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The blades on my Cub CADET 1515 (300 hours) quit turning last fall. I disengaged and engaged the PTO switch several times and could not get the blades to turn. So, I decided to wait until this spring to address the issue. When I try to start the mower this spring the engine would not start (the flywheel would turn about 60 degrees or less and return back to starting position). I thought I might have a compression issue or weak battery. The battery checked out good. I turned the flywheel a few times, turned the ignition and got the engine to start. But, the PTO would not engage the clutch. A few weeks later I had time to continue working on the issues. I tried starting the mower several times (even rotated flywheel several times but the mower would not start). So, I performed several electrical checks. 1st, checked the resistance on the clutch and it measured 4.6 ohms. I also check the continuity on PTO switch and found Com B and C to be good when both pulled out and pushed in. Com C provides power to PTO clutch. For Com A (starter inhibit circuit) with the PTO switch pushed in the continuity was 3. I assumed that Com A was failing, that's why the mower would not start. So I connected a wire across the A connector pins on the harness and got the engine to start. I tried to PTO switch and did hear a click, but didn't hear the pulley spinning (the mower deck was removed from the mower prior). I should looked to see if pulley was spinning but I didn't. So I checked the gap on the clutch and found the gap to be about .035 inches. Since I didn't have tools to remove the clutch and I didn't know what brand clutch was on the mower. So after research, I adjusted the the gap down to .020. I started the mower with the wire installed in the Com A connector pins on the harness and found the pulley was engaged even without pulling out the PTO switch. Does that mean the bearings in the pulley are bad? I rechecked the resistance on the clutch and it measured 9.5 ohms. The continuity was good. Also I reinstalled the PTO switch and got the mower to start along with the rotation of the pulley. I pulled the PTO in and out several times and could not stop the pulley Maybe Com A of the PTO switch is OK! Any ideas on how to resolve issues?

Try resetting the air gap to .013-.015". IF the pulley still turns then it is likely the pulley bearing. But you must pull the clutch assy and verify this.

Note: The IPL indicates two different PTO clutches so you need to get the OEM numbers off the clutch. Most likely it is a Warner clutch but could also be an Oruga which why I gave the Oruga setting.

Also the clutch resistance is out of spec as it should be closer 2.4-2.9 ohms. The high resistance you measured would cause a weak magnetic field and clutch would be slipping under load.

StarTech said:

Try resetting the air gap to .013-.015". IF the pulley still turns then it is likely the pulley bearing. But you must pull the clutch assy and verify this.

Note: The IPL indicates two different PTO clutches so you need to get the OEM numbers off the clutch. Most likely it is a Warner clutch but could also be an Oruga which why I gave the Oruga setting.

Also the clutch resistance is out of spec as it should be closer 2.4-2.9 ohms. The high resistance you measured would cause a weak magnetic field and clutch would be slipping under load.

Click to expand...

I decided to adjust the air gap on the PTO clutch back to .035 inches (original gap). I started the mower with the PTO switch installed and checked the pulley and it was not spinning. I pulled the PTO knob out and in several times and pulley was still not spinning in either case. A few hours later I started the mower again and the pulley is now spinning. I pulled the PTO knob out and in several times and the pulley was still spinning in both cases. I checked the voltage of the battery (13.89 volts) and the voltage of the clutch (14.05 volts) while engine was running. The resistance for the clutch was 5.9 ohms and clutch continuity was 0. I'm stumped.

Sounds like you have a broken wire that makes & breaks contacts randomly ,
This is going to be a right royal PIA to find .
Easiest way is the remove the deck & belt get the mower up in the air and very stable .
The start pulling /pushing wires , particularly where they plug into the clutch and at every joint & plug .

bertsmobile1 said:

Sounds like you have a broken wire that makes & breaks contacts randomly ,
This is going to be a right royal PIA to find .
Easiest way is the remove the deck & belt get the mower up in the air and very stable .
The start pulling /pushing wires , particularly where they plug into the clutch and at every joint & plug .

Click to expand...

I was thinking the same thing. But, the PTO switch has continuity of zero for Com C (power to clutch) when the PTO knob is pulled out and continuity of 1 when the PTO knob is pushed in, so COM C is working correctly I think! So in the first instance the lawn mower started, I pulled out the PTO knob but I could not get the pulley to spin -maybe the air gap in the clutch was too large (.035) or maybe a random break in a contact would make sense. But the second instance when the mower was started, the pulley started spinning immediately without pulling out the PTO knob, so how that happen? Is the PTO switch bad?

The PTO clutch is permanently connected to the power side of the battery and you turn it on & off by connecting it to ground.
So if you have a bad wire it can be making a ground contact thus completing the circuit
Way way back the clutches grounded via their body through the crank & engine but that was found to be unreliable so they started using 2 wires to the clutch
And again some use a relay to switch the + side & others just use the PTO switch to switch the - side
A common problem is the clutch wires breaking loose at the clutch which is why most of the new ones have a plug built into the clutch body
Another common problem is the wires fouling on the clutch or drive pulleys and chaffing through the insulation

Finally I have found time to work on my lawn mower PTO issue again. I did I acquired a better multimeter, one that beeps for continuity. Note: I did remove the mower deck prior to the following checks. First, I checked the battery voltage which was about 13.9 volts. That's good Next, I checked the continuity for the PTO switch. With the PTO switch closed, COM A beeped and with the PTO pulled open, COM B and COM C beeped. So far I think the PTO switch is good. Then I checked the continuity and resistance of the PTO clutch (I haven't removed the clutch yet, so I don't know the brand of the clutch). The continuity check beeped and resistance thru the PTO clutch was 2.7 ohms. So far I think the clutch is good. Next, I sat in the lawn mower seat and turned the ignition key until the lights came on. Then I pull out and pushed in the PTO switch and had clicking in both cases. So I think the PTO switch is still good and the Clutch may be good. Next I tried to start the mower with the PTO switch pulled out, but would not start. That's good. So then I pushed in the PTO clutch and started the mower on the third try. Here's where it gets a little fuzzy. After starting the mower, I checked to see if the pulley on the clutch was spinning or not. I may have been wrong, but I thought the pulley was not moving, so I pulled out out the PTO switch and it started spinning. After getting out of the seat, the lawn mower stopped running. That's Good. So then I started the lawn mower again and the pulley was spinning without pulling out the PTO switch. Then I pulled out and pushed in the PTO switch several times and the pulley keep spinning until I turned off the engine. I started the engine several more times with the pulley spinning. Upon inspecting the PTO clutch, I found two black wire coming out of the clutch, with no apparent damage. I also wiggled the wires while engine was running to see if I could get the clutch to stop, but had no success. With this information are there any suggestions on what to try next to solve this problem besides removing the clutch. Are there other wires that may be the culprit?

If your PTO pulley is spinning in the disengaged mode then the bearing in the pulley is probably bad. But it might the brake not working due to wear; therefore you check the air gap setting. I kinda doubt that this is the problem but worth checking. This brake is how the PTO stops the blades from turning quickly.