Kohler 20RES troubleshooting: 8 fault codes and 40 symptom-cause-remedy entries from the manufacturer's own service documentation.
Kohler 20RES — full specs, parts & maintenance.
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| Accy PwrOver Warning | Accy PwrOver Warning — controller internal circuit protection activated | Controller internal circuit protection activated | Press OFF to reset; Contact an authorized Kohler distributor/dealer for service |
| MainPwrOverL Shutdown | MainPwrOverL Shutdown — controller internal circuit protection activated | Controller internal circuit protection activated | Press OFF to reset; Contact an authorized Kohler distributor/dealer for service |
| Accy PwrOver Warning | Accy PwrOver Warning — controller internal circuit protection activated | Press OFF to reset; Contact an authorized Kohler distributor/dealer for service | |
| MainPwrOverL Shutdown | MainPwrOverL Shutdown — controller internal circuit protection activated | Press OFF to reset; Contact an authorized Kohler distributor/dealer for service | |
| Emerg Stop Shutdwn | Emerg Stop Shutdwn | Remote emergency stop button activated or shutdown (prime mover) switch turned to the off (open, O) position | Reset the remote emergency stop switch(es) and reset the controller by pressing the OFF/RESET button; Press I on the shutdown switch to allow the engine to start and run |
| Accy PwrOver Warning | Accy PwrOver Warning | Controller internal circuit protection activated | Press OFF to reset; Contact an authorized Kohler distributor/dealer for service |
| MainPwrOverL Shutdown | MainPwrOverL Shutdown | Controller internal circuit protection activated | Press OFF to reset; Contact an authorized Kohler distributor/dealer for service |
| LossOfComm2 | Communication Lost with Secondary Controller |
| Symptom | Cause | Remedy |
|---|---|---|
| Controller display backlight is off | Backlight turns off after about 1 minute with no activity | Backlight will turn on when a button is pressed or the generator set starts |
| Controller display is off | Low or no battery voltage | Check connections; Check generator set battery |
| The generator set does not crank | Battery weak or dead | Recharge or replace the battery |
| The generator set does not crank | Battery connections reversed or poor | Check the connections |
| The generator set does not crank | Fault shutdown | Check the controller display for fault messages. See Section 2.5. Correct the fault condition and reset the controller |
| The generator set does not crank | Generator set in the OFF mode | Press the RUN button to start the engine or press AUTO to allow remote starting |
| The generator set does not crank | Generator thermostat tripped | For trips other than temperature (nuisance trips), reset the thermostat. See Section 5.5 |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Air cleaner clogged | Clean and/or replace the air cleaner |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Battery weak or dead | Recharge or replace the battery |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Battery connection poor | Clean and tighten the battery connections |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Spark plug wire connection loose | Check the spark plug wires |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Low oil pressure shutdown | Check for oil leaks. Check the oil level and add oil if necessary |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Fuel pressure insufficient | Check the fuel supply and valves |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Engine malfunction | Contact an authorized Kohler distributor/dealer |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically | Generator thermostat tripped | Check for obstructed air inlets and outlets. Reset the thermostat. See Section 5.5 |
| No AC output | Line circuit breaker in the OFF position | Place the circuit breaker in the ON position |
| No AC output | Line circuit breaker tripping because of overload | Reduce the load on the generator set |
| No AC output | Line circuit breaker tripping because of short circuit | Contact an authorized Kohler distributor/dealer for service |
| No AC output | Auxiliary winding circuit breaker tripped | Reset the circuit breaker (located in controller's service access area). Contact an authorized Kohler distributor/dealer for service if breaker trips repeatedly |
| Low output or excessive drop in voltage | Generator set overloaded | Reduce the load by turning off non-critical appliances or equipment. Use a load management system to power lower priority loads when critical equipment is not running |
| Generator set stops suddenly | Low oil pressure shutdown | Check for oil leaks. Check the oil level and add oil if necessary |
| Generator set stops suddenly | Out of fuel | Check fuel supply |
| Generator set stops suddenly | Overcrank shutdown | Reset the controller. If the overcrank fault occurs again, contact an authorized Kohler distributor/dealer |
| Generator set stops suddenly | Auxiliary winding circuit breaker tripped | Reset the circuit breaker (located in controller's service access area). Contact an authorized Kohler distributor/dealer for service if breaker trips repeatedly |
| Generator set stops suddenly | Fault shutdown | Check the controller display for fault messages. See Section 2.5. Correct the fault condition and reset the controller |
| Generator set stops suddenly | Generator set in the OFF mode | Press the RUN button to start the engine or press AUTO to allow remote starting |
| Generator set stops suddenly | Generator thermostat tripped | Check for obstructed air inlets and outlets. Reset the thermostat. See Section 5.5 |
| Generator set stops suddenly | Remote stop command received from a remote switch, ATS, or OnCue Plus | Check the remote switch position. Check OnCue Plus |
| Generator set stops suddenly | Engine malfunction | Contact an authorized Kohler distributor/dealer |
| Generator will shut down and the controller will display a fault (underspeed, underfrequency, or undervoltage) | Thermostat detects excess heat inside the enclosure | Reset the thermostat: disconnect utility power; open enclosure roof; remove air intake end panel; disconnect battery negative lead first; press thermostat reset button; reconnect battery negative lead last; replace air intake panel and service door; reconnect utility power; reset the fault on the RDC2 controller |
| Battery short circuits | Disconnect the battery before generator set installation or maintenance. Remove all jewelry before servicing the equipment. Use tools with insulated handles. Remove the negative (--) lead first when disconnecting the battery. Reconnect the negative (--) lead last when reconnecting the battery. | |
| Bodily injury and/or equipment damage | Battery short circuits | Disconnect the battery before generator set installation or maintenance. Remove all jewelry before servicing the equipment. Use tools with insulated handles. Remove the negative (--) lead first when disconnecting the battery. Reconnect the negative (--) lead last when reconnecting the battery. Never connect the negative (--) battery cable to the positive (+) connection terminal of the starter solenoid. Do not test the battery condition by shorting the terminals together. |
| Generator set stops suddenly | No fuel | Check fuel valves and fuel supply |
| Generator set stops suddenly | Model 20RESC/20RESCL only: enclosure thermostat tripped | Check enclosure thermostat and reset if tripped. See Section 5.5. Check and clear air inlets and exhaust outlets |
| Generator will shut down and the controller will display a fault (underspeed, underfrequency, or undervoltage) | Thermostat detects excess heat inside the enclosure; blocked air inlets and exhaust outlets | Check for blocked air inlets and exhaust outlets; reset the thermostat |
| Overcrank fault | Generator set does not start in three crank attempts (three crank cycles, 15 seconds crank and 15 seconds off) | |
| The generator set does not crank | Emergency stop switch or engine shutdown switch activated | Verify that it is safe to start the engine and apply load; Then reset the stop switch or engine shutdown switch |
| Generator set stops suddenly | Emergency stop switch or engine shutdown switch activated | Verify that it is safe to start the engine and apply load; Then reset the stop switch or engine shutdown switch |
| Overcrank fault | Generator set does not start in three attempts (three starting attempts, 15 seconds crank and 15 seconds off) | Reset the controller; If the overcrank fault occurs again, contact an authorized distributor/dealer |
| Underspeed, underfrequency, or undervoltage fault | Enclosure thermostat tripped due to excess heat inside the enclosure | Check for blocked air inlets and exhaust outlets; Reset the thermostat |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Low oil pressure shutdown; Out of fuel; Overcrank shutdown; Auxiliary winding circuit breaker tripped. See the table for the matching fixes.
Documented causes: Air cleaner clogged; Battery weak or dead; Battery connection poor; Spark plug wire connection loose. See the table for the matching fixes.
Documented causes: Battery weak or dead; Battery connections reversed or poor; Fault shutdown; Generator set in the OFF mode. See the table for the matching fixes.