1811 CCC/Engine dies when pto is engaged

[cfrock]

I recently bought a 1811 Cadet from a woman. She told me that it wouldn't start and a friend of hers said that it had a bad coil in it. I pulled it apart and replaced the coil and it started right up. When I engaged the front pto the motor dies just like you would turn the key off. Turn the pto off and the motor fires up again. I bought another used pto and swapped them but it still does the same thing. I checked the ignition switch terminals and found one terminal almost rusted away so I bought a new switch and put that in and it still does it. Sounds like to me that when you turn the clutch on { and it does start & turn] it produces a dead ground to the ignition. But I am at a loss of where to look for it. Anyone have any ideas??

 

[mhomrighausen]

Charles F. Just a shot in the dark here. The PTO circuit hasn't been "hot-wired" in anyway has it? By that I mean that someone may have tried to override the switch that diengages the electric pto when the tractor hydro lever is moved to the reverse position so that the mower will keep running while the tractor is backing up. I'd check the wiring on the swtich area of the hydro lever and make sure that nothing has been wired so that the mower stays running while the tractor backs up. A mechanic thought that he was doing me a favor by doing just that on my 782D when I first got it. The tractor ran great... for awhile. Then it started doing the same thing as yours. I now run the switch and system to the way the factory set it up and haven't experienced any problems since. Myron Bounds helped me solve that problem. And Myron said that I was lucky that I didn't burn out the electric pto on the tractor.

Try HERE to see if they have a wiring diagram for your tractor. (Hope this helps.)

 

[bpientka]

Make sure the seat safety switch is working. On my 1711 if you tip the pto switch while not seating on the tractor the motor dies. Is you quickly switch it back the tractor will keep running.

Good luck

 

[cfrock]

Marlin & Bernie, Yes the wires that go on the micro switch for the reverse stop mower when backing up have been removed and tied together. I think that I will put them back on and see if it makes a difference. As for the seat safety switch that also has been unhooked and I do not know how. If the micro switch doesn't fix it I will have to go further with the seat safety switch. Thank you both for your input. Chuck

 

[mhomrighausen]

Good morning, Charles and Bernie. On our 782D the safety switch on the seat has been tied off and doesn't affect the mower deck's pto switch. I dont' mind that one near as much although I don't make a habit of getting of a tractor with a running mower deck.

 

[rbedell]

Charles:

There are two different Wiring Diagrams for the 1811, depending on the Serial Number range. What is your Chassis Serial Number?

 

[jchamberlin]

Marlin --On my older 782 when the PTO is switched ON the ignition receives its power from the seat switch; when the PTO is OFF, the ignition receives its power from the PTO switch. See diagram below.

Without having a later model 782 to examine, I can only surmise that the N/C contact of the Reverse Relay allows the starting circuit to pull in the PTO to remind the operator to move the switch into the OFF position. Otherwise, the rest of the circuit appears to work by "arming" the N/O contact of the Reverse Relay with the output of the N/O Seat Switch. When the PTO is switched ON, the relay is latched until either the seat switch is opened or the the tractor is put into reverse. I imagine the 1811 is wired in a similar fashion. See diagram below.

When someone hard-wires the Seat Switch, they disable one leg of a parallel safety circuit on either tractor. The earlier version is a little easier to understand since there are no relays to "latch," that is, feeding the output (once energized) back in as the input to keep the relay energized even though the original source of power has (intentionally) been removed.

Again, my analysis of the later version of this circuit is based only on analysis of the diagram, I don't have the relay in my hands as it is wired into the tractor, so I'm not able to verify the identity of the terminals on the relay itself.

Charles, I hope you find the discussion helpful.

 

[rbedell]

The original inquiry was for 1811. Why are you guys talking about 782's? The PTO circuitry is DIFFERENT.

 

[jchamberlin]

Holy Schni-kees, Batman!! Roland you are correct: the 1811 is certainly wired differently than either style 782, and the two versions of the 1811 are wired more differently from each other than they are from either of the 782s, although its development can be traced across all four models.

The earlier 1811s, before S/N 757,000, are wired a lot like the later 782 models, except that they use a Seat Relay to ground out the magneto. The Seat Switch itself is Normally Closed, unlike the earlier 782 or the later 1811s (757,00 and later). The Seat Relay is energized by the the RELEASE of the Seat Switch, and the Seat Relay, when energized grounds out, or "kills," the magneto.

Note that the Seat Switch itself gets its power from the N/O terminal of the Reverse Relay, which in turn is fed by the "R" (Alternator) terminal at the key. This arrangement places the Reverse Relay in SERIES with the Seat Relay --both the Seat and the Reverse circuits are needed for the tractor to run or the PTO to operate. The PTO itself is dropped when the N/C Reverse Switch trips the "latch." See below:

The later model 1811s implements the same logic for the Seat and Reverse circuits in a much simpler fashion: a N/O Seat Switch is simply inserted in the latch in series with the N/C Reverse switch. In this arrangement, getting out of the seat no longer shuts off the motor: it simply drops out the PTO, which seems like a much saner arrangement to me.

I hate it when the seat switch kills the motor, even though I know that its purpose is to preserve my safety.

So, thank you Roland for giving me the opportunity to educate myself, and hopefully give Charles some proper guidance for his 1811. I apologize to all for muddying the waters. I have always had a hard time staying on topic (a fault some owner/moderators have occasionally pointed out).

Charles, if you can't find a serial number on the tractor, one way to answer Roland's question is to check to see how many relays are on your tractor; if you find two it is an earlier version of the 1811, if you only find one (and no tell-tale wire harness butchering) you likely have the later version.

 

[mhomrighausen]

Roland B. I was merely referring to the 782D and the safety switch mechanism being "hot-wired" so that could be a starting point for Charles F. I already knew the wiring was different. I didn't see any wiring diagrams when I did a quick check in the wiring diagram section or I would referenced that.

 

[cfrock]

Hi Guys, Thanks for all of the info comcerning the problem with my tractor,s PTO. I have rehooked the reverse safety switch and the seat safety switch and the problem still remains. I took another PTO switch off of another one of my tractors that I know worked and swapped switches just to make sure that it wasn't the switch causing the problem. Well it wasn't. It still will not work. Even with the motor not running and the key turned on when you engage the PTO the clutch engages on and when you return the switch to the run position the clutch turns off. It does the same thing with the motor running.
I am going to get a friend of mine to look at the wiring diagrams that you put up and make a couple of rough drawings of them to refer back to. I am not electric oriented and cannot make much sense of them.
To answer a question about how many relays it has, it has only one. This is the only part that I have not replaced with another one yet.

 

[jchamberlin]

Charles --It sounds to me like something isn't wired correctly on your tractor. The position of the PTO switch shouldn't affect the operation of the motor on your tractor, if you have the later model 1811. The only way the motor on your engine should turn off is if the key is placed in the "OFF" position. The seat/reverse interlock is only supposed to drop out the PTO, not the motor, on your tractor.

Your diagnosis is correct, something is grounding out the magneto if the motor is dying.

If it isn't the key, what can it be?

I would:

(1) verify that the key switch operates as described in the diagram above for 1811 tractors S/N 757,000 and above
(2) verify that the PTO switch operates as described in the diagram above (I believe the "START" position for your PTO switch is momentary)
(3) If both devices check out OK, then I would start tracing wires to be sure that they go where the diagram says they should go.

Before I did any of the things I list above, I would make sure all my grounds were good.

My frustration is that I can read the diagram; but I can't see your tractor, and I think the problem is on the tractor.

To repeat myself, the only way your tractor's motor should turn off is if the "M" terminal at the key is connected to ground.