Sounds like a short in the wire leading to the pto, try disconecting the wire from the pto and test again, trace the wire back and make sure the insulation has not rubbed through where it passes through the frame.

Can you post a link to the wiring diagram for that model?

I did some further testing. I disconnected the 2 wire pig tail from the pto, sat in the seat and started the motor. The engine ran normal until I engaged the PTO, then the engine died.

I also put an Ohm meter on the PTO side of the pig tail. I got full scale right deflection both times...ie.. I switched the meter wires on the pig tail and got full scale deflection both times.

Did the fuse blow with the clutch disconnected? I would really need to see the schematic/wiring diagram to go further. Testing something like a relay or clutch coil with a ohmmeter is not going to show much, they are very low ohms and will almost always deflect a analog meter full scale. At 12v if the clutch draws 8 amps it only has 1.5 ohm resistance, pretty hard to measure even with a digital meter.

Found a diagram here:
http://www.managemylife.com/mmh/owner_manuals/24562/CRAFTSMAN-Lawn,-Tractor-L0522687?brand_name_search=917274641+CRAFTSMAN

About the only thing besides a shorted PTO clutch that would blow the fuse and kill the motor is if the red wire between the clutch and pto switch is shorted. You could 'test' the pto by connecting the black wire to ground and using a wire with a 10 amp fuse connect to the terminal for the red wire and tap the + battery terminal, if it clicks and does NOT blow the fuse it would have to be a short in the red wire from the pto switch to the chassis ground or another ground wire in the wiring loom.

I would post the diagram but can't grab a copy from that website.

try this link for the diagram, its the only I can find. Pg 33

Here is a link that might be useful: electrical diagram

Same diagram, you can see the electric clutch about half way down, so IF the fuse did not blow with it disconected AND the engine keeps running it has to be either a short in the red wire to the pto switch or a bad clutch (or that diode shown) the diode is there to prevent a voltage spike when the pto switch opens which would eventualy destroy the contacts in the pto switch.

So does it run normaly with the clutch disconnected? If so then you should do the fuse test I mentioned earlier, if it's a two terminal connector disconnect completly, ground the terminal to the black wire to the chassis, connect a wire with in-line fuse to the terminal with the red wire, the clutch should 'click' as the driven plate contacts the drive side. You may be able to observe the plate move a small distance ~1/16" as the wire is connected. If the test fuse does not blow then you know the clutch works, if it blows the fuse then the clutch or diode are shorted and need to be replaced (diode= --->:----)

when you say connect a wire with in-line fuse to the "terminal" with the red wire, please explain a little further.

It's still not clear when you disconected the clutch, started the engine you say the engine died when you operated the pto switch. Did the fuse still blow?

yes, the fuse blowes, even with the pto pig tail disconnected, with the engine running and I pull the pto switch, the engine will die unless I immeditely push the switch back in.

Well it's begining to look as though there is no problem with the clutch itself. So it sounds as if their is a short someplace either the pto switch or the wire from the switch to the clutch is shorting out.

Pull the connector off the pto switch and use your ohm meter (one lead to a good ground) to check the red wire that goes to the clutch with the pigtails disconected at the clutch. That should read open, if it is not open that wire is shorted someplace. If that reads good i.e. no resistance then test the pto switch terminal that the red wire connects to, if that reads a short to ground when the switch is operated then the short is internal to the switch and you will need a new pto switch. PS-all this done with the key off or main fuse pulled.

I put the gnd on the batter neg, tested the red wire at the connecting block behind the pto switch, got full scale right deflection "0" Ohms on the meter.

testing the switch: with the switch pulled out (pto actuated) I get no movement at all on the meter.

I'm assuming the switch is bad?

Nope that indicates the red wire is shorted somewhere to the chassis ground, that's good news for you bad news for the parts people, probably the easy fix it to just cut the wire near the switch and re-rout a new wire of the same size to the clutch, cut both ends and use a crimp connector to join the new wire from switch to clutch, may want to get a length of wire loom stuff (split plastic tube stuff) to protect the new wire from damage.

Cool hook up a new wire and let us know how it works. You just saved a ton of money by not replacing the switch and clutch which so far seem to be good. Just FYI from other posts here seems the clutch should read 2.5 to 4 ohms so if you can read that on your meter or borrow or buy a cheap digital meter you may want to check that too.

Just make sure that the wires to the clutch are connected correctly, with that diode across the clutch reversing them will present a dead short also. If you can see the diode the 'bar' (:) end should be connected to the red wire and the arrow (So Switch--- Red---:

the conector block behind the pto switch, there are two red. One is paired with a blue wire to the same connector on the block and the other is by itself, on the next terminal. Not sure exactly which red wire to cut. any ideas?

Can you post a picture of the "block" and wires you are referring to? But according to the diagram, the single red wire would be the one to cut.
The red wire that is paired with a blue wire is the "hot wire" going into the PTO switch. The blue wire you found would be power to the fuel solenoid and/or hour meter depending on your options package.

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got pix, just having trouble copying here, progress in work

mownie,

Could you post how to include pictures in a post, I for one tried following the 'instructions' link and got a 404 page error trying to find out how.

Just in case anyone is wondering....
1. Create a Photo-Bucket account: www.photobucket.com
2. Upload photos you want, into your photobucket account (try not to upload these big 10 megapixel pictures you have - rescale them to a manageable size like 800x600, or 640x480)
3. View your photos in photobucket; you'll notice 3 boxes beneath each photo... labelled: URL link, HTML tag, and IMG Code.
4. Pick the middle one (HTML Tag) box, and highlight (single click) the little text string inside the box, that has the text string: "href=http:\\....." etc. Make sure you copy the entire string, including the "a" and the "less-than" sign before it.
5. Press "CTRL-C" on your keyboard (copies the text into your computer's memory)
6. Start a new message on this forum, and put the cursor where you want your photo to be placed (in relation to the text you just wrote).
7. Press "CTRL-V" on your keyboard (pastes the link you copied before)
8. When you preview the message, you should see the photo

you're done....

Here is a link that might be useful: Just in case it might work this time

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WOW! the famous deck hanger and cracked frame pictures. OK wheely you got to post the monkey picture also.

here'a couple pix showing the single red wire, and the red wire with the blue wire also

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So you think its the single red wire I need to cut and replace?

Yes the single red one, you did measure a short to ground from that one last week right?

I tested again, with the neg. test lead to the battery neg. term. and the red test lead to the red wire and got full scale right deflection on the ohm meter. (I'm guessing this means no resistance and this is indeed where the short is, the pto pig tail was unplug also during this test)

crissymustang:
The plug you are holding in your hand......does it plug onto the back of the ignition key switch or to the back of the PTO switch?
If the plug you hold in your hand connects to the ignition key switch (and that's what it looks like to me).........DO NOT CUT ANY OF THOSE WIRES!!!!!
You have not found the correct connector yet.
And if you have been doing the tests for a short on the wrong connector, you probably have erroneous test results.
The red wire you have been told to check for a short is the red wire that LEAVES the PTO switch and runs to the PTO clutch assembly.
Stop and answer my questions before you cut any wires. I'm not getting a warm and fuzzy feeling about this right now.

yes, the connector in the pix is the backside of the PTO switch, I haven't touched the ignition wires. I even took out the PTO switch once, because it was easier to test the switch that way, but yes its the PTO connector.

Refer to pictures below.
I had to make sure of which connector this was in your pictures.
Yes, the single red wire is the one to cut. Be sure you don't cut it too close to the plug or you will not be able to splice your new wire to the old wire stub.
Down at the PTO clutch end of this operation you will encounter the 2 wire connector that joins the PTO clutch to the chassis wire harness. You will want to cut the red wire of the CHASSIS side of harness connector. Follow the same technique of leaving at least 2" of wire still in the connector to allow you to splice in the new wire.
Sorry if I raised some unwarranted concerns about the ID of the connector block. Better safe than sorry.

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well, not the red wire. I spliced in a new red wire, re-connected the PTO switch, and the clutch harness, started the motor ran normal, until I engaged the PTO, then the engine died. I checked the 20A fuse, its blown. Back to square one.

Ideas?

Dead shorted PTO coil? I think I mentioned waaay back testing it with a 15A fuse and eliminating everything else. But you did say the ohms were something like 2.5 0r 3 when tested, still could have a short to ground their someplace.

I didnt test the pto coil. I have the test wire, but not clear on the testing procedures, little foggy there for me.

Do I hook up a black neg test lead from pto terminal to chasis gnd and then my red test lead from positive battery to pto red terminal?

Yes that would be the way to do it, but please use a inline fuse so IF it is a dead short you don' incinerate the wire, your hand or anything else. Also connect the + wire and make the ground connection to test, not good making sparks around a battery.

okay, when I connected the neg line from the pto to gnd, and the red (with in line 15a fuse) to + on the battery, the blades started to turn, and ran like it should with the pto engaged.

So that says the pto clutch/coil is 'good' (not shorted) and things work when you bypass the pto switch. Now if you connect that same wire to the pto switch and if it blows the fuse??? Still 'could' be a partialy cooked clutch drawing too many amps but it does not sound like it.

This is strange and odd as their is nothing else in the safety switch system that is going to blow the fuse.

Can you test both ends of the wire you cut and see if there is some short there? It's begining to sound like something rubbed on the frame, overheated somewhere in the wire harness and melted insulation allowing some wires to contact each other.

Hopefully mownie will show up to unravel the mystery, I am stumped and I have been doing this for 45+ years. But without having hands on it's a guess.

My son was mowing at the time, and he said he moving the ignition switch and the pto switch at the same time when this all occurred.

Humm, sounds like one of the switches took a hit being both operated at once, may be time to take the meter to both and check them out to see if the contacts that are supposed to open/close do so in the proper order.

My head is turning in circles!!!
Chris, could you please post a couple of pics showing your "slice & splice" of the new wire to the old at the PTO switch connector block and at the 2 wire connector down at the clutch chassis harness??
There must be some detail we are all missing somehow.
The symptoms are just not consistent at all points in the timeline of testing done so far.
I'm taking some aspirin and then I'm gonna mow the yard.

Mownie,

I feel your pain, it seemed that the problem was down to a short between the chassis and that dang red wire! I am wondering if it has melted the insulation and compromised another wire in the wiring harness to ground, ugg nasty stuff but sometimes you just have to take off the wire loom and look for that stuff. Had it happen in an old Datsun where a parking light shorted out and cooked the insulation burning three or four other wires under the hood.

found the problem, running just fine now. Thank you gentlemen.

Here's the story. Well, mownie wanted pix of the slices, so I grabbed the camera and headed out. I started to pull the wires to a visible point for the shoot. I also had some rubber insulation over an older splice from last yr when I replaced pto clutch. I decided to shoot pix of all the splice. I began to remove the rubber insulation from the original spice, going from the red wire to the connector (chasis side) for the pto. As I was cutting away the rubber insulation, I saw a single strand hard wire from my splice going into the neg side of the 2 wire connector. I have no idea how, when, or why this happened. Why has it been running fine for months, then all of sudden start causing a short? How did it get there? I would swear it was sabotage if I didn't know better. I guess it was a good idea to go back to the beginning and check the splices. I was convinced it was the switch and even put in a new one this morning, maybe I can get my $20 back on the switch.
Anyway, thank you gentlemen, sorry for puzzle, but it ended up being a 2 min fix once I found the short.
thanks again, much appreciation

Great News,

Almost proves I am not insane, well almost...

Yup odd things happen, sometimes a little strand gets out of place and wiggles in at a later date, happens to us all, had the Directv guy here years ago hooking up a second receiver and he was having fits till he cut off the connector he had just attached and crimped a new one on, don't know bout you but after I reached 40 years my eyes started to go and I need bright light and a magnifyer to see those things anymore.

Anyway happy you got it solved, probably could have saved running an extra wire but at least it's working.

My head still hurts :^)

Mownie,

throbbing like this?

http://www.youtube.com/watch?v=Y5zIw-LdTXY

I am helping my neighbor with his Craftsman 917. He has two melted PTO switchs and grass that is growing. I see two discorlored terminals on the PTO Connector when I unplug the PTO Switch. Both are red which is the wire that entergizes the switch. Is cleaning or replacing the connector inside the plug the answer if I can remove it fron the plug? Ater replacing the PTO switch the last time it worked for 30 minutes and then melted before his eyes.
Thanks

Well, you are sorta/kinda trying to do the right thing (posting model number) but 917. is only the beginning of the model number. After 917. there should be an additional string of numbers that actually identify the specific model.
Hopefully, once we know the true model number, a wiring diagram can be found.
I can tell you this much already:
It's possible that the main fuse has been replaced with a bigger capacity fuse (higher amp rated), and THAT might have been done because the correct fuse was blowing repeatedly (because of the condition you found......burnt, dark terminals).
It is also highly likely that the PTO clutch may be drawing too much current which is aggravating the other defect you have found.
It is advised that the PTO clutch be tested for air gap and amp draw and resistance.
I have a PDF manual I can e-mail you covering the tests on the clutch. If you want the clutch manual send me an e-mail.