What causes fault code VFD-ETEMP1 (VFD External Thermistor Trip — Motor PTC)?

Motor genuinely overheated — overloaded, poor ventilation, or high ambient. PTC thermistor wiring open — broken wire reads as high resistance (hot) to VFD. Motor cooling fan failed — TEFC fan shroud clogged or fan broken. Motor running at low speed too long — insufficient self-cooling below 30Hz. PTC thermistor in motor is degraded — resistance drifted with age

How do I fix fault code VFD-ETEMP1?

Check motor surface temperature with IR gun — verify it is actually hot. If motor is cool, check PTC wiring from motor to VFD thermistor input — look for broken wire or loose terminal. Measure PTC resistance at VFD terminals — should be <1.5K ohm when motor is cool, >3.3K ohm when hot (typical PTC trip point). Inspect motor fan and fan shroud — clean and verify fan operation. If motor runs at low speeds continuously, install external forced cooling blower. Replace PTC sensor only if resistance is erratic when motor is at known temperature

VFD External Thermistor Trip — Motor PTC

VFD-ETEMP1

VFD thermistor input detected motor over-temperature via embedded PTC or PT100 sensor in motor windings.

medium vfd motor

vfd thermistor ptc motor temperature overheating

Probable Causes (ranked)

Motor genuinely overheated — overloaded, poor ventilation, or high ambient
PTC thermistor wiring open — broken wire reads as high resistance (hot) to VFD
Motor cooling fan failed — TEFC fan shroud clogged or fan broken
Motor running at low speed too long — insufficient self-cooling below 30Hz
PTC thermistor in motor is degraded — resistance drifted with age

Fix Steps

1 Check motor surface temperature with IR gun — verify it is actually hot
2 If motor is cool, check PTC wiring from motor to VFD thermistor input — look for broken wire or loose terminal
3 Measure PTC resistance at VFD terminals — should be <1.5K ohm when motor is cool, >3.3K ohm when hot (typical PTC trip point)
4 Inspect motor fan and fan shroud — clean and verify fan operation
5 If motor runs at low speeds continuously, install external forced cooling blower
6 Replace PTC sensor only if resistance is erratic when motor is at known temperature

Field Trick

PTC thermistors in motors fail open more often than motors actually overheat. Before blaming the motor, jumper the PTC input at the VFD with a 1K ohm resistor. If the fault clears and the motor runs cool, the PTC or its wiring is the problem, not the motor.

Suggested Replacement Parts

Parts matched to fault category: Motor

Baldor/ABB 1HP TEFC Motor P/N: EM3554T 1HP, 1765RPM, 143TC frame, 230/460V, TEFC, premium efficiency

AutomationDirect $285.00 Amazon $310.00 Grainger $345.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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