318 PTO Still

Todd,
Here is my 2 cents worth. I only have a rough schematic of the 318 but it looks to be wired with both a safety circuit and a PTO power circuit. When you say there is power to the switch what color is the wire you are testing? It appears that a purple and yellow are connected together at the PTO switch (this is the safety interlock circuit) and there should be 12v there. There is also a blue wire from the time delay module. The blue wire provides power to the PTO. Is there power at the switch on the blue wire? If not, then the time delay module has shut power off for some reason. The first thing that comes to mind is the seat safety switch is open. Check power at the seat safety switch by unplugging it and see if you have 12 volts at one of the terminals on the connector. Power to the seat safety switch comes directly from the key switch. Let me know what your results are. There are others things to test and I can walk you through until we find the failure.
I just went through an odd problem on my 322 and it ended up being a short in the wiring harness. Hope yours is easier.
Let me know what the tests indicate,
Bob

Todd,

You should get the TM1590 which contains all the wiring diagrams and the theory of operation of each section, plus lots of the mechanical information you will need to keep your tractor working properly. I sent you some wiring diagram excerpts to get you started on last Tuesday the 4th, did you get them?

Below is the schematic of the PTO section.


If there is not any voltage at the PTO switch on the 415 purple wire check the F1 fuse. If you do not have a rear PTO on your tractor, there should be a jumper in X5 that connects the 730 purple wire to the 780 purple wire. The voltage on the 780 purple wire when the PTO switch is off is what initially closes the relay in the TDCM that provides power to the 760 blue wire going back to the second set of contacts on the PTO switch, and this is the source of power to the PTO coil when the PTO switch is on (it comes through fuse F2.) The 750 blue wire from the switched side of the PTO switch should go directly to the PTO coil, and that terminal of the switch should also have the 751 blue wire that illuminates the PTO lamp on the dash when the switch is on and the circuit is working. If the seat switch is off (unoccupied) for more than a second, the TDCM cuts off the PTO.

There should be no yellow wire on any terminal of the PTO switch on a 318.

Keep us posted on what you find, we can help you get this back to working condition...

Chuck

Well, time to apologize to Bob a bit here. There IS a yellow wire on the PTO switch on the 318. It does not show in the sub-section schematic I posted above but is in the complete wiring diagram and goes to the headlight switch (wire #420 - yellow) This is not the case on the 322 tractors as that yellow wire goes to a harness splice and not the switch itself.

Here are a couple of illustrations from the TM1590 and 1591 manuals that show the differences at the switch. The call-out "A" in the upper photo is the yellow wire. You can just barely see that there is another wire under it that is darker (the purple #415 wire) crimped into the same terminal of the X3 connector. X3 is on the left of both of these views, and has only one wire per terminal in the case of the lower 322 illustration.



Thanks to Todd for pointing out the full schematic occurrence of this wire -- I learn something every day here on this forum, and sometimes it is from my own mistakes...

Chuck