Weekend Freedom Machines banner

318 not playing nice...

2852 Views 30 Replies 8 Participants Last post by  Richards
My 318 has been fantastic since I used Jim B's suggestion and used Carquest's plug wire set. I have had 0 problems until today. I mow 2.5-3 acres and today I have blown 3 of the 20amp fuses. Replace it and good for another half acre or so.
It's running fantastic, but blowing the fuses. Any thoughts on where to begin when done mowing?

Terry B
1 - 20 of 31 Posts
Somewhere you have a wire grounding when the tractor twists just so. Look at the wires where they can rub the frame. These can be hard to find.
Good Luck ;-)

The 20 amp fuse is what supplies the power to the PTO, among other things. If your PTO has its coil potting compound or insulation breaking down internally, the coil might be shorted or partially shorted. Measure the resistance of the coil on the PTO -- it should be in the range of 3.5 to 4.7 ohms, give or take. If it is very much less, it could be the culprit in blowing the fuses...

There are other places in the wiring harness that often get shorted to ground, like the seat safety switch, but it receives its power through the 3 amp fuse. The headlights however are powered from the 20 amp fuse...but if the light switch is off, that wiring should not be a factor, regardless of its condition.

Did the fuse ever blow when the PTO was not engaged?

The fuse has only blown when mowing, at least so far. After typing the initial message, I went back out, replaced the 20amp fuse for the 3rd time, but this time the engine would not turn over. The panel lights are now working, but it will not crank. I decided to check the smaller fuse, and promptly dropped it. Currently have the belly screen off, but still haven't found that little sucker. Since I don't have any spares, I guess it's off to the store.
Really wishing I had followed through on buying that multimeter though!
I appreciate the input guys. I'll check into the bare wires.

Chuck, please explain...coil potting on the PTO???? I'm not sure what you mean.

Terry B
A part of the PTO is a coil that is under the pulley section, that has a compound (coil potting) to insulate it. Usually the older coils have one wire coming from it, and the case is grounded to the engine to complete the circuit. If that coil is out of tolerance, as Chuck stated, it could be shorting to ground and taking the fuse with it.
Use a multi-meter and check from that wire to ground, through the coil to see if the coil is within the 3.5-4.7 ohms.
Hope this helps,

Richard, in sunny, hot and humid eastern NC!
OK, sorry. Had to leave for a while. I still need to get a multimeter to give me readings. I currently only have an electric test meter that reads whole numbers. It is giving me a reading of 2.
Are you saying that if the reading is not in the specified range that it is just out of adjustment, or defective and needs to be replaced?

Most likely needs to be replaced, if your reading is a 2. That's way low. Your local JD dealer can order one, but I don't know if they come as a complete clutch, or if you can get just the coil. They are pricey, and your dealer is mighty proud of them.

Sounds like the coil is developing an internal short and drawing too much current which blows the fuse. If you have an Ogura clutch the coil can be bought separately, it was about $90 for the one on my 317 last time I looked. If the clutch is a Warner then you have to buy the entire clutch, $180 was the best price I could find for one for my neighbors Cub 1529.
Having just done the PTO coil thing I feel qualified to comment. Yes the PTO coil can and does degrade over time. Mine stopped working at a resistance close to 0! The new PTO coil resistance is 4.5ish. Mine also blew fuses so much so that previous owners hardwired the fuse boxes (still trying to fit that). You will need a good (digital) multimeter to check the PTO resistance and as Richard said less then 3.5ish is bad.

I replace the entire assembly on one 318 $350.00 (taking no chances) and just the coil ($170.00) on another 318. Wiser now I would never replace the entire assembly again, it seems to me the only part that can short out is the coil. So if your resistance is bad just get the coil, it's easy to replace. Just remember what the gap was before you replace and reset to that.

Good Luck.

jim s
Well, I stopped in at local Deere dealer today. According to parts dept, my type of PTO clutch is NLA. Mine was the older type(entire clutch) but must now be replaced with the newer style(coil & clutch sold separately). Unfortunately with everything else going on right now, the $393 + tax they quoted is not in my near future to make the mower deck spin.
Different question, though...would the bad PTO coil have anything at all to do with not cranking? I can't even get it to turn over now.
I have a 318 and it was doing something similar. The PTO would shut off after about a half hour of mowing. I found that the resistance was low and the coil was going bad. I used it a few time in this condition until one day the tractor just quit as if it was shut off. It would not crank at all. After about a week of checking it ended up being the key switch. I changed the switch and that got the tractor running but I still had to replace the PTO coil.
Well, I finally got a multimeter and I consistently get 1.4 ohms.
Are these PTO clutch/coils available other than through JD dealers? Are other tractors using the same?
The refusal to start issue was a bad ignition switch. At least it will run now. What are potential damages, if any, to not replacing the PTO clutch whether using the mowing deck or not?

Terry B

If you don't use the deck, just unplug the PTO and be sure that the blue wire is insulated against touching ground. Your PTO is nearly a dead short and using it could burn out wiring, take out fuses and breakers, regulator, or in other words, do a lot of expensive damage!
When possible, bite the bullet and buy a new clutch and PTO. Your electrical system will thank you, and so will your wallet.


Richard is correct, running that PTO with such a low resistance (and therefore such a high current drain...) will damage things. The high current draw likely contributed to your ignition switch failure, and can easily do so again.

If you are really handy, you can try your skill at winding your own replacement coil for the PTO -- it is rather involved but well described in the FAQ thread here:

If you are lucky and have the right Ogura clutch, check with Deere for a replacement coil. The coil for my 317 costs about $100.
I appreciate the input guys. I really don't think my level of either patience or expertise would make it wise for me to try the rewind. Unfortunately, I think Richard's "bite the bullet" is what will eventually happen. It won't be anytime soon though. The dealer has given me a quote of right at $400 since the older style that I have is NLA so I will need to get both parts.
Oh well, at least the mowing season is pretty much over here in Central N. Carolina.
When you do "bite the bullet", be sure to order the wiring adaptor for the clutch. It was about $17.00, and since the old coil had one wire and was grounded by the bolts to the block, the new coil has two wires, power and ground, and needs the adaptor, unless you are handy at wiring, then do it yourself.
What do you mean the mowing season is over? I'm still mowing every three days over here near the coast!

1 - 20 of 31 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.