Well, after fixing the charging system situation on my riding mower I got halfway through cutting the grass when the PTO just started cutting in and out.  At first I thought it was the charging system again or perhaps the battery getting weak again so I stopped cutting grass and threw the battery on the charger.  The next afternoon I went out to cut the rest of the grass and noticed that the PTO was cutting in and out again after about 5 minutes.  I pulled the mower into the garage where I checked for voltage to the leads heading down to the PTO.  Battery voltage was present (13.6V) with the tractor running and the PTO switch turned on but the PTO was not engaging and spinning the blades.  🙁    If I let the tractor sit overnight the PTO would engage when turned on, which leads me to believe that it would operate just long enough until it got hot enough to quit.    Time for a new PTO clutch!

Replacement PTO Clutch

After searching the owners manual for the replacement part number and searching online with Amazon and eBay, I finally found a replacement electric PTO ranging anywhere from $200 to $350.  It was not exactly the kind of money I wanted to spend on this old tractor considering a new one with similar features would run around $1000 to $1200.  When searching for ways to rebuild or even adjust the PTO in some tractor forum, I came across a reference to Pete’s Small Engine which had a replacement PTO for $150 and with reasonable shipping.  I am happy to say that the tractor finally seems to be fixed and I was able to cut the entire lawn without one incidence of the PTO cutting out.  I hope that I am able to get at least one more season out of this old riding mower.

My Troy-Bilt Bronco riding lawn mower quit cutting the other day because the electric PTO would not engage.  I checked the leads going down to the crackshaft mounted electric PTO for power with a test light.  It had power running through leads when the PTO knob was engaged.  I then began looking online for a replacement PTO which ranged anywhere from $250 to $300 on eBay and Amazon.  I did some more research online about PTO not engaging and found another user who had similar issue with the electric PTO not engaging.  His issue was a low battery charge which did not allow the electric PTO enough juice to engage.  Evidently the PTO runs entirely off the battery power and when you have a low battery charge the electric PTO will not engage or stay engaged in my case.

This got me to thinking to check the charging system on my mower.  I went to start the mower from the shed to bring it into the garage and it would not start.  🙁  A quick charge of the battery and the mower started and while I was driving it up to the garage I tried the PTO which engaged too.  🙂  I set my multimeter to read DC voltage and put the black lead on the negative battery post and the red lead on the positive battery post which read 12.6V with the engine NOT running and 12.6V with it running.  This meant the charging system was not working.

I checked the two wires which connect up to the voltage regulator mounted on the starter.  I set the multimeter to check AC voltage and put the leads on these two wires coming from the stator in the engine.  It should be about 28VAC when operating normally.  Mine showed 0VAC and that was when I noticed one of the black wires was cut.

After removing the engine shrouds and covers to get a better look at the damaged wires I noticed that the other one was nearly cut in half too by rubbing up against the engine flywheel.  A couple of weatherproof butt connections and I was able to repair the leads coming from the stator.  I reassembled the engine covers, etc to retest the charging system and now I had 30VAC from the stator leads coming into the voltage regulator.  I also had 14VDC from the third middle wire on the voltage regulator.  The charging system was now working and I was able to finish mowing the other half of the yard!  I was just happy I didn’t need to purchase an expensive PTO or STATOR and it was a simple fix.