New to me, used Sears GT6000 - electric PTO issue

[QueBota]

Took my son to a baseball tournament over the weekend, found this for sale on the way home.

Seemed like a nice enough garden tractor, 44" deck (3 blades), 18hp B&S IC, 3 forward, 1 reverse, Hi/Low range, good tires. Started right up, sounds OK, mowed some grass for a test drive, tranny sounds OK, looks used but not abused, not cleaned up or pressure washed, not bad for a circa 1994 tractor, $350.00.

I have been buying old/used $200.00 riding mowers for the "lawn" around the house. The B2910 leaves ruts in the grass, wife doesn't like that. My current old/used riding mower is just about used up. The stamped steel front axle beam is cracking at the mount and the bushing mounts for the axles are becoming bigger than the bushings. Can't complain, this one has given me lots of service and doesn't owe me anything. The 17.5 hp B&S still runs like a top, the rest of the mower is falling apart around it.

Can't bring myself to buy a new HD/Lowes riding mower and didn't want another used lawn tractor, I was looking for something with a stronger front end (cast with grease fittings).

Brought it home, checked it over, changed the oil, gassed it up and started to mow. The fellow down the road from me abandoned his house. He used it as an ATM one too many times and couldn't afford the payments so he just walked away. I have been cutting his place since he left, he has about 2 acres of lawn which he used to cut with a Exmark Zero Turn.

I mowed for a while and everything seemed good, engine ran fine, mower deck pretty smooth, steers and stops, pto engages and disengages, all forward and reverse gears work. Feeling pretty good about my purchase.

Let my son mow for a bit while I supervised. All of a sudden the tractor began to vibrate like crazy, couldn't tell what was going on. I ran over and saw that the deck drive belt had broken but the amount of vibration/shaking made no sense.

We limped back over to our place to take a look. The bolt that retains the PTO clutch on the end of the crank had backed out and was finger tight. When the deck drive belt went it took out the wiring to the clutch, the loose fit of the pto on the end of the crank was causing some serious shaking.

I feel like a dumba$$ now but I never thought to check that bolt, normally I need a 2 foot ratchet to remove them. I think it may have been loose and when the belt came off, the tension of the belt holding the pto was released and that allowed the pto to slide down the shaft free from the anti-rotation tab and the vibration/shaking may have loosened the retaining bolt even more.

Need to pick up a new deck drive belt this afternoon. Hope the pto clutch didn't get killed by all the vibration. I am left with a cut wire (between the connector and the pto) with no good way of telling which way to reconnect the wires. They are both the same color and look like someone cut them with scissors (the ex-drive belt cut it pretty cleanly).

What is the best way to determine which wires to connect? Don't want to damage the clutch, have priced them out at between $200 and $300. I am afraid the unit may have been damage in the adventure but don't want to foul it up anymore.

This is my first experience with the electric PTO setup. All my other mowers worked by tensioning the deck drive belt as you lowered the deck. From what I have read the pto functions like the clutch on the front of an auto AC compressor. When power is applied to the pto is causes the unit to couple and drive the belt to the deck.

Any thoughts or suggestions on the pto or tractor in general would be appreciated.

Thanks,
Dave

 

[jinman]

I think your PTO electromagnet will not care which way it is connected. It should work fine either way. To be on the safe side, check the resistance of each wire to ground to make sure there is no short. You should be able to read the coil resistance wire-to-wire and infinite resistance to the frame of the mower. There is a remote possibility that there is a diode to dump the large inductive spike when the clutch is disengaged, but my guess is this would be obvious by changing polarity of the meter while measuring resistance. If it measures lower resistance in one direction than the other, this could indicate a diode. In that case, polarity is important based on the polarity of the diode. If you don't see any difference in resistance with the polarity reversed, I'd just wire it and go for it.

 

[QueBota]

Thanks for the advice. Don't know why they don't color code the wires from the connector to the PTO. The wires that run from the harness down to the connector (where you would separate to install a new PTO) are color coded and the plug is configured to only join one way. I believe there are two black wires and one red wire on the harness(battery) side of the plug and two wires of the same color from the other side of the plug leading to the PTO.

Normally when wires come apart, especially on something that has been assembled for a while, you can tell which way the wires were oriented. Not in this case, I have looked at it a few times and placed them together and one way looks as right as the other.

My plan was to bare the ends, hook up some jumper wires and give it a quick shot of 12v DC and see if clutch pulls up against the hub (I am assuming that it would draw it up), hopefully I will hear a nice strong "click".

I seem to remember DC being particular regarding + and -, some DC motors will run backwards if you reverse the polarity, don't know if it would have the same effect with a magnetic clutch.

I told my neighbor the story after lunch and he expressed concern about the balance (or lack thereof) and the vibration on the end of the crankshaft, he thought that it might have been hard on the engine. Nice guy, but he always gives me something else to think/worry about.

Thanks again,
Dave

 

[jinman]

My plan was to bare the ends, hook up some jumper wires and give it a quick shot of 12v DC and see if clutch pulls up against the hub (I am assuming that it would draw it up), hopefully I will hear a nice strong "click".

I seem to remember DC being particular regarding + and -, some DC motors will run backwards if you reverse the polarity, don't know if it would have the same effect with a magnetic clutch.

Dave, do you have an ohmmeter? Before hooking up 12 VDC any way to that clutch, you need to check that the clutch coil is not shorted to ground and that the coil is not open. The best way to do that is with a VOM set to a low resistance scale. Put the black meter lead on one wire and the red on the other and watch the meter. You should get some low resistance. Remove one lead and touch it to the engine block. You should get infinite resistance. Now, attach the leads to the clutch wires again and read the resistance. Swap the red and black leads to see if you get the same resistance. If it is the same, then hook up the 12 VDC to see if the clutch works.

An electromagnet clutch is not the same as a motor. It is just a magnet and all you are doing with changing the positive and negative wires is changing North and South polarity of the magnet. In a permanent magnet motor, that will cause it to rotate in reverse, but your clutch is just producing magnetism to draw in the clutch plate which is a non-polarized piece of metal. That's why I said the electromagnet does not care about polarity.

When any coil of wire has current going through it, it builds up a magnetic field. At the instant you disconnect the power (switch to OFF), the magnetic field collapses. This collapse induces a high reverse polarity spike to the coils of the magnet. It is of such high voltage that it will arc across a switch or in some cases cause internal arcing inside the electromagnet coil itself. That problem can be cured by placing an electronic device across the coil that will conduct the current and inhibit the electrical arc. Some devices work in only one polarity and others work for either polarity. If you measure the DC resistance on the clutch coil and it reads the same when you swap leads, you have nothing to worry about. If there is a big difference, then your polarity is important and needs to be wired carefully. My guess is that you will read the same for both polarities and will be good to go no matter what way you connect the wires, but I would never do it without checking first.

BTW: I have a John Deere with an electric clutch. If you would like, I can check it and tell you what I find, but there will be no guarantee yours is the same. I don't have a schematic of my clutch, but I can look to see how it is wired if you'd like.

 

[QueBota]

Jim,

Thanks for your time, appreciate the advice.

I picked up a generic Advanced Auto deck drive belt on the way home, actually 2, 78 x 1/2 and 79 x 1/2, off course the specs in the manual list belt #131264 as 78-1/2 x 1/2.

Didn't have time to mess with tractor last night, wife, 3 kids, animals and misc chores got in the way.

I have a fairly good digital multimeter, will do the tests when I get home this evening after it cools down a bit, supposed to be low 90's today with a low 70's dew point. I don't enjoy that at all, I am a cold weather guy.

I will try to post the results this evening or early tomorrow AM.

Looked at the wires again last night. Turns out I was mistaken but the results are the same. Someone had done some creative wiring under there and it was a little confusing when I first looked at it. The wires that were "cut" must have been from a previous project that was partially removed.

The wires that feed the PTO were completely ripped from the connector at the PTO side, didn't leave one strand behind, both the same color, still can't tell which wire came from which terminal. Now I get to tin the end of the wires and try to solder them back in the connector without melting the plastic.

Hopefully this will work out, as I looked over the GT6000 again last evening it seems to be a pretty solidly built little tractor, much beefier than the disposable lawn tractors I have been using. May have to try to find a front snow blower for it to use in place of plowing with the back blade on the B2910.

Thanks,
Dave

 

[jinman]

Well, my John Deere electric clutch has a resistance of 3.5 ohms. That means it draws about 4 amps when the mower is running and charging the battery at about 13-14 volts. I checked both polarities on the clutch and it read exactly the same in both directions, so there is no electronic device on the coil. My clutch has an integral connector built into the case. The wires coming to the plug are white and black with black being ground. White goes to the PTO ON/OFF switch. The plug is keyed so it can connect only one way. That's the way JD does it on the LA145.

 

[QueBota]

Jim,

Broke out the multimeter and did some testing, it was still warm and very humid at 20:30, didn't feel like messing with it a whole bunch, I had so much sweat running down my arms and hands it was difficult to handle the wires and connector. Going to wipe down the wires and connector with some degreaser this evening to make them easier to handle.

Easy test first. Good strong 12.4V DC at the pto switch end of the plug with ignition on and pto switch set to engage.

Tested resistance of pto clutch, red to A, black to B 2.7 ohm. Red to B, black to A 2.6 ohm. I couldn't locate the alligator clip ends for my test leads so I had to hold the wires to the end of the probes with my fingers, hard to do when your fingers are sweaty and a little greasy. I repeated the test and the results were the same. Don't know if my sweaty greasy fingers changed the readings much.

I found some Warner electric pto troubleshooting document on the web that indicated that the resistance should be between 2.4 and 2.9 at 70 degrees F. My ambient temp was around 88 degrees F so I think I am pretty good regarding resistance.

Didn't do the amp draw test, have to dig out my electrical kit with the jumper wires and clips. I was pretty worn out last evening, didn't feel like locating that toolbox. Know it is in the shop but not sure exactly where, need to get cleaned up and organized a bit. I hate when it takes longer to find the tools than it does to do the job.

Tried to do the pto leads to ground as you indicated but was getting some strange unrepeatable results, will try again this evening.

I studied the connector again where the wires were ripped out buy the former drive belt and was almost able to tell which wire went to which terminal buy the traces of insulation and wire strands left behind. Not 100% certain but pretty close. I stripped the pto leads back a bit and temporarily pushed them into the pto to harness connector. Ignition on, pto switch engaged, nice sharp click from the clutch. Pto switch disengage, pto clutch releases. I guess that is a good thing.

For what it is worth there is one red wire (+) and two black(-) wires on the harness side of the connector. The two black wires are joined on one terminal. The connector is keyed but the wires on the pto side of the connector are both black, same gauge, no other markings I could see.

Need to install the deck belt this evening and reinstall the pto clutch so the little anti-rotation tab on the tractor is located in the slot on the pto clutch. Then I need to figure out a way to get the pto leads back in their connector. It looks like the terminals are crush fit on one end with blades on the other and either aluminum or steel so tinning and soldering might not work out. Doesn't appear to be any way to remove the terminals from the plastic connector without damaging the connector. I might perform an "operation" and dremmel the connector open, reattach the wires then insert it in the harness side of the connector. The harness side of the connector is female and completely surrounds the pto side, that should hold the connector together. I don't want to splice into the harness side of the wiring. If I get a new clutch it will come with a new lead and connector.

Will update this evening or tomorrow, rained overnight, feels like a rainforest out there this AM, when I retire I want to head for a semi-arid climate, the humidity around here really bugs me. I would rather be up to my knees in snow at 10 F then deal with dewpoints between 70 and 80, current temp 78.4 and cloudy, dewpoint 73.

Thanks,
Dave

 

[QueBota]

Update my own thread.

Got the deck belt installed, takes about one minute, pretty good for ease of installation but I could see where the belt could come off just as easily.

Did a quick an dirty wire job on the pto just to see what works. It locks and turns the blades but it appears to pull the ammeter into negative territory. Not sure how accurate the meter is but I can't imagine I should be running off the battery when the pto is engaged.

Going to try to do an amp draw test on the clutch sometime today. Specs I have state the clutch should draw at least 4 amps. Also going to try to check the air gap, specs indicate a pretty wide range, IIRC something like .005 to .025, with gap set to .012 if setting the adjustment.

Other than that it cuts pretty well and seems to run OK. Need to replace the fuel line from tank to filter and try to level the deck a little. Had to snug down the valve cover on the drivers side, it was dripping oil, managed to do it without removing the muffler.

Thanks,
Dave

 

[jinman]

Dave, it sounds like you are gettin' there step-by-step and making a fine mower out of one that needed some TLC. I would guess about 4 amps for your PTO clutch too and I don't know why the ammeter would show a negative draw. That does seem a bit strange. Does the ammeter sit exactly at zero when the tractor is off?

 

[QueBota]

It sits a little to the left of zero, but not much. It appears to charge just fine when running at WOT, maybe two increments right of center, at idle, it sits right at center. When I engage the pto there is a noticeable drag on the engine and the ammeter goes to between 1 and two increments left of center. The ammeter may be a little biased towards the negative side. If I engage the pto with the ignition on, engine off the ammeter moves to about 2 increments left of center.

If the weather cooperates I am going to go out this afternoon and check out the amp draw and battery volts, we have been having thunderstorms and showers for the past day or so and the dew point is in the low to mid 70's. This isn't a show stopper for me right now so I will do what I can when I feel like messing with.

The tractor is actually a 1993 model and is in what I would consider average shape for its age. The frame is pretty thick, the front end is cast with greaseable fittings, 23" wheels in the back and 16" wheels in the front, seems to be well built.

Thanks,
Dave