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Southern Nevada desert | The easy thing to do first is switch the MFWD valve coil with the PTO valve coil, sometimes the coil will short internally but take a few seconds to heat up and short circuit causing the computer to turn off the power. The tone ring drops on the shaft and is held tight by the bearing pressed up against it.
Here are some tests from an earlier post
Is the pto light flashing?
If it is a code will be set.
To check for codes move a fuse to the "diag" position, work the turn signal to get "CCU" in the display, pull the turn signal towards you (flash to pass position) to enter the CCU, use the turn signal to find address 1 and read the codes.
The FWD, diff lock, and PTO all use the same coil. These can get hot and fail, test by switching with another coil.
A bad pto speed sensor will cause the computer to disengage the pto.
The PTO solenoid is on top of the PTO housing above the PTO shaft.
Put a spare fuse in the "Diag" location (2nd horizontal fuse, top row), use turn signal left/right to select CCU on tach, pull turn signal toward you (flash to pass) to enter ccu, select address #01 in the upper box, codes will be displayed in the lower box.
072 rear pto circuit failed
073 rear solenoid/circuit failed
075 rear pto speed too low with pto on
To test the sensor/sensor circuit:
Select address 4
first digit 0, not used
second digit engine speed sensor
third digit pto speed sensor, should consistently change 0-1-0-1-0-1 as pto is turned by hand, no change or erratic signals indicates a sensor or wiring problem.
To test the switch/switch circuit:
Select address 9
first digit 0, not used
second digit rear pto "on" switch, should consistently change from 0 to 1 when the pto switch is turned on
third digit rear pto "off" switch, should consistently change from 1 to 0 when the pto switch is turned on. second and third digits must never be the same, they must be 010 or 001, if both switches are on or off at the same time for more than 2 seconds pto will be stopped.
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JD 7810 pto trouble
