PTO Electrical Clutch Problem

[KE4AVB]

Cub Cadet 17AE2ACG010 2008 with Kohler Courage engine.

Now I have already figure this one out. It is first time I ran a PTO doing this.

Customer brings a Cub Cadet ZTR complaining of PTO that would not engage after mowing 30 minutes. I was able duplicate the problem twice. Just wondering what you guys would try to find the problem as this mower has already been in three shops.

[bluemower]

one likely failure occurs with the packard 56 female terminals. The loop tab applies pressure against a male spade to provide a solid connection. The loop will sometimes break and the result is an intermittent connection. This sometimes occurs on an older machine that has wet grass accumulated around the terminal. The loop corrodes and breaks. These connectors are inserted in plastic housings and breaks can be difficult to see. Testing with lamps and meters usually indicate the connection has power.

this is a very good question.

[KE4AVB]

Yes that normally happens but it not the problem with this PTO.

And I do replace several F56 female terminal every years. Matter of fact I buy them in lots of 100 (16-14 gauge). I even got two open barrel crimpers for these F56 terminals. One is modified to do the male terminals. I would have rather to just got a couple spare dies but the crimper manufacture doesn't sell them separately. Anyway the machine shop made the requested mods for me.

I made up a test interconnect cable so I could use my meter while mowing. That is how I was able to pin point the problem.

Back latter today I hope as I got to go to the fuel depot, money order store, HFT, and grocery stores.

[bgsengine]

In addition to bluemower's point, similar issues have been found with most any connectors, and internal contacts in the PTO switch, Key switch, relays and grounds.. Intermittent issues that only show up after extended run times can be tough to diagnose, especially if they problem suddenly goes away while trying to diagnose.. the question becomes "What just happened that fixed it" that can only be found by further testing.. I have also had PTO clutch winding failures that happen in the same way as ignition coils do - broken internal wires that lose continuity once thermal expansion has separated the broken ends enough.. Then there was the one "red herring" that was simply caused by the owner unhooking the ROM ground wire and it intermittently would bounce in between the linkage and frame and make contact only at a certain forward speed of the hydro pedal..and then jam there until vibrations or cooling let the wire hang loose again... Then there was the one that had a new engine put in that did not have sufficient charging system to keep the battery voltage up... when voltage dropped too low, worn electric clutch would stop working.. and driving it back to the shed and letting it cool down, was just enough re-charge to start up the tractor again for another bit of run time... (new upgraded charging system installed to the engine fixed that) ..

[KE4AVB]

Yes normally all those are common to look for problems.

A little more info. Before startup with PTO cool the resistance is 3 ohms then when it fails the resistance goes up to 4.5 ohms so it not an open circuit. Voltage at my interconnect is 12.9 vdc before and during the failure. Without looking at the clutch you can hear it clunking as normal. So you would normally think it is operating. By the way I shouldn't had try feeling the clutch as I scorched my finger tips.

The reason I made the interconnect test harness was because this mower is so low to the ground plus there was hot muffler involved. I also didn't want to stick my hand up between the PTO belt with the engine running and the fact I wanted live data from circuit before I got off the mower.

[38racing]

Does the PTO disengage while mowing or fail to reengage after 30 minutes.

[KE4AVB]

Never disengages by itself.

It actually disengages and re-engages fairly normally as long you are mowing. This particular mower has full reverse auto PTO shutdown and re-engages as you start forward so I was making sure I used that mode while mowing.

It is when you stop mowing for 30 secs or more that when it fails to re-engage. And it will not re-engage until the mower sits a little while with the engine off.

[38racing]

So after mowing for 30 minutes , then shutting off , and after 30 seconds off it won't restart? If like just 10 seconds off will it restart?

[KE4AVB]

Yes.

Don't you like these little brain teasers? Boy never had one to do this before so I will remember this problem for a while.

It is actually the clutch itself that is the problem so I have just ordered a new Xtreme clutch to replace due to the customer need of quick return; otherwise I would have tried the OX clutch as they are a little cheaper.

What happening is that there just enough magnetic field to partially engage the clutch disc but not enough to fully pull it off the brake. Non adjustable clutch so I can't reduce the clearance between the disc and rotor. With the increase in resistance and reduce current there simply not enough torque from what disc to rotor contact to break free of the magnetic brake once the clutch assy gets hot.

The clutch looks like a Warner but I need to pull it later today to find which OEM it is.

[KE4AVB]

Final failure analysis.

The clutch was a pain to get off. I got to design a puller for these as I have found one that will work yet. I just wish Cub Cadet would use anti-seize compound when they install these clutches and engine drive pulleys as I know very well that the drive is also seized. The clutch did turn out to be a Warner.

First the coil was out of spec per Warner troubleshooting info.

If meter reads below 2.40 ohms or above 2.90 ohms, then the clutch has failed and needs to be replaced.

The coil was starting out at 3.0 ohms and increasing to 4.0 ohms. I strike the below resistance reading as it was unrelated to the current problem besides I have seen published that the reading a can be as low 1.7 ohms and the coil still be good.

There was a second problem which was wear. The magnetic brake pads were half worn though, Also the armature (engagement disc) was worn in both the brake contact area and rotor contact area. All this greatly increased the air gap between armature and the rotor. This along with the lower current caused by the increase resistance make it impossible for the magnetic field to pull the armature into contact with the rotor.

This was my first truly worn out PTO clutch and not just a bearing failure. I think if it wasn't for all the wear the clutch probably would still be working.