1991 520H Seat switch

[mmmmmdonuts 274]

I have a 1991 520H and when I engage the PTO it dies instantly and I believe it is the seat switch but I am not positive. The tractor does fire up instantly but I don't remember if I actually need to be sitting on it or not to start. I was trying to diagnose it and fix it but I am not sure if I am doing it correctly. It has the 3 terminals Brown, Red, orange I believe. I have been looking in the dymystified guide and I am not sure if I should be looking at 1990 or 1991 or if it is some hybrid of the two. 

 

Any thoughts or suggestions? Where would the PTO microswitch be if I had one? 

Edited June 1, 2019 by mmmmmdonuts

[gwest_ca-(File Mod) 11,102]

There are 2 pto switches next to each other at the right end of the battery so the pto linkage can control them. One controls the starter and the other controls the ignition.

 

The orange and brown wires are connected when the operator is in the seat and with the pto ON the seat switch powers the ignition so your thinking is correct. The 3rd seat switch wire controls the idiot lights and has no effect on tractor operation.

For testing purposes add a jumper to the orange and brown wires. If the problem disappears the seat switch is not being activated. Could be a bad switch or perhaps the operator in the seat is not heavy enough to close the switch.

It can be more complicated as these switches control a series of relays to get the job done but you have to start at the switches.

 

Garry

[mmmmmdonuts 274]

Thank you that's what I will do to get started. I was just trying to figure out what wiring diagram is closest to being correct.

[gwest_ca-(File Mod) 11,102]

Post all the numbers off the tractor data decal and will try to see if your have an early production 1991 tractor. That may be close to 1990 models where there could be carryover.

The brown and orange show for both years at the seat switch.

I think UV light bleeds some of the colors out off the insulation. Sometimes one has to go to a portion of the wiring that has been covered to see the true color. Red has to be the worst and most colors have some red in them.

 

Garry

[mmmmmdonuts 274]

It looks like it isn't the seat switch. I shorted the orange and Brown together and nothing. Should I short all 3? The tractor still started though. Now I started cleaning wires and now can't get it started.  It is definitely a red and orange wire. I am surprised being under a seat that there would be that much UV. 

 

I'd is: 41200E01      14335

[gwest_ca-(File Mod) 11,102]

The tractor is a 1990 model and the latest 520-H serial number recorded so far.

Click on the picture to see it.

 

The brown joined to the red should only put the seat switch light on.

The brown joined to the orange should give you battery voltage at the ignition coil with the key in Run and Start

The brown gets it's power from the pto switch that controls the ignition.

The ignition pto switch gets it's power from the yellow going to the I (eye) terminal on the ignition switch.

The other pto switch controls the starter circuit.

 

Have identified the switches on one of the Detailed wiring diagrams

 

Garry

 

[mmmmmdonuts 274]

Thank you for the information. Maybe it was a leftover model year on the lot. Didn't get a chance to look at it again today with tons of thunderstorms but hopefully come this week/weekend.