Simplicity Zero Turn Electrical Problems

[JD45]

Simplicity model# 5900774
B&S model# 44P777 Type 0159-G1

Start up engine and pull pto switch- engine dies
Bypass seat switch- pull pto switch- engine dies
Checked all safety switches for continuity- all good
Checked and cleaned coils- good spark- added new plugs
Checked continuity from each switch plug back to harness plug for engine- all good
Pulled both kills wires on engine coils- engine ran fine and blades engaged like they are supposed to.
Plugged kills back in- started engine and pulled pto switch- engine starts to die- pushed pto back in and engine picks back up.
Pulled kill wire on right side coil- (long wire) left side wire still hooked up- pulled pto engine runs and blades run but engine sounds like crap- still have spark both coils.
Pulled kill wire on left side coil- (short wire) left right side kill wire hooked up. Pulled pto - engine dies.
I am guessing I have a bad diode on the coil wire?
Fuel solenoid works fine and battery is good.

 

[NorthBama]

check diode with Ohm meter if your not sure about it

 

[JD45]

Well.... diodes not the problem. Buddy had a new harness for me to try on it. Same problem as soon as I pull the button on the pto I lose all power to the engine- push the pto back in and engine picks right back up.

 

[Rivets]

Have you tested the PTO switch?

 

[JD45]

Have you tested the PTO switch?

Sure did, it tested fine- but I went ahead and swapped it with a switch that I know is good- no difference. Beginning to think it has something to do with the 2 switches on the parking brake or the seat switch- put a jumper wire between the 2 wires on the seat switch plug- trying to work out what the 2 brake switches do for sure now- pretty sure one is for the solenoid and the other is for the pto looking to find a wiring diagram now .

 

[bertsmobile1]

Without you supplying the full model & serial numbers we can only give very general advice.
If the brake switch has 4 wires, two will be the kill wires ( usually the same colour ) and the other pair are the cranking circuit .
The kill wires are a ground only circuit & the cranking wires are a POWER circuit , if you accidentially cross them & send battery power to the coils you will kill them stone dead .
If the seat switch plug is flat with 4 wires then it might have a shorting contact in the mower plug to prevent idiots removing the seat switch.
Start the engine , set the parking brake & get off the seat.
The engine should remain running .
ZTR's get complicated because of the lap bar switches and the tendency for the use of kill relays.
Engine kill is a ground circuit & you have 3 of them
Lap bars + parking brake
Seat switch + parking brake
PTO switch + Seat switch.
The diagnosis tests that may help isolate your problem is to try all 3
Leave brake on and move lap bars engine should stop
Set parking brake & get of seat, engine should remain running
You already know the result of the 3rd, your engine dies
If the 2nd test fails then it points very strongly to the seat switch , the seat switch relay ( if fitted ) or the WIRES connected to the kill switch.

 

[JD45]

Model# 5900744
Seriel# 2013903097
So far I have narrowed it down to the seat switch which is a 2 wire plug or one of the 2 brake safety switches i think one of them might be shorting out. I believe one is brake + solenoid and the other is brake + pto not sure without ripping out a bunch of wires. Trying to find a schematic but so far have only found a drawing. Thanks for the help.

 

[Fish]

The parts manual has a wiring schematic.

Results

www.simplicitymfg.com

 

[JD45]

The parts manual has a wiring schematic.

Results

www.simplicitymfg.com

Thank you

 

[JD45]

Finally got it- some knucklehead swapped the plugs around on the 2 parking brake switches. Once I put them right and did a little work on the seat switch she now runs like a Cadillac!! Thank you to Fish also for finding the schematic it was a life saver. Got me where I needed to be.. and thank to everyone else for the help and the ideas.