Kubota BX1880, BX2380, BX2680 OPC System Check

BX1880 / BX2380 / BX2680 Owner Service Guide

The operator presence control (OPC) system stops the engine if the operator leaves the seat while the PTO is engaged or the speed control pedal is out of neutral. A switch under the seat tells the OPC timer whether the seat is occupied. When the seat empties with either control engaged, the timer shuts the engine off after about one second. Kubota calls for checking the system every 50 hours. The check takes about five minutes and needs no tools or parts.

How the OPC system works

With the key on and the operator seated, the seat switch is closed and supplies current to the OPC timer. The timer keeps the engine stop solenoid timer relay energized, and the engine runs. When the operator stands up, the seat switch opens and the timer holds its output for about one second. If the PTO clutch lever is OFF and the speed control pedal is in neutral during that second, the PTO and HST neutral switches keep the relay energized and the engine keeps running. If either control is engaged, the relay drops out, the engine stop solenoid moves the injection pump rack to no-fuel, and the engine stops.

The test engages one control at a time with the engine running, then has the operator stand up. The engine must stop within about one second each time.

Preparation

1. Sit in the operator's seat.
2. Set the parking brake and turn the key to OFF.
3. Move the range gear shift lever to neutral [N]. With the range lever in neutral the tractor will not move when the speed control pedal is pressed.
4. Take your foot off the speed control pedal so it returns to neutral.
5. Move the PTO clutch lever forward to OFF.

Test 1: seat switch and speed control pedal

1. Start the engine.
2. Press the speed control pedal and hold it down.
3. Stand up. Do not get off the tractor.
4. The engine must stop after approximately one second.
5. Sit down, release the pedal, and turn the key to OFF.

Test 2: seat switch and PTO clutch lever

1. With the range lever in neutral and the pedal in neutral, start the engine.
2. Pull the PTO clutch lever rearward to ON.
3. Stand up. Do not get off the tractor.
4. The engine must stop after approximately one second.
5. Sit down, return the PTO clutch lever to OFF, and turn the key to OFF.

When both tests pass, the check is complete. The engine start system check uses the same PTO and pedal switches and is on the same 50-hour interval, so the two are normally done together.

Failed test

If the engine keeps running after the operator stands up with a control engaged, the stop circuit is not being opened. There is no owner adjustment for this condition. Kubota's instruction is to stop using the tractor and contact the dealer. The causes, in the order they are normally checked:

Engine stops while seated, or will not start

The OPC circuit can also fail the other way. If the engine dies while the operator is seated, or the starter will not crank with everything in neutral, check the following in order.

1. Seat switch not closing. The seat must be fully down on the switch plunger. A worn seat spring or a loose seat can let the plunger release over bumps. Seat switch spring K2871-55550.
2. OPC fuses. There are two 5 A OPC fuses (OPC 1st and OPC 2nd) and a 15 A stop solenoid fuse in the fuse box. Fuse positions vary by serial number; the label on the fuse box cover identifies them. 5 A mini fuse T1065-30430, 15 A mini fuse T1060-30450. See Fuse replacement.
3. OPC relay, OPC timer, stop solenoid timer relay and stop solenoid.

Seat switch and OPC timer testing

Seat switch

The seat switch and seat turnover switch are under the operator's seat. Disconnect the two-pin connectors and remove the switch. Measure resistance across the two terminals. With the plunger released, the reading must be infinity. With the plunger pushed in, the reading must be 0 Ω. Any other reading indicates a failed switch.

OPC timer

The OPC timer is under the upper panel. Remove it and test it on the bench with a 12 V battery and a test bulb.

1. Connect jumpers from the battery positive terminal to the orange/white terminal and to the yellow terminal (yellow/red on some serial numbers).
2. Connect jumpers from the battery negative terminal to the black terminal and to one side of the bulb.
3. Connect a jumper from the red terminal (yellow on some serial numbers) to the other side of the bulb.
4. Disconnect the jumper from the orange/white terminal. If the bulb lights, the timer is good.

Parts

No parts are required for the check. These are the parts in the OPC circuit.

Parts catalogs: BX1880, BX2380, BX2680.

Related

• Engine start system check
• Fuse replacement
• BX Owner Service Guide

To have the test or the repair done at Messick's, schedule service.