Electrical & Logic | Module 216

EEV Stepper Motor Winding Resistance Mapping

Field Status: The Electronic Expansion Valve (EEV) is driven by a 4-pole or 5-pole stepper motor. Unlike standard coils, this motor moves in precise increments (“steps”) based on DC pulses from the control board. If one of the internal stator coils burns out, the motor will “slip” or jam, leaving the valve stuck in a partially open or closed position, resulting in massive suction pressure swings.

A healthy EEV stepper coil should read an identical resistance value across its phases (usually 40–150 Ohms). Use your multimeter in Ohm mode to map the coil. If any winding pair reads “OL” (open) or significantly different than the others, the motor is failing.

SYS AUDIT: Stator Resistance Audit
STATOR STATUS: —
—

The “Tick” Diagnostic

When an inverter system powers up, it performs an EEV “reset” by sending enough pulses to drive the valve fully closed. If you place your hand on the EEV motor head during startup, you should feel a distinct, rapid “ticking” vibration. This vibration proves the pulses are reaching the motor. If it is silent but the coils test good, the board is not sending the pulse signal.

SymptomElectrical ResistanceConclusion
Coil Open (OL)Infinite ΩCondemn motor.
Coil Shorted< 5 ΩCondemn motor and driver board.
Coil Balanced40–150 ΩMechanical jam or board pulse failure.

Diagnostic Gateway Challenge

Your EEV coils test perfectly balanced at 45 Ohms each. You energize the system, and you feel the “ticking” vibration in the motor head, but suction pressures remain erratic. What is the most likely culprit?

END OF MODULE 216

← Return to Open-Access Repository

Request Professional Audit

CONTACT SUPPORT