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Hello,
I have a 61" 5100 with the CAT diesel and the PTO will randomly shut off while I am mowing. It is not consistent - sometimes it will happen once, I will shut off the switch, and it will start right back up, and I can finish the job. Other times it will happen repeatedly - cuts out, shut off switch, go for a little while and repeat. All the fluids are fine, and it is running fine otherwise. Anyone have a suggestion before I get a trailer and turn it over to a professional? Thanks for your input.

By hand check all PTO wiring making sure everything is tight & secure. Also check PTO switch connection at wiring harness.

If you are installing a new PTO clutch, follow instructions that come with new clutch or the above site.

Sounds like PTO going bad. Mine would shut off and after cooling would work for a while. Had to replace it and has worked fine since.

Check the battery voltage engine off , engine on & engine on with PTO on .
off should be around 12,5V , on should get to around 13 V after a minute of two , PTO on should be a little lower but higher than the off voltage.

Thank you for your responses.

I'm really hoping to not have to replace the PTO. The job looks pretty straight forward, but that is a lot of money just for the part.

I checked the connection at the switch. Wile it looks like there used to be a clip on the wire harness that broke off, the connection was firm. It was a little dirty, so I cleaned the contacts and decided to just replace the switch. The contacts at the PTO were OK, but I tightened the a quarter turn. The resistance of the PTO was about 2.6 ohms.

Based on the meter the voltages are 11.8 when not running, 13.8 when running, and 12.9 with the blades engaged.

It has been too wet to mow for the past 5 days and rain in the forecast for another 5. I'll have to wait a while to see if the new switch did anything.

Fingers crossed.

Thanks again for the help - I need all I can get.

Based on those numbers your battery is gone
If you continue to use it you will do damage to the starter motor and probably the alternator as well so start with a new battery .
All solenoids ( the pto clutch is just a solenoid ) have a fairly specific cut off voltage after which they just shut off.
Heavy load ones like the PTO often also have a thermal overload to shut off when they get to hot before the solder melts
Random shut downs are often the results of these devices working as they should to protect the clutch.

Thanks for the suggestion. I replaced the battery a year ago, and had it on a maintainer in the off-season, but you never know.

I had a chance to go out yesterday - ran great for the first couple of hours, then the PTO cut out sporadically for the 45 minutes it took to finish the first part of my lawn. I drove to the other part of the property with the PTO off, and it ran fine for the 45 minutes it took to do that.

Next stop - auto store for a battery check.

Thanks again - battery would be cheaper than a replacement PTO, and a lot easier to put in.

**Just back from the auto store - battery is fine. The search continues.

Then either the charging system is not up to snuff or the PTO is pulling too many amps
I use a clamp meter to check current draw
A good PTO should draw around 3 to 5 Amps depending upon which model it is
Some have air gap adjusters so check yours
The bigger the gap the further the solenoid has to push the plates the more current it will draw

Then there is the usual
Clean the battery cable ends, particularly the ground strap both ends
I like to paint over with liquid electrical tape

Can be as simple as a bad Packard (Delpi) (F56) wire terminal on the PTO switch.

Bad terminal on the old switch and the new one, too? Or are we talking about the wiring harness side?

I am going have to search out an ammeter, but the air gap seems to be 0.02" instead of 0.015". Since I had the battery checked, I already cleaned and firmly reattached the cable ends. I cannot for the life of me trace back where the ground attaches to the frame, however.

I referring to the wire terminal in the harness connector housing.

ENELSON - is the shutting off "load dependent"? Because I am having a similar issue with IS4500z with Cat engine. Mine occurs when I load the engine/hydraulics hard. Like going straight up a hill and the engine and hydraulics load and start to wine a little. Or if I do a very hard turn with one stick forward and one stick back. As time goes on and engine has run for a while so everything is nice and hot back there, it happens more and more.

For me it isn't the clutch itself - clutch is new within the last year with very little hours on it. Resistance tests at 2.6 ohms; with battery hooked up to voltmeter, battery is 14.2 v with clutch/blade on and it doesn't drop below this appreciably when the cut-out occurs. Air gap is properly adjusted. With the voltmeter on the wiring harness at the clutch, it drops voltage immediately when whatever is causing the cut out occurs...meaning that the feed to the clutch is dropping out (as though the switch is failing). I bypassed the switch and it still occurs.

The circuit is obviously very complex with various feedback loops triggering a clutch cut out but they all seem to be unrelated to engine load. They are more like temperature sensors, etc. Somewhere in one of those loops or relays I'm assuming something is tripping.

Next try may be to bypass those temporarily with a straight bridge from switch to clutch to start ruling out pieces of the puzzle.

Anyone have any other thoughts?

Happened to me once on a IS5100Z. In my case it was nothing other than getting to hot. Screen behind the seat was plugged up. Cleaned it, let it idle for a few minutes and away i went.