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Pto Drops Out When I Hit A Bump


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#1 artbuc OFFLINE  

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Posted July 26, 2012 - 05:05 AM

Hi folks! Have not been here for a long time.

Maybe 2 or 3 times during a 2 hour mow, my PTO will drop out if I hit a bump and bounce on my seat. I've recently lost a lot of weight and assumed the problem was not enough ass weight on the seat switch. I by-passed the seat switch and still have the problem. When the PTO drops out, I turn off the PTO switch to clear the relay and immediately turn it back on and the PTO works fine. Any ideas? If the PTO itself were going bad, I think it would be dropping out randomly- not just when I hit a bump.

I have a Gravely 18H which is really an Ariens GT18 with a Gravely paint job. Tractor is 20 years old with less than 2000 hours.

#2 massey driver ONLINE  

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Posted July 26, 2012 - 07:45 AM

First off because you refer to wires you must be saying that it has a electric clutch engagement for your pto not a manual one?? If you have the electric clutch then I'd suspect somewhere down the line you have a wire that has either rubbed through somewhere on the frame or has a break inside the insulation.The other possibility is that your switch or relay is going out on you.If it was the clutch itself and the winding was gone it would be gone ?? I'd check the wires first trace them all the way look for any wear spots [bare wires] etc: Hope this helps. Larry
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#3 JD DANNELS OFFLINE  

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Posted July 26, 2012 - 08:01 AM

This is a wild guess as I don't know how your machine is laid out. But on My 318 John Deere there is a relay down on the frame below the PTO and I have had the plug come loose(not clear off but backed out about 1/8") and disengauge the PTO when I hit a bump. It gets pretty hot down there and I have had to let it cool off before I could pushe the connector back on to the relay.

Edited by JD DANNELS, July 26, 2012 - 08:02 AM.

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#4 KennyP OFFLINE  

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Posted July 26, 2012 - 08:15 AM

Which tractor is this? That may help in figuring out where your problem is. Do you have a wiring schematic for it? I just fixed a neighbors mower (different brand) that had a problem with a switch not working correctly. The paddle that actuated it wasn't pushing the switch 'knob' in far enough to keep a good contact. This could be your problem. But since you are saying you have to turn the PTO switch off and wait for the relay to kick back in, I would say you have a bad wire somewhere that is shorting out when you hit a bump.
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#5 artbuc OFFLINE  

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Posted July 26, 2012 - 09:58 AM

I have a Gravely Professional 18H which is really an Ariens GT18 with Gravely badging. If you go to Ariens Parts Radar you will see it as Model 931033-004346. Yes, I have the electrical diagram and the clutch is electric. The PTO circuit includes a relay and time delay module so it you momentarily come off the seat switch the PTO will not disengage. However, once the PTO does disengage, you have to shutoff the clutch switch which (I assume) allows the relay or time delay module to reset. Then you can turn on the clutch switch and the PTO engages fine. I by-passed the seat safety switch but not the time delay module. The relay gets voltage from the ignition switch and from the time delay module in order to send voltage the clutch switch. The time delay module is, I think, solid state and should not be affected by bumps. I would not think the relay would be affected by bumps either, but I don't know. More likely a frayed wire. Thanks for your help.

PS If I can't find a bare wire, I will by-pass the time delay module. If that doesn't solve it, I will get new relay.

#6 JDBrian OFFLINE  

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Posted July 26, 2012 - 10:02 AM

Sounds like a wiring problem in the safety switch circuit. The safety switch will typically be closed when you are on the seat and open when it's empty. You have bypassed the switch but there could still be an open circuit happening somewhere else in the wiring. Since it always runs after you start up again then it's probably in the safety circuit somewhere. The PTO switch itself could also be the problem. There may be a relay involved as well. Check all the connections looking for corroded or burnt/melted wire etc.
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#7 artbuc OFFLINE  

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Posted July 26, 2012 - 11:51 AM

Think I found it. Looks like a loose connection on the relay. Also, the relay body has a plastic mounting tab which broke many years ago. Looks like one of the relay terminals may have been bouncing against the screw (and hence grounding itself) which used to secure the relay bracket. Thanks again for your responses. I'll let you know if this solves my problem.
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#8 JDBrian OFFLINE  

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Posted July 26, 2012 - 02:46 PM

Sounds like you've found a problem. You might want to go through all the connections on the tractor while you are at it looking for problems. It may save you more frustration later.




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