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  1. #1
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    John Deere LA140

    Default LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    Our LA140 has had its share of problems, but so far it has only taken time, money, and a few well-chosen curse words for me to correct them. This one has me stumped, though. The mower started making a high-pitched rattling sound when the mower was engaged that I couldn't pinpoint. After continuing on for about twenty minutes the engine died. After that I could get the engine started, but as soon as I engaged the PTO the engine would die again. When I had a chance I looked around online and read some forum postings about electrical issues, and decided to start with the PTO Clutch Switch. I took off the connector and ohm-ed it out and it appeared to be OK, but when I pulled the switch itself out and ohm-ed it out it was obviously bad. A closer look at the "C" terminals (the first line of three positioned at the top of the switch) showed some melting of the plastic around the lugs. I took off to the closest John Deere distributor, procured a replacement, popped it in, and pushed the connector back on, but after starting the engine the PTO would briefly engage but kill the engine. In trying to start the engine again I found that the 20A fuse had blown, too.

    I found where someone had provided a link to a technical manual for the LA100/110/120/130 from 2002 and so I printed out the wiring diagrams, wiring harness diagrams, and PTO/RIO troubleshooting pages for the LA130, hoping they would be close enough to my LA140. I noticed a couple of discrepancies but plowed on. I have an Electrical Engineering degree and have been an instrumentation and control engineer for an oil field services company. I've had to spend weeks going through equipment manuals loaded with wiring diagrams in order to tie an external control system in and didn't think that these five or six pages would present any problem but I was wrong. It didn't help that some of the diagrams were labelled incorrectly and that the diagnostic steps must have been written by an unpaid intern judging by all the mistakes and left out steps, but after an entire afternoon of checking I still hadn't found the problem.

    As I was calling it quits for the evening I climbed on the tractor to back it into the garage and started it. At a whim I put it into reverse (automatic) but kept the parking brake on, pushed the RIO button and held it, then engaged the PTO and the dang thing roared into life. I listened to it a bit, then let go of the RIO button and pushed the pedal barely over into forward, and the PTO remained engaged and the engine never sputtered. I switched the PTO in and out a couple of times to see if my luck would hold (because I really hadn't changed anything except the 20A fuse and unmating/remating some connections) but about the time I thought I'd go out and finish mowing the yard the PTO clutch disengaged of its own volition even though the engine kept an even note. I worked the PTO switch in and out a few times with no success at engaging the PTO clutch and the engine continued to run. I switched the ignition to OFF thinking I'd do some more checking, but when I discovered the PTO switch (S2) had the same two terminals fried, I decided I'd had enough for one day. I tried to crank the engine again, once more with the idea of backing it into the garage, and the starter made no noise. I found the 20A fuse also blown again.

    The wiring diagram I have (for the LA130, I've ordered the CDs which cover the LA140 and yet another PTO switch just minutes ago) shows that the 20A fuse would be inline between the battery (not the Stator/voltage regulator) and the ignition switch, and those wires go on to land on the same terminals of the PTO switch that had melted (two different times) and from there through a harness connector (X5/X6), on to the PTO clutch itself. From the PTO clutch there is a fairly straightforward path to ground and also a splice which handles the RIO or magneto cut out switches and relays. When I checked earlier with my ohm meter positive lead on the PTO switch connector looking through the PTO clutch with my negative lead on the negative post of the battery I read something like 33.6 ohms, which should only produce about 357mA when powered up. Not enough to burn a 20A fuse or melt the PTO switch, but there's obviously a large current coming from somewhere.

    Has anyone been down this road before, or maybe can throw an idea or two my way?

  2. #2
    Silver Member
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    Jun 2013
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    N. GA
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    LX188/445/755

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    Quote Originally Posted by Juan Deere View Post
    Has anyone been down this road before, or maybe can throw an idea or two my way?
    My 1st thought would be a bad PTO clutch. Is it a 2 wire connector? If so...
    With it disconnected how many ohms between the wires. Then ohm out both wires to case ground.
    Last edited by BBO; 06-23-2013 at 06:23 AM.

  3. #3
    Silver Member
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    Jul 2000
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    223
    Location
    Western,MA
    Tractor
    JD 850, L130, 317

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    PTO coil specs are 2.4 - 2.7 ohms across the terminals this is for a L130 but should be the same for yours. My coil is 3.8 ohms a little high but was working when the bearings went out.
    You said there was a squealing noise also, check the deck bearings and also the idlers, the last thing would be to check the PTO clutch bearings. Mine went out because of the bagger constantly turning the PTO off and on. There are replacemen bearings on ebay for relatively low cost. There is also a replacement clutch assembly for about one third what JD wants. I am going to order one for a spare.

  4. #4
    Veteran Member David_Kb7uns's Avatar
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    Willamette Valley Oregon
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    Kubota X 4

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    Also some of the electric PTO clutches need the airgap checked and adjusted, as they wear the gap gets bigger and current goes up.

    David Kb7uns
    Grand L3130GST LA723 Loader, ATI grapple, ATI grapple bucket, WR Long front remote, Kubota rear remotes, Bradco 408 Backhoe with thumb, 60"KK brush hog, 60" RM Finish Mower, Speeco Post Auger, 72" KK rear blade, 60" box blade
    BX2230 LA211, RCK60, GCK60 Bagger,42"Land Pride Tiller, XB BB, XB RB, rake, Fimco 3PT sprayer
    G2160 RCK60 Mower
    RTV1100 Orange, Work Lights, Front Rear Winch,Rear Screen, High Mount air cleaner, water seperator
    2010 Polaris RZR 800 S
    2007 CAN AM Outlander 800 LTD

  5. #5
    New Member
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    John Deere LA140

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    I must be having internet issues, too. I submitted a post earlier today thanking everyone for their replies, and my post isn't here.

    I do thank everyone who has added a post or sent me a private message offering advice. The more I test the more I scratch my head. The electric PTO clutch on the LA140 has its connector mounted directly to the front of the clutch, not on pigtails, so it's about impossible to put multimeter leads on. I had to back up to the next connection (X5 on the wiring diagram). Ohming between the pin for the yellow wire (501) and the black wire (110), which should have given me the resistance of the coil in the clutch I show 2.4 ohms, which is at the bottom end of spec. From yellow to battery ground is 0.5 ohms, and from black to battery ground was 2.4 ohms. They look like good numbers, but the problem is that the yellow wire comes straight from the PTO switch, so with the switch ON then there is pretty much a dead short from the battery to ground, which is what is melting the two terminals on the switch. The connector on the harness which mates to the one on the PTO clutch is keyed, or else I would swear that it must be reversed to put the yellow wire on the "upstream" side of the coil and the black stream on the coil's "downstream" side. I haven't taken the PTO clutch off and opened it up but I would be very surprised if there was any way for the polarity to get swapped inside.

    I had other weird readings, too, like resistances measured on the pins of connectors which would be the same for about three tries and then appreciably larger or smaller the next time I measured. I finally got to the stage where I opened every connector-to-connector and connector-to-switch/relay just to try and chase away some of the gremlins, and did point to point measurements to each end of the harnesses. We've had the tractor for nearly six years and, other than lots of bad idler and pulley bearings, it has worked well overall. Now it seems I'm chasing multiple electrical issues. I'm close to ordering another wiring harness on top of everything else even though I can't find anything physically wrong with it.

  6. #6
    Silver Member
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    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    Quote Originally Posted by Juan Deere View Post
    The mower started making a high-pitched rattling sound when the mower was engaged that I couldn't pinpoint. After continuing on for about twenty minutes the engine died. After that I could get the engine started, but as soon as I engaged the PTO the engine would die again.
    I would want to take the deck off or at least a belt to find the mechanical problem. I still suspect the clutch, but it sounds like you have more than one problem.
    If you are really inclined to see the current, get a DC ampmeter on the clutch wire and use some temp switch to engage the pto.

  7. #7
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    John Deere LA140

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    I forgot to add that yesterday I did check the current. I don't own a clamp on amp meter, unfortunately, but I made two jumpers that I could plug into the connector that the PTO switch mates to and then attached my multimeter inline with those to directly measure the current. I only checked through the two terminals that feed the PTO clutch directly, not the other two that RIO latch relay and the brake switch. I also swapped out the 20A fuse for a 30A one so that I could see just how high the current would go. The current was about 17A, but the battery voltage was only at 7.8V which calculates to a resistance of about 0.46 ohms and that closely matches the 0.5 ohms I measured. The battery is weak, anyway, and I had done a lot of testing before I got around to checking the voltage so I can see that the current could easily have been higher than 20A.

    The deck will come off this afternoon, along with the clutch. Once I get the clutch off I can lay eyeballs on it and also take some direct measurements to try to figure out what the hey.

  8. #8
    Super Member
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    Deere 110tlb, 4520, x749, L130

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    My thoughts on this would be to check out the deck for issues causing drag first, then check the clutch (most likely replace it) and use a new switch with a new clutch if you have to got that route. Often when the clutch craps out it damages the wiring shorting it to the frame somewhere so check for this also. My older L130 had similar problems and I quickly learned to engage/disengage the mower deck at an idle and as least frequently as possible. The replacement clutch is getting alot more hours of use this way.

  9. #9
    New Member
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    John Deere LA140

    Default Re: LA140 w/intermittent PTO, melted PTO Clutch Switch and blown 20A fuse

    Yesterday didn't go as planned so I am just now getting back to the tractor.

    I took off the clutch and it is as many of you suspected. The bearings are a complete mess, with the outer seal completely gone and the ring (with the cups in it that keep the ball bearings neatly spaced) is peeled back. Since it was still engaging and turning the mower blades when I started working on it, the clutch bearing must have been on its last gasp and heating up the clutch assembly rapidly, which in turn must have melted the insulation on the electromagnet windings inside. Measuring resistance on the two pin connector directly mounted to the clutch, I still get 2.4 ohms across them, as per spec. But when I measure from each pin to the clutch case I get 2.4 ohms on one side and about .4 ohms on the other side, but unfortunately the 0.4 ohms reading is also on the "hot" wire side (the yellow wire from the PTO clutch switch), shorting the positive side of the battery (via the 20A fuse and the PTO clutch switch) to chassis ground. Had it been the downstream side of the magnet windings where the insulation melted and shorted, electrically the clutch would have probably continued to work just fine. As it is, the clutch is both electrically and mechanically shot, so I'll be ordering a new one.

    I may still have some gremlins in the harnesses but hopefully replacing the switch and clutch will chase most, if not all, of them out. If not then I guess ordering a new wiring harness is in my near future.

    Thank all of you for the suggestions.

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