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Discussion Starter · #1 ·
I seem to have a problem with my JD 316 PTO switch. The yellow power wire going to the PTO switch keeps melting.
The center terminal got so hot it melted. I repaired the wire and installed another PTO switch and it happened again. I looked over the wiring harness and found the ignition plug was melting also. I then replaced the ignition and PTO switches and the wiring harness. All is good right. Wrong! Went for a mowing test run for 10 minutes and it started to melt that center yellow power wire again. Anyone have any suggestions on how to fix this problem I would greatly appreciate it. Thanks.
 

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Which model 316 do you own? The Kohler powered variety or the Onan?
 

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I would suspect you have a short somewhere in your wiring harness. Looks like you're going to have to replace it anyways so once you pull it go over it and see if you can figure where it was (which may be difficult do to the extensive melting!) Had you recently changed any wiring on your machine?
 

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Isn't there a fuse to protect your wiring from this happing. Maybe the clutch is bad, can you adjust it? Try testing it first before melting any more wires, don`t worry about the name Scag. this should help you sort things out.

http://www.ganos.com/electricclutchtesting.pdf
 

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Discussion Starter · #5 ·
K91-This is a 1978 316 with a Kohler engine.
PA318guy- as I posted "I then replaced the ignition and PTO switches and the wiring harness". I also checked the wires going to the PTO clutch and it looks fine but I will check the clutch coil.
Mower Man42- Thanks for your info, I will have to test the coil and get back to you. There is no fuse from the coil to the switch. The power seems to come from the ignition switch to the headlight switch then to the PTO switch. The problem seems to be the clutch coil but I will test it to cofirm.
Thanks everyone and I will post my findings so we all learn.
 

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It looks like your getting a large Current Draw thru you Switch. I figure you switch is rated for 10amps. I would look to see if you PTO clutch wiring is shorting against any metal or your PTO Clutch is Shorting out.
 

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Have you checked the output of the voltage regulator/ rectifier (if your engine has one). I have a 318 and the VR/R was putting out 17+ V. The VR/R output should be in 13.5 V to 14.5 V range. I also had a fried PTO, don't know which fried which though.

Good luck.
 

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unplug power to the pto, run the machine, does the switch and connections still get hot?? (unlikely btw) if they do then you likely have a direct wire
short to ground...

and no need to replace the whole wiring harnes, solder a staight pin to your multimeter probes, you can then peirce the wire insulation and test the wires as you move forward (without actually damaging the wire when you remove the pin!) All you are checking for is continunity, not voltage if you have a wire other than ground that when touched to ground closes a circuit you have found yor problem...

clearly there should be an inline fuse as a fuse failure is cheaper than a harness and switch replacement-

now having said that, sometimes in difficult cases you shunt the fuse and let a part burn to locate the problem, that is the situation you are in right now, unplug on item at a time until the problem stops.

a shorted PTO makes the most sense right now though-

and again unplug the PTO if the problem goes away you found your cause!

17-18 volts while high should not melt the parts like that, there is a more serious issue at hand... melted wires is a dead short (without a fuse, your wire, connecors and switch have become your fuse!)

After you fix the problem PLEASE install an inline fuse, it is just cheaper than switchs and power connectors :trink40:
 

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Isn't there a fuse to protect your wiring from this happing. Maybe the clutch is bad, can you adjust it? Try testing it first before melting any more wires, don`t worry about the name Scag. this should help you sort things out.

http://www.ganos.com/electricclutchtesting.pdf
I have a similar problem on my 1994 Bunton BBMH25 Zero Turn Hydro with a Kohler CH25 and an electric PTO. The PTO circuit blows my 20A fuse after a few minutes; the fuse doesn’t blow if the PTO is not engaged. I checked the wires from the relay feeding the PTO and they show signs of excessive heat, though I am not convinced they actually melted through the insulation.

Following your Scag link above, using an Ohm meter, I have about 4 ohms resistance across the PTO when it is cold. I checked the air gap to find it was very wide and narrowed it down to .020 at the three slots. It still blows the fuse.

I can't see what brand the PTO is with it mounted on the machine. I have already replaced a burnt-out ignition switch; both clutch and starter relays; removed, sanded, and reattached the battery ground to the frame; and now am going to replace the 16 ga wires feeding from the relay to the PTO with 14 ga since they seemed to be melted together in a couple of spots. I am concerned that the PTO is pulling too much amperage or shorting out completely once it warms up. Any suggestions?


The Bunton part number for the PTO is PL7384, which is a Texron part number good for Bunton and Bobcat ZTR’s. I don’t know for sure what brand of PTO it is, but I noticed a cross reference to a Warner 5210-44, and then a 5215-48 on another site, but have been unable to find it. The bore is 1”, has a single pulley, and the PTO is counterclockwise. I am having a very difficult time finding a replacement for a reasonable amount of money (so far, all listings over $500!).

Thanks for whatever advice you can give me.

Robert
 

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I have a similar problem on my 1994 Bunton BBMH25 Zero Turn Hydro with a Kohler CH25 and an electric PTO. The PTO circuit blows my 20A fuse after a few minutes; the fuse doesn’t blow if the PTO is not engaged. I checked the wires from the relay feeding the PTO and they show signs of excessive heat, though I am not convinced they actually melted through the insulation.

Following your Scag link above, using an Ohm meter, I have about 4 ohms resistance across the PTO when it is cold. I checked the air gap to find it was very wide and narrowed it down to .020 at the three slots. It still blows the fuse.

I can't see what brand the PTO is with it mounted on the machine. I have already replaced a burnt-out ignition switch; both clutch and starter relays; removed, sanded, and reattached the battery ground to the frame; and now am going to replace the 16 ga wires feeding from the relay to the PTO with 14 ga since they seemed to be melted together in a couple of spots. I am concerned that the PTO is pulling too much amperage or shorting out completely once it warms up. Any suggestions?


The Bunton part number for the PTO is PL7384, which is a Texron part number good for Bunton and Bobcat ZTR’s. I don’t know for sure what brand of PTO it is, but I noticed a cross reference to a Warner 5210-44, and then a 5215-48 on another site, but have been unable to find it. The bore is 1”, has a single pulley, and the PTO is counterclockwise. I am having a very difficult time finding a replacement for a reasonable amount of money (so far, all listings over $500!).

Thanks for whatever advice you can give me.

Robert
UPDATE:

I pulled the old one off. It is an Ogura PTO, and sure enough, when I slid it apart I could see that the epoxy bed that coats the windings had swollen to the point that a portion of the winding was rubbing against the moving parts. It must short out when warm.

So now...I need to replace it. The PTO is unusual in that it has a four-bolt mounting instead of the typical 3-bolt ones you see. The Ogura number is MA-GT-BU2, and I find lots of MA-GT's for Exmarks but not with my mounting plate. Does anyone know if one can buy a mounting plate adapter to install a 3-bolt clutch on a 4-bolt engine block pattern?

Robert
 
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