mtd electric pto circuit operation

[38racing]

I have a white(mtd)1999 lt-185 , model 696 for which I have the wiring schematic. I am trying to understand the electric PTO circuit. It involves 2 relays. One I think is just used to direct alternator power directly to the clutch . The other is the safety relay to shutoff pto if unit is put in reverse or operator gets off the seat. When the pto switch is in the on position and key in run there is a path from battery to the hot side of the clutch(blue/wht). The clutch green ground wire always has a path to ground. My conclusion is that should the seat or reverse switch supply a path to ground then a relay is activated which 1. deactivates the relay which was allowing the alternator direct to the clutch and 2. put 12v to the ground circuit of the clutch . I know that idiot lights on older cars were turned off by applying 12v to both sides of the bulb but I can't remember if the one side still had a path to ground. Schematic is on page 14 of this pdf .
web.ncf.ca/da229/WHITE-13BT696H190_LT-185_(1999).pdf

[HondaG100]

I am no electrical diagram expert but your analysis appears to be correct except for supplying 12 V positive to ground. If you did that then nothing would work anywhere since all electrical potential would be the same everywhere on a unit that uses the frame as a negative. There will always be a component of some sort between battery positive and the frame.

[Deere2me]

Is there a question in yer post somewhere????
Since you have a wiring diagram, and yet, still seem to be baffled, here's a tip fer ya: print out a couple copies and get ya a couple of diff. colored pens. Then trace the circuit you are working on, or different parts of it, in different colors. I use Pilot Gel G2 ball point pens. Some mfgs actually use that system of diff colors to isolate the circuits, makes it a hellova lot easier to understand, especially for the electrically challenged amongst us. Try it!
If it will help, you can get a complete set of little animal stickers on fleabay to mark the wires, sort of like Garanamals!

[KE4AVB]

A question here while I'm thinking on the circuit operation. Do you need to cycle the PTO switch after a reverse operation? If so then we have a make before PTO switch and I should be able to explain the operation.

[38racing]

Is there a question in yer post somewhere????
Since you have a wiring diagram, and yet, still seem to be baffled, here's a tip fer ya: print out a couple copies and get ya a couple of diff. colored pens. Then trace the circuit you are working on, or different parts of it, in different colors. I use Pilot Gel G2 ball point pens. Some mfgs actually use that system of diff colors to isolate the circuits, makes it a hellova lot easier to understand, especially for the electrically challenged amongst us. Try it!
If it will help, you can get a complete set of little animal stickers on fleabay to mark the wires, sort of like Garanamals!

actually done all that except the stickers . question was implied. is my analysis correct ?

[38racing]

A question here while I'm thinking on the circuit operation. Do you need to cycle the PTO switch after a reverse operation? If so then we have a make before PTO switch and I should be able to explain the operation.

no reverse override. if i read it right when the reverse or off seat ground disappears then relay will just remove the 12v and clutch will regain power. should have the new switch today.

[38racing]

I am no electrical diagram expert but your analysis appears to be correct except for supplying 12 V positive to ground. If you did that then nothing would work anywhere since all electrical potential would be the same everywhere on a unit that uses the frame as a negative. There will always be a component of some sort between battery positive and the frame.

my thought too. carb solenoid going off would kill engine.

[Deere2me]

Is there a question in yer post somewhere????
Since you have a wiring diagram, and yet, still seem to be baffled, here's a tip fer ya: print out a couple copies and get ya a couple of diff. colored pens. Then trace the circuit you are working on, or different parts of it, in different colors. I use Pilot Gel G2 ball point pens. Some mfgs actually use that system of diff colors to isolate the circuits, makes it a hellova lot easier to understand, especially for the electrically challenged amongst us. Try it!
If it will help, you can get a complete set of little animal stickers on fleabay to mark the wires, sort of like Garanamals!

actually done all that except the stickers . question was implied. is my analysis correct ?

From what I can tell, no. I don't see how you can put 12V+ straight to ground without cooking the wiring. Can't access the pdf link you supplied. But most , if not all of the electric clutch setups I've worked on, route the 12V + straight from the keyswitch thru the PTO switch and then on to one side of the clutch pigtail. The other side of the pigtail going straight to ground. There may be a fuse in the circuit and there may be a diode across the circuit, but thats pretty much it! If it doesn't have a diode, you should put one in, it will make the PTO switch last a lot longer.All the safety relays generally control starting/running etc. As I said, I've not run across a unit that routes the clutch power thru a safety relay to control it's operation.

[bgsengine]

From what I can tell, no. I don't see how you can put 12V+ straight to ground without cooking the wiring.

Can't really - not without a bunch of expensive electronics. So, you're right on that.

Can't access the pdf link you supplied. But most , if not all of the electric clutch setups I've worked on, route the 12V + straight from the keyswitch thru the PTO switch and then on to one side of the clutch pigtail. The other side of the pigtail going straight to ground. There may be a fuse in the circuit and there may be a diode across the circuit, but thats pretty much it! If it doesn't have a diode, you should put one in, it will make the PTO switch last a lot longer.All the safety relays generally control starting/running etc. As I said, I've not run across a unit that routes the clutch power thru a safety relay to control it's operation.

Wow. Circuits like the O.P. have been around 20 years and more. First encountered them back in the late 80's on MTD where they use 2 relays in a pair , one relay controls power to the clutch, the other is a "hold in" relay - basically power through the hold-in relay runs power through the power relay winding - which also feeds power through the safety circuit to the hold-in relay - with that system you can have a cut-out of the clutch , such as in reverse, and when going back to forward, completing the circuit through the hold-in relay again, power restored to the clutch. Have seen them even on John Deere machines.. 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.

[38racing]

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.