Sterling Water Heater Troubleshooting Quick Guide, Reference Manual PN 682.89373.00 for

	Micro Series Water Temperature Control Units
	Reference Manual (PN: 682.89373.00) for
	Complete Operation and Installation Instructions
	(Available online at www.sterlco.com)
	Troubleshooting - Quick Guide
Problem	Possible cause	Solution
	No power.	Check main disconnect, fuses, wiring, and
		power lead to unit.
	Wrong voltage supplied to unit.	Voltage must be within plus or minus 10% of
Unit does not turn on		nameplate rating.
	Defective on/off switch.	Replace.
	Control circuit fuse blown.	Replace.
	Defective control transformer.	Check transformer.
	Broken or loose wire in pump motor control circuit.	Locate and repair.
	Pump motor contactor holding coil is open.	Repair or replace.
		Check for at least 16 psig (110.32 kPa/1.1
Unit does not run	Low water pressure light on.	bars) water pressure on WATER IN or CITY
		WATER MAKEUP.
	Water supply to unit is turned off.	Open water supply.
	Pump overload light on.	Reset and test each leg for balanced amp
		draws.
	Undersized connectors/ water lines.	Increase size of connectors/ water lines.
	Long connecting lines between unit and mold.	Move the unit closer to the mold and shorten
		connecting lines.
Temperature fluctuations/
	Serpentine flow through mold.	Connect lines for parallel flow instead of
rapid cycling from hot to		series flow.
cold.
	Blocked water line in mold.	Check mold for metal chips or lime buildup.
		Clean mold.
	Quick disconnect fitting with check valve.	Remove and replace fitting or valve.
	Lime buildup in unit piping.	Clean or replace.
	Drain is plugged or excessive back pressure is in drain	Clear drain line or eliminate back pressure
	line.	condition.
	Faulty solenoid valve.	Test solenoid valve by pressing VENT
		button and listen for valve operation.
		Replace if faulty.
	Controller Cool output relay open.	Replace output relay.
Unit overheats or does not	Solenoid valve is not operating, but COOL LED is on.	Set process temperature to minimum and
		check for magnetism on solenoid coil top.
cool
	Solenoid coil circuit is open.	Check coil resistance. If MΩ range, replace
		solenoid coil.
	Modulating valve is not operating, but OUT2 LED is on.	Set process temperature to minimum and
		check for complete travel of valve.
	Insufficient pressure differential between cooling	Find a means to get less back pressure in
	WATER IN and OUT lines.	the WATER OUT line.
	Cooling valve is undersize.	Replace cooling valve with a larger valve.
	Defective heater contactor.	Visually inspect coil and contacts;
		repair/replace defective contactors.
		Check resistance on all three (3) legs of the
Unit does not heat/cannot	Defective immersion heater.	heater with an ohm meter. If not all equal,
		contact factory for replacement heater.
achieve set point
	Heater contactor is not energizing, but HEAT LED is on.	Set process temperature to maximum and
		check for control voltage at heater contactor.
	Faulty/dirty solenoid valve.	Press VENT button several times to flush
		the valve.
Sterling, Inc.		Part No: 682.92594.10
2900 S. 160th Street · New Berlin, WI 53151 · USA		Bulletin No: HC2-320

Tel. 262.641.8610 • Fax 262.641.8653