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Micro Series Water Temperature Control Units
Reference Manual (PN: 682.89373.00) for
Complete Operation and Installation Instructions
(Available online at www.sterlco.com)
Sterling, Inc. Part No: 682.92594.10
2900 S. 160
th
Street · New Berlin, WI 53151 · USA Bulletin No: HC2-320
Tel. 262.641.8610 • Fax 262.641.8653
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
nameplate rating.
Defective on/off switch. Replace.
Control circuit fuse blown. Replace.
Unit does not turn on
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.
Low water pressure light on.
Check for at least 16 psig (110.32 kPa/1.1
bars) water pressure on WATER IN or CITY
WATER MAKEUP.
Water supply to unit is turned off. Open water supply.
Unit does not run
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.
Serpentine flow through mold.
Connect lines for parallel flow instead of
series flow.
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.
Temperature fluctuations/
rapid cycling from hot to
cold.
Lime buildup in unit piping. Clean or replace.
Drain is plugged or excessive back pressure is in drain
line.
Clear drain line or eliminate back pressure
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.
Solenoid valve is not operating, but COOL LED is on.
Set process temperature to minimum and
check for magnetism on solenoid coil top.
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
WATER IN and OUT lines.
Find a means to get less back pressure in
the WATER OUT line.
Unit overheats or does not
cool
Cooling valve is undersize. Replace cooling valve with a larger valve.
Defective heater contactor.
Visually inspect coil and contacts;
repair/replace defective contactors.
Defective immersion heater.
Check resistance on all three (3) legs of the
heater with an ohm meter. If not all equal,
contact factory for replacement heater.
Heater contactor is not energizing, but HEAT LED is on.
Set process temperature to maximum and
check for control voltage at heater contactor.
Unit does not heat/cannot
achieve set point
Faulty/dirty solenoid valve.
Press VENT button several times to flush
the valve.