Thanks for the many responses. I installed a new PTO switch but it did not fix the problem. I took it to a local mechanic who works on JD mowers and he found out it was the clutch. If the battery does not maintain a charge of over 12 volts, the mower deck will not operate. He installed a new clutch and it fixed the problem. The only downside was the price of the clutch at a John Deere dealer which was over $300. But at least now I am back mowing. Just thought I would pass this on so that others can have the information.
If the charging system was not functioning correctly it would cause the PTO to cut out when the voltage dropped below a certain level. If the charging system is working properly, you should see the voltage (full throttle) somewhere between 13 and 14 volts. Water under the bridge now but that is what should have been checked first.
Not necessarily. If the rectifier was putting out 12.4 volts, it would be enough to keep the battery up but not enough to keep the PTO engaged (assuming electric). I only mention this because it was brought up in the original post. A PTO that doesn't stay engaged due to low volts/amps won't get fixed by replacing the PTO clutch.
Sorry that I am to late to help.
But, I had the same problem with my STX38.
My problem, was the connection between the clutch and the wiring harness.
It got packed with dirt, since the connection is located under the tractor frame.
I could not clean it enough to work, so I had to replace the connectors.
later
GNN
