craftsman dyt problem - pto switch melted

anvilhead(Cape Cod)May 19, 2011

I have a problem with my 2005 Craftsman DYT4000.

The other day while I was mowing, the PTO switch got hot enough to partially melt near one of the terminals. I shut the engine off until I figured out where the odor/smoke was coming from, and after the thing cooled down the engine wouldn't restart. No clicking or anything - nothing at all. (I've had no battery trouble since I bought it, although it's five years old now) I pushed the machine inside and put a charger on the battery, and after an hour or so it cranked over and ran normally.

I bought a replacement PTO switch, installed it, and today after mowing without incident for 15 minutes the same thing happened again - the switch heated up and melted the push/pull knob. I did notice the ammeter was jumping around a lot prior to that happening.

I went to a local small engine repair shop (he doesn't service Craftsman products) and ran the scenario by the owner. He seemed to think the culprit might be the voltage regulator, although he said it could be an intermittent ground.

I've ordered a new regulator, and hopefully it will be in before the grass is up to the windowsills.

Has anyone here experienced a problem like this on their tractor?

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One would think that the load through the switch , possibly a ground or high clutch draw could be causing this. Many Sears tractors have a diode in the lower part of the harness to lessen voltage spikes to ground as well. Make a hot switch, I doubt if tho. 917 model #? Do you have a multimeter? Does your clutch have adjustment nuts? How many questions am I allowed?

    Bookmark   May 19, 2011 at 11:43PM
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anvilhead(Cape Cod)

Follow-up: Today I disconnected every electrical connector I could find, none showed no signs of corrosion or crud, some had light dust/grass clippings around the terminals, however the terminals were bright when separated. (FWIW, this machine is kept indoors except when mowing, and has never been used in wet conditions)

There are no visible signs of damage or abrasions to wiring from PTO switch and ignition switches to electric clutch.

What is the correct procedure for checking the electric clutch? I have a multimeter, but must confess I have very little experience using it, so step by step would certainly help.

tomplum - The machine is 917.275660, and I'm not sure what the adjustment nuts look like, if there are any, and you can ask unlimited questions, provided you have as many answers....8>)

    Bookmark   May 20, 2011 at 12:13PM
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    Bookmark   May 20, 2011 at 12:29PM
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anvilhead(Cape Cod)

justalurker - thank you for the PDF files. I ran an ohm test on my clutch, and it reads 0.6, far below what is considered a failure according to the troubleshooting guide.

It looks like clutch replacement time.

    Bookmark   May 21, 2011 at 10:38AM
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BEWARE! The electrical schematic for this tractor shows the PTO clutch has the "anti-spike diode".
An ohm reading of .6 would certainly indicate a shorted clutch coil.........IF...........the ohmmeter is connected with the correct polarity.
To determine for sure if you are reading the resistance of the coil, or if you might be reading the inverse resistance of the diode it is necessary to connect the ohmmeter leads in one direction and record the reading. Then you reverse the ohmmeter leads and test the circuit in the opposite polarity.
A good clutch featuring a diode would read the spec of 2.4 to 2.9 ohm in one direction, but would read zero (or near zero) ohm in the opposite direction.
If the clutch is shorted, your readings will be low ohm, in either polarity.
So, you might have a shorted clutch, or you might be reading the diode.

    Bookmark   May 21, 2011 at 11:20AM
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Important to check both directions to be sure but in my experience the diode in in the tractor harness NOT inside the clutch assembly.

The Warner docs are specific that the clutch be disconnected from the harness before checking.

    Bookmark   May 21, 2011 at 12:01PM
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anvilhead(Cape Cod)

mownie 7 and justalurker -

After reading your replies I did a retest with the clutch disconnected and free of the harness (as before). With the test probes connected I got a reading of 0.6, then I reversed them and had the same results, 0.6

This is relatively new territory to me - in simple terms does this low reading indicate there would be too much current passing through the PTO switch, resulting in the switch failing?

I (1) want be sure my test procedures are being done properly, and 2) replace only what is necessary.

Thank you for your insight.

    Bookmark   May 21, 2011 at 1:55PM
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As I expected because I've never seen the diode IN the clutch. Every diode I've seen is installed in the harness or on the tractor side of the connector.

0.6 ohms is very low (close to a short) and that would draw a lot of current through the switch.

With a shorted clutch the battery will be dumping as much current across the PTO switch as it can handle before it melts. In essence, your PTO switch is acting like a FUSE.

From the symptoms you posted and the clutch readings you posted, the clutch looks like the problem and now you might need a new PTO switch again. I'd also check the diode and load test the battery.

As always, free advice is worth what you paid for it.

    Bookmark   May 21, 2011 at 2:14PM
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anvilhead(Cape Cod)

Yes, the PTO switch will need replacing, but with the clutch apparently being the culprit at least it should be the last time.

I'll get busy tracking down a clutch, there seems to be a fair number of 180505 sources out there, however no dealer in my immediate area stocks them, and a PTO switch is already entroute.

Meanwhile, a neighbor has loaned me his tractor, so the
lawn no longer looks like wheatfield. :+)

    Bookmark   May 21, 2011 at 3:05PM
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Based on that the clutch assembly is depicted below encircled by a dotted line, the diode is a non-replaceable, integral item to the clutch assembly.
Plus the legend for removable/non-removable connections shows the diode connections to be "inboard" of the removable clutch connections (pigtain plug-in), I would say the diode is part of this clutch assembly.
This kinda hints at the fact that when testing any PTO clutch, it's a good idea to remember to reverse the ohmmeter leads and check twice.
Yes, I agree with JAL, this clutch is shorted, AND that you might already have a "stressed" PTO switch.

    Bookmark   May 21, 2011 at 3:37PM
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First clutch I've seen with the diode internal BUT since the schematic isn't showing the clutch connector I still reserve judgment till I see one in person and locate the diode.

Regardless of that, you are correct that the measurement should be taken in both directions to eliminate any question and Warner should amend their troubleshooting guide UNLESS no Warner electric clutch has an internal diode and the Sears tractors are using Ogura clutches or another brand.

    Bookmark   May 21, 2011 at 6:57PM
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I have always deplored the lack of information that OEMs include in technical literature, but it is about what one should expect from mass marketeers of products built for them by someone else.
I can't remember all the details, but it seems to me that we had a case maybe a couple of years back where a member here had a thread about his particular Craftsman tractor which DID have a separate diode that plugged into the PTO clutch harness, and was sold separately.......listed in the Sears IPL too. I believe that member was seeking to learn if he could maybe go to "radio shack" and buy a simple diode instead of the Sears sourced replacement part item.

    Bookmark   May 21, 2011 at 7:51PM
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An fyi , I've used both the Radio Shack 276-1143 3a diode or the Kohler 2575531s kit. The Kohler kit is a nice thing. It looks a bit beefier, has a cable that can replace the one going into the connector, some heat shrink for good repair.

    Bookmark   May 21, 2011 at 8:07PM
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I've replaced quite a few of those diodes on Sears stuff and always found them just on the tractor side of the clutch connector or a few inches back from the connector heat shrunk into the harness. A common diode stocked at the local electronics store. Sometimes zener diodes are used as rudimentary (crude and cheap) voltage regulators in simple charging systems.

I'll agree that the circuitry info most OPE OEMs include in their tech lit is more an electrical diagram and does not deserve to be called a SCHEMATIC.

JD does a much better job on their technical manuals and charges dearly for them. As usual... we get what we pay for.

    Bookmark   May 21, 2011 at 8:10PM
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anvilhead(Cape Cod)

mownie, justalurker, and tomplum, after reading the above posts re: diode -

I went out and looked at the leads on the tractor side of the connector, and in the red wire right just before the connector is a 2" length of heat shrink with an irregular shaped bulge beneath it, I presume that to be a diode.

Also, near the base of the connector a short length of silver wire crosses over from under the heat shrink to the terminal on the black wire.

(At first glance the heat shrink looks just like a repaired area, however I've had the tractor from Day 1, so that rules that out)

Hope this helps the discussion, or if nothing else I'm certainly learning something.....You guys are good.

    Bookmark   May 22, 2011 at 7:03PM
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Thanks for that info. It just shows to go you that I put to much faith in the dotted line enclosure being an indication of "integral diode".
I'll keep my eyes open a little wider from now on.

    Bookmark   May 22, 2011 at 7:25PM
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anvilhead(Cape Cod)

mownie, justalurker, tomplum -

An update here,

I ordered in a new Ogura clutch from an eBay seller in Atlanta and it arrived this morning. The old one came off easily and I was up and running in no time. I also had to do the PTO switch, which arrived earlier in the week. The new clutch read 3.3 ohms across the terminals, a far cry from 0.6

I mowed for three hours, no problems whatsoever, so thanks to you guys I saved a bunch of time and money and learned something while I was at it.

Your help is much appreciated. Watch for a check in the mail for the free advice. 8>)


    Bookmark   May 27, 2011 at 6:58PM
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What a difference some Ohms make...

Make sure you burnish the new clutch as it says in the Wagner lit... makes a big difference in the service life of the clutch.

    Bookmark   May 27, 2011 at 7:01PM
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