Atlas Copco QAS 38 troubleshooting: 17 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Atlas Copco QAS 38 — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| The starter motor turns the engine too slowly | - Battery capacity too low. - Bad electrical connection. - Fault in starter motor. - Wrong grade of lubricating oil. | |
| The engine does not start or is difficult to start | - Starter motor turns engine too slowly. - Fuel tank empty. - Fault in fuel control solenoid. - Restriction in a fuel pipe. - Fault in fuel lift pump. - Dirty fuel filter element. - Air in fuel system. - Fault in atomisers. - Cold start system used incorrectly. - Fault in cold start system. - Restriction in fuel tank vent. - Wrong type or grade of fuel used. - Restriction in exhaust pipe. | |
| Not enough power | - Restriction in a fuel pipe. - Fault in fuel lift pump. - Dirty fuel filter element. - Restriction in air filter/cleaner or induction system. - Air in fuel system. | |
| Alternator does not excite | - Blown fuse. | Replace fuse. |
| Insufficient residual voltage | Increase the speed by 15 %. | |
| No residual voltage | For an instant apply on the + and – terminals of the electronic regulator a 12 V battery voltage with a 30 Ω resistor in series respecting the polarities. | |
| After being excited alternator does not excite | - Connections are interrupted. | Check connection cables as per attached drawings. |
| Low voltage at no load | - Voltage potentiometer out of setting. | Reset voltage. |
| High voltage at no load | - Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Lower than rated voltage at load | - Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Current too high, power factor lower than 0.8; speed lower than 10 % of rated speed | - Failed regulator. | Substitute regulator. |
| Rotating bridge failure | - Check diodes, disconnect cables. | |
| Higher than rated voltage at load | - Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Loose sensing wires on AVR | Check sensing wires on AVR. | |
| Failed regulator | Substitute regulator. | |
| Unstable voltage | - Speed variation in engine. | Check regularity of rotation. |
| Regulator out of setting | Regulate stability of regulator by acting on “STABILITY” potentiometer. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: - Battery capacity too low. - Bad electrical connection. - Fault in starter motor. - Wrong grade of lubricating oil.. See the table for the matching fixes.
Documented causes: - Starter motor turns engine too slowly. - Fuel tank empty. - Fault in fuel control solenoid. - Restriction in a fuel pipe. - Fault in fuel lift pump. - Dirty fuel filter element. - Air in fuel system. - Fault in atomisers. - Cold start system used incorrectly. - Fault in cold start system. - Restriction in fuel tank vent. - Wrong type or grade of fuel used. - Restriction in exhaust 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. - Air in fuel system.. See the table for the matching fixes.