Walk behind unit electrical problem

[Richie F]

I'm working on a model SW36A14FS
s/n J6100114

The owner of this machine has disconnected/by passed all safety switches.
With the engine running when the PTO is engaged the engine shuts off.
Unplugging the ground wire for the Magneto the PTO will function properly.
I realize something is still in the circuit to ground out the Magneto when using the PTO switch.
Both harnesses are in good shape. No chafing anywhere.
I tested the resistance of the PTO coil and have 3.3 ohms.
Also tested the diode and it's good.
I do have the wiring diagram for this machine.
Thanks

 

[tom3]

Some of these safetys are not just make or break contacts. Maybe a third wire deal to prove the circuit is intact. Maybe a set of switches in series. Have to dive into the schematic and see where the problem is I suspect.

 

[Richie F]

Some of these safetys are not just make or break contacts. Maybe a third wire deal to prove the circuit is intact. Maybe a set of switches in series. Have to dive into the schematic and see where the problem is I suspect.

Thanks for your interest in this problem.

 

[bertsmobile1]

I am guessing that it has a manual clutch.
If not then there will be safety switch built into the PTO switch.
Hope you are charging MR D Head by the hour to sort out his mess.

 

[Richie F]

I am guessing that it has a manual clutch.
If not then there will be safety switch built into the PTO switch.
Hope you are charging MR D Head by the hour to sort out his mess.

First off Mr D Head is a personal friend of mine. ( I know what you're implying) and no money is involved in this repair.
Second if you would look at the wiring diagram the clutch is power by electric.
Thanks

 

[geelee]

a wiring diagram is can be found on partstree under the model and serial number for that machine

 

[tom3]

Simple solution would be to put a momentary contact switch on the mag. kill line to ground. No big voltage or current in this circuit. Bypass all the stuff. Nice big red button on the dash. Probably not legal in all 50 states though.

 

[NorthBama]

I would use an OHM meter and find what is connecting the kill wire to ground to kill the engine when pto switch is pulled to engage the clutch.

 

[bertsmobile1]

In which case my first reply is still valid, the PTO switch will have several safety circuits running through it and they are very difficult for people with no idea about what they are doing or basic DC electronics to bypass properly.
As you might have already guessed I do not have much time for people disabling safety switches, regardless of the fact I do not believe in them. The best safety switch is between your ears.
Apart from seats on ZTR's which were too sensitative there is however little reason to dissable switches unless the person has a serious dissability , as none of them prevent quick & efficient use of the mower.

We have had this discussion on here 100 times before and just like gun regulations it is very polar with both sides fairly well entrenched in their ideas.

To be frank, I would rather see mowers made safe to use with guards and not any of the switches bar the seat switch or some other dead man device that kills the machine stone dead the instant there is no one in the seat or the operator has a seizure / heart attack etc.
If we came across people on a daily basis missing fingers , hands , toes etc from careless use of their mowers then it would be reinforced in our minds that these things are very very dangerous tools.
But unfortunately all of the safety gear installed makes it next to impossible to injure yourself so people use their mowers in a totally brain dead fashion, in a dangerous manner in dangerous situations then sue the factory when they succeed in doing damage.

And I am not trying to be preachy here .
I have a customer with Lupis so she can hot hold a bail for any length of time.
The solution is a pin that holds the bail closed tied to a string around her wrist so if she falls over the mower stops , not bypassing the bail all together.

So if you have the wiring diagram just follow the kill wire back from the coil to where ever it grounds, and there will be a lot of places where this can happen.
If necessary print it out a couple of times, pinch a coloured pencil from one of the kids and trace over the kill wires for each situation or use different coloured wires for PTO on & PTO off
IF there is no pin out for the PTO switch then pull it out and measure across the contacts.
It is a simple sliding contact switch that connects left to right and generally all of the middle row will be tied together.

 

[Luffydog]

Put everything back in place all safety switches and see if the problem goes away. Also at 3.3 ohms is high for the clutch so soon as you apply the clutch it draws out all the battery and could be your problem. Replace the safety's then go from there one leads go to the others failure.