Atlas Copco QAS 45 KD troubleshooting: 111 symptom-cause-remedy entries from the manufacturer's own service documentation.
Atlas Copco QAS 45 KD — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| Alternator gives 0 Volt | Blown fuse | Replace fuse |
| Alternator gives 0 Volt | No residual voltage | Excite the alternator by applying a 12V battery voltage with a 30 W resistor in series on the + and - terminals of the electronic regulator, respecting the polarities |
| After being excited the alternator still gives 0 Volt | Connections are interrupted | Check connection cables, measure winding resistances and compare with values mentioned in the alternator manual |
| Low voltage at no load | Voltage potentiometer out of setting | Reset voltage |
| Low voltage at no load | Intervention of protection | Check frequency/voltage regulator |
| Low voltage at no load | Winding failure | Check windings |
| High voltage at no load | Voltage potentiometer out of setting | Reset voltage |
| High voltage at no load | Failed regulator | Substitute regulator |
| Lower than rated voltage at load | Voltage potentiometer out of setting | Reset voltage potentiometer |
| Lower than rated voltage at load | Intervention by protection | Current too high, power factor lower than 0.8; speed lower than 10% of rated speed |
| Lower than rated voltage at load | Failed regulator | Substitute regulator |
| Lower than rated voltage at load | Rotating bridge failure | Check diodes, disconnect cables |
| Higher than rated voltage at load | Voltage potentiometer out of setting | Reset voltage potentiometer |
| Higher than rated voltage at load | Failed regulator | Substitute regulator |
| Unstable voltage | Speed variation in engine | Check regularity of rotation |
| Unstable voltage | Regulator out of setting | Regulate stability of regulator by acting on STABILITY potentiometer |
| The starter motor turns the engine too slowly | Battery capacity too low | |
| The starter motor turns the engine too slowly | Bad electrical connection | |
| The starter motor turns the engine too slowly | Fault in starter motor | |
| The starter motor turns the engine too slowly | Wrong grade of lubricating oil | |
| The engine does not start or is difficult to start | Starter motor turns engine too slowly | |
| The engine does not start or is difficult to start | Fuel tank empty | |
| The engine does not start or is difficult to start | Fault in fuel control solenoid | |
| The engine does not start or is difficult to start | Restriction in a fuel pipe | |
| The engine does not start or is difficult to start | Fault in fuel lift pump | |
| The engine does not start or is difficult to start | Dirty fuel filter element | |
| The engine does not start or is difficult to start | Air in fuel system | |
| The engine does not start or is difficult to start | Fault in atomisers | |
| The engine does not start or is difficult to start | Cold start system used incorrectly | |
| The engine does not start or is difficult to start | Fault in cold start system | |
| The engine does not start or is difficult to start | Restriction in fuel tank vent | |
| The engine does not start or is difficult to start | Wrong type or grade of fuel used | |
| The engine does not start or is difficult to start | Restriction in exhaust pipe | |
| Not enough power | Restriction in a fuel pipe | |
| Not enough power | Fault in fuel lift pump | |
| Not enough power | Dirty fuel filter element | |
| Not enough power | Restriction in air filter/cleaner or induction system | |
| Not enough power | Air in fuel system | |
| Not enough power | Fault in atomisers or atomisers of an incorrect type | |
| Not enough power | Restriction in fuel tank vent | |
| Not enough power | Wrong type or grade of fuel used | |
| Not enough power | Restricted movement of engine speed control | |
| Not enough power | Restriction in exhaust pipe | |
| Not enough power | Engine temperature is too high | |
| Not enough power | Engine temperature is too low | |
| Misfire | Restriction in a fuel pipe | |
| Misfire | Fault in fuel lift pump | |
| Misfire | Dirty fuel filter element | |
| Misfire | Air in fuel system | |
| Misfire | Fault in atomisers or atomisers of an incorrect type | |
| Misfire | Fault in cold start system | |
| Misfire | Engine temperature is too high | |
| Misfire | Incorrect valve tip clearances | |
| The pressure of the lubricating oil is too low | Wrong grade of lubricating oil | |
| The pressure of the lubricating oil is too low | Not enough lubricating oil in sump | |
| The pressure of the lubricating oil is too low | Defective gauge | |
| The pressure of the lubricating oil is too low | Dirty lubricating oil filter element | |
| High fuel consumption | Restriction in air filter/cleaner or induction system | |
| High fuel consumption | Fault in atomisers or atomisers of an incorrect type | |
| High fuel consumption | Fault in cold start system | |
| High fuel consumption | Wrong type or grade of fuel used | |
| High fuel consumption | Restricted movement of engine speed control | |
| High fuel consumption | Restriction in exhaust pipe | |
| High fuel consumption | Engine temperature is too low | |
| High fuel consumption | Incorrect valve tip clearances | |
| Black exhaust smoke | Restriction in air filter/cleaner or induction system | |
| Black exhaust smoke | Fault in atomisers or atomisers of an incorrect type | |
| Black exhaust smoke | Fault in cold start system | |
| Black exhaust smoke | Wrong type or grade of fuel used | |
| Black exhaust smoke | Restriction in exhaust pipe | |
| Black exhaust smoke | Engine temperature is too low | |
| Black exhaust smoke | Incorrect valve tip clearances | |
| Black exhaust smoke | Engine overload | |
| Blue or white exhaust smoke | Wrong grade of lubricating oil | |
| Blue or white exhaust smoke | Fault in cold start system | |
| Blue or white exhaust smoke | Engine temperature is too low | |
| The engine knocks | Fault in fuel lift pump | |
| The engine knocks | Fault in atomisers or atomisers of an incorrect type | |
| The engine knocks | Fault in cold start system | |
| The engine knocks | Wrong type or grade of fuel used | |
| The engine knocks | Engine temperature is too high | |
| The engine knocks | Incorrect valve tip clearances | |
| The engine runs erratically | Fault in fuel control | |
| The engine runs erratically | Restriction in a fuel pipe | |
| The engine runs erratically | Fault in fuel lift pump | |
| The engine runs erratically | Dirty fuel filter element | |
| The engine runs erratically | Restriction in air filter/cleaner or induction system | |
| The engine runs erratically | Air in fuel system | |
| The engine runs erratically | Fault in atomisers or atomisers of an incorrect type | |
| The engine runs erratically | Fault in cold start system | |
| The engine runs erratically | Restriction in fuel tank vent | |
| The engine runs erratically | Restricted movement of engine speed control | |
| The engine runs erratically | Engine temperature is too high | |
| The engine runs erratically | Incorrect valve tip clearances | |
| Vibration | Fault in atomisers or atomisers of an incorrect type | |
| Vibration | Restricted movement of engine speed control | |
| Vibration | Engine temperature is too high | |
| Vibration | Fan damaged | |
| Vibration | Fault in engine mounting or flywheel housing | |
| The pressure of the lubricating oil is too high | Wrong grade of lubricating oil | |
| The pressure of the lubricating oil is too high | Defective gauge | |
| The engine temperature is too high | Restriction in air filter/cleaner or induction system | |
| The engine temperature is too high | Fault in atomisers or atomisers of an incorrect type | |
| The engine temperature is too high | Fault in cold start system | |
| The engine temperature is too high | Restriction in exhaust pipe | |
| The engine temperature is too high | Fan damaged | |
| The engine temperature is too high | Too much lubricating oil in sump | |
| The engine temperature is too high | Restriction in air or coolant passages of radiator | |
| The engine temperature is too high | Insufficient coolant in system | |
| Crankcase pressure | Restriction in breather pipe | |
| Crankcase pressure | Vacuum pipe leaks |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Starter motor turns engine too slowly; Fuel tank empty; Fault in fuel control solenoid; Restriction in a fuel pipe. See the table for the matching fixes.
Documented causes: Restriction in a fuel pipe; Fault in fuel lift pump; Dirty fuel filter element; Restriction in air filter/cleaner or induction system. See the table for the matching fixes.
Documented causes: Fault in fuel control; Restriction in a fuel pipe; Fault in fuel lift pump; Dirty fuel filter element. See the table for the matching fixes.