My 4310 wasn’t as responsive as I would like so I wanted to test the drive pedal potentiometers for adjustment and calibration. I would have to push the pedals half to three quarter inch before the tractor would start to move and it didn’t have a linear feel to it.
The service manual called for the use of a JDG1575 Test Kit which is just a breakout box for the wiring to the potentiometers. I couldn’t locate one and didn’t want to back probe the wires on my tractor so I decided to build a breakout harness. This can also be used to adjust the throttle potentiometer.
Materials and tools needed:
1 – 3 pin Weatherpack connector set
3 – 18-22 ga. T-taps
3 – 18-22 gauge male quick disconnects
1 – 4” 18ga blue wire
1 – 4” 18ga yellow wire
1 – 4” 18ga black wire
1 – Delphi Packard type crimper
1 – wire stripper
1 – Digital volt meter
To adjust the pots you also need a ¼” drive 8mm or 5/16’ socket on a ¼” drive pull handle and a 8mm or 5/16” wrench to hold the nuts.
Assuming you have the tools the total parts should cost less than $10.
I assembled the wires as they were colored on the tractor harness. The black is common/ground, the Yellow is 5V, and the Blue is the variable out to the control unit. A correct crimp will fold the terminal tabs over into the wire. I had to trim a little off the strain relief tabs to get them to roll over and crimp correctly. You push the seals on and strip the wires, then crimp the terminals. Make sure and assemble the male and female ends so the harness will plug onto the tractor harness and potentiometer in the right direction. Install the t-taps so they will point outward when the harness is on the tractor. Push the un-crimped male disconnects onto the t-taps. The wire opening on those is a perfect fit for the pointed meter probes.
To test you put the tractor in neutral and set the parking brake. Connect the breakout harness inline with one of the pots and turn the key on. I had to trim some insulation back on the quick disconnect terminals for my probes to connect. Input voltage should be measured between the black and yellow wires. The TOT/BOT voltage will be measured between the black and blue wires. Your black/negative probe will remain plugged into the black wire while testing and adjusting.
Input Voltage. . . . . . . . . . . . . . . . . . . . . . . . 5.0 ± 0.2 volts
TOT Position Signal Voltage1 . . . . . . . . . . 0.6 - 0.8 volts
TOT Position Signal Voltage2 . . . . . . . . . . 0.4 - 0.8 volts
BOT Position Signal Voltage . . . . . . . . . . . 3.6 - 4.5 volts
1. Early Models S/N - H120712, - H131963, - H141271
2. Late Models S/N H120713 -, H131964 -, H141272 –
My tractor was supposed to read .4 to .8 volts at the top of it’s travel and 3.6 to 4.5 volts at the bottom. My reverse potentiometer was right in the middle of specs and my forward pot was a little on the low side. I went ahead and adjusted both forward and reverse pots to .780V at top which put them around 4.2V fully depressed. The tractor has a much more positive feel to it. I could probably fudge the numbers up some but I don’t want it to start traveling with the pedals at rest.