The Microcomputer is a generator-set controller. It is used on generator sets from Kohler, including the Fast-Response I.
| Code | Meaning | Cause |
|---|---|---|
| F1 | F1 Fuse - Remote Annunciator (3 Amp.) blown | Defective Decision Monitor; Defective Remote Annunciator; Defective Audio-Visual Alarm (accessories connected to controller TB42A) |
| F2 | F2 - Controller (3 Amp.) blown | Shorted speed sensor; Shorted DC supply to indicator panel; Shorted controller circuit board |
| F3 | F3 - Engine and Accessories (15 Amp.) blown | If equipped with K4 (emergency stop) relay: Defective engine electrics; Defective overvoltage board; Defective circuit board |
| F3 | F3 - Engine and Accessories (15 Amp.) blown (genset not equipped with K4 relay) | Defective gauges; Defective safeguard breaker/voltage regulator; Defective engine run circuit; Defective crank circuit |
| Symptom | Cause | Remedy |
|---|---|---|
| A1 and A2 leads damaged or open | Damaged or open exciter armature leads | Repair A1 and A2 leads; solder and insulate splices; use new sleeving when tying leads to shaft or heat sink |
| A1 or A2 leads shorted to ground | Grounded exciter armature | Repair A1 and A2 leads; solder and insulate splices; use new sleeving when tying leads to shaft or heat sink; replace rotor assembly if test should show armature shorted or grounded |
| AVR not functioning properly | 15 Amp. fuse (if equipped) blown | Check 15 Amp. fuse (if equipped) |
| AVR not functioning properly (AC voltage does not decline when engine speed drops below approximately 58 Hz at 60 Hz operation or 48 Hz at 50 Hz operation) | Open or shorted circuit between leads V7 and V8 (voltage sensing leads) from voltage regulator (AVR) to controller terminal strip | If these circuits are open or shorted, repair or replace |
| Battery Charger Fault (if battery charger equipped) | Generator Master Switch in OFF/RESET; engine switch in RUN position. Ground controller terminal TB 61 to test. If Battery Charger lamp lights, circuit is functioning properly. | |
| Ceiling voltage is not read during flashlight test | Exciter armature faulty | Go to exciter armature test |
| Continuity between field leads and rotor assembly | Grounded generator field | Repair F3 and F4 if test should show leads shorted to ground; solder and insulate splices; use new sleeving when tying leads to shaft or heat sink; replace generator rotor assembly if tests show a short or ground |
| Engine cranks but will not start | Low fuel | Check fuel supply, replenish as necessary. |
| Engine starts and runs, but overcrank lamp flashes | K3 relay not energizing | Verify voltage to relay. If voltage at relay, check resistance of relay coil (see relay coil and voltage check preceding). |
| Engine starts and runs, but stops after approximately 25 seconds | Excessive speed sensor air gap | Adjust to 0.020 in. (0.508 mm). See Figure 3-7. |
| Engine will not crank with Generator Master Switch in RUN position (circuit board receiving power - relays energized) | Fault shutdown: High Engine Temperature, Low Oil Pressure, Overspeed, Overcrank, Low Coolant Level, High Engine Oil Temperature or Overvoltage | Correct fault - See "Resetting" procedure in Section 2. |
| Engine will not crank with Master Switch in RUN position (no power to controller circuit board) | Battery weak or dead | Recharge or replace battery. Verify proper operation of battery charger. |
| Engine will not crank with master switch in TEST position (CR and 1CR relays not energizing) | Battery weak or dead | Recharge or replace battery. Check battery charger. |
| Exciter armature faulty | Shorted winding(s); low resistance readings (under 0.1-0.2 ohms) | Replacement of rotor assembly |
| Exciter armature leads damaged or open | Damaged or open A1 and A2 leads (one-piece activator) or AC leads (split activator) | Repair A1 and A2 leads (one-piece activator) or AC leads (split activator); solder and insulate splices; use new sleeving when tying leads to shaft or heat sink |
| Exciter armature leads shorted to ground | Leads shorted to ground | Repair A1 and A2 or AC leads; solder and insulate splices; use new sleeving when tying leads to shaft or heat sink |
| Exciter armature shorted or grounded | Armature shorted or grounded | Replace rotor assembly |
| Exciter armature winding insulation deteriorated (megohmmeter reading less than 500K ohms approx. to rotor shaft and A1 or A2 lead or either AC lead) | Deterioration of winding insulation and possible current flow to ground | Repair or replacement of the rotor is necessary |
| FR activator defective | No continuity between terminals E and F3 of the FR activator with leads disconnected | Generator rotor is shorted to ground; replace or repair generator rotor assembly and replace FR activator |
| Fluctuating Voltage | Improper connections of generator output leads | Check the generator output leads for proper connections (refer to Section 7, Wiring Diagrams) |
| Fluctuating voltage | Generator output leads improperly connected | Check the generator output leads for proper connections (refer to Section 7, Wiring Diagrams) |
| Fuse blows — generator set will stop; unit will not crank with a blown fuse | Wiring short circuit or circuit overload | If set has stopped due to causes other than lack of fuel, or fault shut-down—check the fuse. If blown, replace the fuse and attempt to restart generator set. If the set will not start, or if the fuse blows again, locate and correct the cause. |
| Generator field winding insulation deteriorated (megohmmeter reading less than 500K ohms approx. to F3 or F4 lead or F+ and F-) | Deterioration of winding insulation and possible current flow to ground | Repair or replacement of the rotor assembly is necessary |
| Generator set inoperable — 1-Amp fuse will blow | Battery connections reversed (negative ground control system) | |
| Grounded generator field | Continuity between field leads and rotor assembly | Repair F3 and F4 (one-piece activator) or F+ and F- (split activator) if test shows leads shorted to ground; solder and insulate splices; use new sleeving when tying leads to shaft or heat sink; replace generator rotor assembly if tests show a short or ground |
| High resistance across "A", or continuity across "B" and ground | Open windings; faulty stator | Replace stator |
| High water temperature fault shutdown — HWT contacts close, 1TS switch times out causing CR relay to deenergize, reset lamp lights, CR relay contacts open shutting off fuel solenoid or ignition coil | High water temperature | |
| Instrumentation not functioning properly | Loose input or instrument lead connection at AC Fuse Terminal Block (TB3) | Check connections at AC Fuse Terminal Block (TB3). |
| Lamp circuit board not functioning (fault lamps and alarm horn) | No input voltage to lamp circuit board. If no fault lamps illuminate when lamp test switch is pressed, check for input voltage on lamp circuit board. | If lamp circuit board is receiving input voltage, lamp circuit board may be defective. If lamp circuit board is not receiving input voltage, refer to microcomputer circuit board troubleshooting procedure covered previously in table. |
| Low Battery Volts (if battery charger equipped) | Generator Master Switch in OFF/RESET; engine switch in RUN. Ground controller terminal TB 62 to test. If Low Battery Volts lamp lights, circuit is functioning properly. | |
| Low coolant level fault shutdown (if equipped) — coolant level switch closes, 1TS switch times out causing CR relay to deenergize, reset lamp lights, CR relay contacts open shutting off fuel solenoid or ignition coil | Low coolant level | |
| Low oil pressure fault shutdown — LOP contacts close, 1TS switch times out causing CR relay to deenergize, CR relay contacts open shutting off fuel solenoid or ignition coil, reset lamp lights | Low oil pressure | |
| Low resistance readings (under 0.1-0.2 ohms) across A1 and A2 | Shorted exciter armature winding | Replace rotor assembly |
| No DC voltage observed at 3B (+) and 5B (-) at the LED board | AVR not functioning properly | Refer to the AVR test |
| No continuity between terminals E and F3 of the FR Activator with leads disconnected | FR Activator defective and/or generator rotor shorted to ground | Replace or repair generator rotor assembly and replace FR Activator |
| No output observed during LED flashlight test | Photo transistor board or FR Activator faulty | Check the photo transistor board and the FR Activator |
| No output on any phase | Safeguard breaker open (if equipped) | Close the safeguard breaker, and with set running check AC voltmeter for proper output voltage |
| No voltage at K1 - solenoid coil | Open CR, 1CR, or CC contacts in series with SS solenoid. Open in P5 connector (pin 4). Open in P1 connector (pin 16). | Repair or replace. |
| No voltage read at 3B/5B connector points | Wiring faulty or voltage regulator faulty | Repair wiring or replace voltage regulator |
| No voltage reading at 1B (+) and 7N (-) at the voltage regulator harness plug | Wiring to the Safeguard breaker, CR relay or 15-Amp fuse faulty | Check the wiring to the Safeguard breaker, CR relay or 15-Amp fuse |
| Ohmmeter does not respond during photo transistor board test | Meter polarity may be reversed | Reverse ohmmeter leads and repeat check |
| Output does not drop to low voltage when flashlight is removed | FR Activator faulty | Replace FR Activator. See "FR Activator". |
| Over-voltage | Problem lies in photo transistor circuit and/or FR-Activator (over-voltage continues after disconnecting harness plug at voltage regulator) | See "Component Testing" |
| Overcrank fault shutdown — after 30-60 seconds of cranking the 1CR relay will not energize, 1TS times out causing CR relay to deenergize, reset lamp lights, CR relay contacts open shutting off SS relay, fuel solenoid or ignition coil | Engine does not start after 30-60 seconds of cranking | |
| Overvoltage | Problem lies in the photo transistor circuit and/or FR activator (overvoltage continues with harness plug disconnected at AVR) | Proceed through the following checks |
| Overvoltage - Generators with Split FR Activator | Photo transistor board visibly damaged (open foil pattern, heat discoloration) | Replace photo transistor board if visibly damaged; if overvoltage continues after replacement, proceed to step 2 |
| Overvoltage - Generators with Standard FR Activator | Grounded "C" lead on photo transistor board | Check the photo transistor board for a grounded "C" lead; check the photo transistor board as described in "Component Testing" |
| Photo transistor board does not respond (ohmmeter does not respond after reversing leads) | Defective photo transistor board | Replace photo transistor board and harness assembly |
| Resistance across F3 and F4 leads not 2-3.75 ohms, + 5% | Generator field faulty | Repair or replace as necessary |
| Safeguard breaker opens — battery voltage is shut off to the voltage regulator resulting in a loss of generator AC output; 1CR relay deenergizes, 1TS switch times out in approximately 30-60 seconds and trips causing the CR relay to deenergize, reset lamp will light, engine stops | Sustained overload or short circuit sensed by Safeguard Breaker | |
| Split FR activator component of unknown quality defective (test fixture light bulb does not light or is lit prior to receiving external light source) | Defective activator component being tested (e.g., SCR assembly) | Replace the SCR assembly |
| Stator open windings | High resistance across "A" or continuity across "B" and ground | Replace stator |
| Stator shorted windings | Burnt or hot windings | Replace stator if windings are burnt or hot |
| Stator windings burnt or hot | Shorted windings | Replace stator if windings are burnt or hot |
| Unit cranks but will not start | No fuel | Check for fuel at pump or carburetor. Check for clogged fuel filter. Check engine fuel system. |
| Unit runs for 30-60 seconds then shuts down | No AC output available to 1CR relay coil. Safeguard breaker (if equipped) must be closed. | Check for 120 volts AC to controller terminal strip V0 and V8. See generator troubleshooting (No Output). If 1CR relay does not energize, normally closed contact of relay will energize 1TS thermal switch and shut down unit. |
Fault codes and symptom→remedy steps extracted from this controller’s service/owner documentation; verify against the official manual before servicing. Aggregated from the service documentation of generator sets built on this controller.