Thermo Products MG-1018 Iii.Ecm Trouble Shooting, Symptom, Cause/Procedure, Motor won’t start

All installations and services must be performed by qualified service personnel.

III.ECM TROUBLE SHOOTING

A. GENERAL GUIDELINES TO TROUBLESHOOTING GE ECM – DRIVEN SYSTEMS

: Disconnect power from unit before removing or replacing connectors, or servicing motor. Wait at least 5 minutes after disconnecting power before opening motor.

	SYMPTOM		CAUSE/PROCEDURE
Motor rocks slightly when starting		•	This is normal start-up for ECM
Motor won’t start		•	Check power at motor
•	No movement	•	Check low voltage (24 VAC R to C) at motor
		•	Check low voltage connections (G,Y,W,R,C,) at
		•	motor
			Check for unseated pins in connectors on motor
		•	harness
			Test with a temporary jumper between R – G
		•	Check motor for tight shaft
		•	Perform motor/control replacement check
		•	Run Moisture Check
•	Motor rocks, but won’t start	•	Check for loose or compliant motor mount
		•	Make sure blower wheel is tight on shaft
		•	Perform motor/control replacement check
Motor oscillates up & down while being tested off		•	It is normal for motor to oscillate with no load on
of blower			shaft.
Motor starts, but runs erratically
•	Varies up and down or intermittent	•	Check line voltage for variation or “sag”
		•	Check low voltage connections (G,Y,W,R,C,) at
		•	motor, unseated pins in motor harness connectors
			Check “Bk” for erratic CFM command (in
		•	variable speed applications)
			Check-out system controls – T’stat?
		•	Perform Moisture Check
•	“Hunts” or “puffs” at high CFM (speed)	•	Does removing panel or filter reduce “puffing”?
			! Reduce restriction
			! Reduce max airflow
•	Stays at low CFM despite system call for cool or	•	Check low voltage (T’stat) wires and connections
	heat CFM	•	Verify fan is not in delay mode – wait until delay
		•	complete
			“R” missing/not connected at motor
		•	Perform motor/control replacement check
•	Stays at high CFM	•	“R” missing/not connected at motor
		•	Is fan in delay mode? – wait until delay time
		•	complete
			Perform motor/control replacement check
•	Blower won’t shut off	•	Current leakage from controls into G,Y or W?
			Check for Triac switched t’stat or solid state relay
Excessive noise		•	Determine if it’s air noise, cabinet, duct or motor
			noise – interview customer, if necessary
•	Noisy blower or cabinet	•	Check for loose blower housing, panels, etc.
		•	High static creating high blower speed?
			! Check for air whistling thru seams in ducts,
			cabinets or panels
			! Check for cabinet/duct deformation

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