mtd electric pto circuit operation

[Deere2me]

Wow.... not sure how you've gone the past 20 years without seeing at least one.

In those, power through the PTO switch is passed through the hold in relay which feeds power through the PTO relay, energizing the clutch. There's 2 circuits to the hold-in relay, one through the safety switch system for operator presence (Seat Switch, Reverse Switch) which gets its power from the clutch relay (draws from the same circuit that powers clutch) - when safety switch activates opening the circuit, the hold in relay lets go, so the clutch relay lets go, and on older style units you have to push in and pull out the electric clutch switch to re-energize. There's some machines where it will re-energize if it is only the reverse switch that trips the safety - so you go in reverse, mower stops, when you go back to neutral or forward, mower starts again. (but if you come out of seat, even with parking brake set, mower shuts off and stays off until you re-set the PTO switch.)

It's really pretty simple system, but it takes a little brain power to wrap your head around how the circuit works from reading a diagram - but once you understand it, it isn't hard to diagnose.

Wow, really?? Wow ?..... Not sure either, just know I haven't. I might could add that I don't recall ever having read about that system on any other board, INCLUDING Bruce's old forum.

The key words being brain power whaddayathink!

[Deere2me]

maybe this link is more complete.
http://web.ncf.ca/da229/WHITE-13BT696H190_LT-185_(1999).pdf
or at bottom of page here
http://search.cartserver.com/search/ods ... &go=Search!

New switch just arrived so if all works ok maybe it's just academic for now. It does not seem to be like the reverse override where a relay gets energized manually and then feeds itself through another relay until that other relay is deactivated because of a lever change (leaving reverse). Guess I will have to duplicate the circuit with the various components to figure it out.

So, after perusing the diagram, it appears the system should work as BG described. I will add, however, that the PTO circuit ( switch and relay contacts) can still benefit from the addition of a diode in the circuit.

[KE4AVB]

All they are doing is using a safety relay to switch from 12 volts to ground (relay is energize to to quickly de-energize the PTO relay which appears to have a slight delay in release if not done so). The PTO switch has to be cycled in order to re-energize the PTO relay. Now the PTO switch itself could have make before break contact setup too so the relay doesn't drop out during the time switch turn on to energize the PTO.

[38racing]

Ok, the new switch arrived and so did the friend who has the same setup (and helps that he is an electrician).We did confirm that old switch was dead but I did not know how the switch worked. He told me there is off and on but also a momentary 'engage'. We tested new switch and at first he was baffled as we got a continuity in on but the momentary made no difference to any tabs continuity. He said to look near the mower switch location for instructions. Nothing helpful and then for some reason from way back in my brain from using maybe a mower like this I pulled on the toggle of the switch and then it moves into the momentary engage position . Needless to say the friend was a little embarassed about forgetting that detail. So now I know how the switch really works and will look again at the circuit.

[38racing]

All they are doing is using a safety relay to switch from 12 volts to ground (relay is energize to to quickly de-energize the PTO relay which appears to have a slight delay in release if not done so). The PTO switch has to be cycled in order to re-energize the PTO relay. Now the PTO switch itself could have make before break contact setup too so the relay doesn't drop out during the time switch turn on to energize the PTO.

And this all makes sense now when I know how the PTO switch actually works and contrary to what I thought it is a case of a momentary switch activating a relay now who's closed circuit will provide the 12v source to keep it activated after the original momentary 12v is gone. And the connection to ground is the relay coil contact that just had the 12v removed from it.