My John Deere 7220 PTO problem. It is malfunctioning. The PTO engages at first when the switch is actuated, but after 15-20 seconds the PTO shaft speed too low warning light comes on and the shaft stops rotating. I can hear the PTO engaging inside the transmission when the switch is pulled. The PTO speed on the tachometer will not register any speed at all, even when turning. The 540 or 1000 speed light does not illuminate in the indicator light bank while the rear PTO connected light does.
I have tried to diagnose the problem from various angles. First I thought it was the switch in the cockpit. The input voltage was 12V, but the voltage at the modulator valve in the rear of the tractor was only 9V. Okay, I put in a new switch, but there is no change in voltage or PTO. Does the shaft sensor that appears to have failed have the potential to shut off the PTO if it doesn’t see the shaft turning?
The information on the dash says that the PTO speed is too low and the switch needs to be turned off and on again. There is no change in effect, the PTO engages for 15-20 seconds and stops again. I have not played with is the muductor valve that uses an electric (switch) solenoid to engage. My worst fear is that it’s the clutch packs, but I think the PTO keeps turning when no load is applied. My next guess is the shaft speed sensor.
Any insight would be appreciated.
I have had 3 different late-model tractors with electrical power take-off problems, very aggravating:
- Check the RPM sensor for the PIO, you have to watch the RPM to stay connected.
- The same goes for the speed sensor. Check if the wire harness has been unplugged. If not, try a speed sensor. I once had a call on a 6310 that engaged the PTO but would rotate slowly for several seconds and then shut down. I found a small piece of o-ring stuck in the hole in the modulator valve housing.