Problem: GS3 Auto-Tune Returns --ERR-- in Sensorless Vector Mode
On AutomationDirect GS3 series VFDs (e.g., GS3-21P0, 1.0 HP / 240 V single-phase input), setting P0.05 = 1 (static auto-tune) or P0.05 = 2 (rotational auto-tune) while P2.10 = 2 (sensorless vector control) triggers a --ERR-- fault on the keypad display instead of executing the tuning routine. The drive does not run the motor and no fault code number is stored in the fault history.
--ERR-- during auto-tune is a pre-run parameter validation failure — not a runtime trip. The drive refuses to start the test sequence because one or more preconditions are unmet. Do not attempt to force a run command while in this state.Root Causes
| Root Cause | Parameter to Check | Required Condition |
|---|---|---|
| Motor nameplate data out of range or missing | P0.00–P0.04 | All five parameters populated; values must match motor nameplate |
| Rated current (P0.01) exceeds drive output rating | P0.01 | ≤ drive rated output current (GS3-21P0: 6.0 A) |
| Rated frequency (P0.02) not 50/60 Hz | P0.02 | Must be 50.00 or 60.00 Hz; non-standard values rejected |
| Control mode not sensorless vector before tune | P2.10 | Set to 2 before writing P0.05; some firmware requires power cycle after P2.10 change |
| Run/stop source not keypad | P2.01 | Set to 0 (keypad) for auto-tune; external terminal or serial run commands block tune |
| Motor not connected or output open | Hardware | Motor must be wired to T1/T2/T3; open output lines cause immediate --ERR-- |
| Drive in fault state from previous trip | Fault history | Clear all faults before initiating tune; press STOP/RESET or cycle power |
| Parameter P0.05 written while drive is in RUN state | P0.05 | Drive must be stopped (STOP LED on) before writing auto-tune command |
GS3-21P0 Motor Parameter Requirements (P0.00–P0.04)
All five motor parameters must be entered from the motor nameplate before auto-tune will accept P0.05. The GS3 validates plausibility across all five values simultaneously.
| Parameter | Description | Typical 1 HP / 230 V Value | Range |
|---|---|---|---|
P0.00 |
Motor rated power (HP) | 1.0 | 0.1–500.0 HP |
P0.01 |
Motor rated current (A) | 4.0–5.8 A (nameplate) | 0.1–999.9 A |
P0.02 |
Motor rated frequency (Hz) | 60.00 | 10.00–400.0 Hz |
P0.03 |
Motor rated speed (RPM) | 1725 or 1750 | 0–65535 RPM |
P0.04 |
Motor rated voltage (V) | 230 | 0–255 V (240 V class) |
Step-by-Step Auto-Tune Procedure
- Verify motor wiring. Confirm T1, T2, T3 are connected to motor leads U, V, W. Check for open or shorted phases with a multimeter (expect 0.5–5 Ω phase-to-phase on most NEMA motors).
-
Clear all faults. Press the STOP/RESET key or cycle 24 VDC control power. Confirm keypad shows
0.00(stopped, no fault). -
Set run source to keypad. Set
P2.01 = 0. This prevents external signals from interfering with the tune sequence. -
Set frequency source to keypad. Set
P2.00 = 0(keypad potentiometer or numeric entry). -
Enter motor nameplate data. Program
P0.00throughP0.04exactly as printed on the motor nameplate. Cross-check P0.01 ≤ 6.0 A for GS3-21P0. -
Set control mode. Set
P2.10 = 2(sensorless vector). If this parameter was previously set differently, cycle drive power after changing it — some firmware versions require a power cycle to fully initialize the vector algorithm. - Confirm drive is stopped. STOP LED must be illuminated. Do not attempt to write P0.05 while the drive is running or in jog mode.
-
Initiate static auto-tune. Set
P0.05 = 1for static tune (motor shaft does not rotate — safe for coupled loads). Press RUN. The display will cycle through test phases and then return to0.00when complete. -
Optional — rotational tune: Set
P0.05 = 2only if the motor can spin freely (unloaded or decoupled). This provides higher-accuracy stator resistance, leakage inductance, and iron loss data. -
Verify completion. After successful tune,
P0.05automatically resets to0. ParametersP0.06–P0.10(Rs, Rr, Lm, Lx, no-load current) will be populated with measured values. Confirm these are non-zero.
Verification and Post-Tune Checks
After a successful auto-tune, confirm the following motor equivalent circuit parameters are populated (non-zero). If any remain at default, the tune did not complete correctly:
| Parameter | Description | Expected (non-zero) |
|---|---|---|
P0.06 |
Stator resistance Rs (Ω) | Typically 0.5–10 Ω for NEMA motors |
P0.07 |
Rotor resistance Rr (Ω) | Typically 0.3–8 Ω |
P0.08 |
Magnetizing inductance Lm (mH) | Typically 50–500 mH |
P0.09 |
Stator/rotor leakage Lx (mH) | Typically 1–50 mH |
P0.10 |
No-load current Io (A) | Typically 20–50% of P0.01 |
Run the motor at 30 Hz with no load. Confirm stable speed response and no hunting or oscillation. If oscillation occurs, reduce P2.11 (vector control gain) by 10–20% from default.
P9.08 = 1 (reset all parameters to factory default). Re-enter motor data and repeat the procedure. Reference: AutomationDirect GS3 User Manual (gs3m.pdf).FAQ
Why does GS3 show --ERR-- when I set P0.05 to 1 or 2?
--ERR-- means the drive failed a pre-run parameter validation. Most common causes: motor data in P0.00–P0.04 is incomplete or out of range, the motor is not connected to T1/T2/T3, or the drive was not fully stopped before writing P0.05. Verify all five motor nameplate parameters match the actual motor and that P0.01 does not exceed the drive's output current rating (6.0 A for GS3-21P0).
Do I need to power-cycle the GS3 after changing P2.10 to sensorless vector mode?
Yes — cycle control power after setting P2.10 = 2 before attempting auto-tune. Some GS3 firmware versions do not fully activate the sensorless vector algorithm until the drive reinitializes. Failure to power-cycle can result in --ERR-- even with correct motor parameters.
Can I run P0.05 = 2 (rotational auto-tune) with the motor coupled to a load?
No. Rotational auto-tune (P0.05 = 2) spins the motor shaft during the test sequence. Decouple the load or use static tune (P0.05 = 1) instead. Static tune measures stator resistance with the shaft locked and is sufficient for most sensorless vector applications.
What motor parameters go into P0.00 through P0.04 on the GS3?
P0.00 = rated HP, P0.01 = rated current (A), P0.02 = rated frequency (Hz), P0.03 = rated speed (RPM), P0.04 = rated voltage (V). All values come directly from the motor nameplate. See the GS3 User Manual Section 4 for valid ranges.
Where are the auto-tune results stored on the GS3, and how do I verify a successful tune?
Results are stored in P0.06 (Rs), P0.07 (Rr), P0.08 (Lm), P0.09 (Lx), and P0.10 (Io). After a successful tune, P0.05 resets to 0 automatically and all five result parameters will contain non-zero measured values. If any remain at 0, the tune did not complete and must be re-initiated.