the relay. This means the KILL RELAY coil must receive power over the green wire to allow the ignition coil to receive power while the ignition switch is in the RUN position.

Note the smaller inset drawing I placed showing the functional START schematic. The thin blue dotted line shows the location of the connection you questioned in your first post. The total wire length for that connection is represented by a dotted pink line.

Correct schematic representation of the live circuits when the ignition switch is in the RUN position are shown below. All circuits with 12 volts present are represented in red.

Looking closer at the original Demyst Guide schematic, the "I" wiring does cross the "seat switch line" but the schematic does not show a "dot" which would represent both wires as electrically connected.

To correct the original schematic, add a dot at the wire junction called out below.

[Jake Collie 3]

Save Old Iron

I think it is me who needs to thank you for hanging in there with me! I'm glad we (you) figured it out for me. There was a lot of head scratching on my part trying to figure this one out. Who would have thought a little dot would make such a big difference? Hopefully this will help out anyone else looking at the main wiring diagram. It appears that looking at the "function" diagrams will be the way to go in the future for me. There is a lot less going on with them. Thanks again, Jake.

[Save Old Iron 1,568]

You should call this into Toro.

Maybe you could snag a T-shirt out of the deal !!

[Jake Collie 3]

Save old iron

It would make me happy if you would take all credit and call it in to Toro. My wife says I have too many

t shirts anyway. Thanks again for all the help.

[Save Old Iron 1,568]

Jake, I gave Toro a heads up on this issue via email.

We will see what comes back

Dear Chuck,

Thank you for contacting Toro Customer Care. We are working on providing you with an answer to your email. Due to high seasonal volumes, it may take up to two business days for us to respond. Please refer to Case #2421981 if you need any additional assistance.

No answer yet, and of course the email was sent three days ago.

[Jake Collie 3]

SOI I'm interested to find out what they say. When you find out please post their response. Thanks.