John Deere QAS 330 troubleshooting: 14 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
John Deere QAS 330 — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| Alternator does not excite | Blown fuse. | Replace fuse. |
| 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. | |
| Low voltage at no load | Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Intervention of protection. | Check rpm. | |
| Winding failure. | Check windings. | |
| High voltage at no load | Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Failed regulator. | Substitute regulator. | |
| Lower than rated voltage at load | Voltage potentiometer out of setting. | Reset voltage potentiometer. |
| Intervention by protection. | 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. |
| Unstable voltage | Speed variation in engine. | Check regularity of rotation. |
| Checking voltmeter P4 | Put a voltmeter in parallel with voltmeter P4 on the control panel. Check that the read-out of both voltmeters is the same. Stop the generator and disconnect one terminal. Check that the internal resistance of the voltmeter is high. | |
| Checking ammeters P1, P2 and P3 | Measure by means of a clamp-on probe the outgoing current during the load. Compare the measured currents with the currents on the corresponding ammeters. Both readings should be the same. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Blown fuse.. See the table for the matching fixes.
Documented causes: Voltage potentiometer out of setting.. See the table for the matching fixes.
Documented causes: Voltage potentiometer out of setting.. See the table for the matching fixes.