Problem Possible Causes Corrective Action
The furnace does not heat No power. Check power source and fuses or
(CYCLE light does not illuminate). breakers.
Defective electrical hookup. Repair electrical hookup.
Thermocouple has oxidized and Replace thermocouple.
opened the circuit. (Open thermocouple
is indicated on the display as a
temperature of 0-5 degrees).
Fuse(s) blown Replace fuse(s).
Controller malfunction. Replace controller.
Door switches malfunction. Re-align or replace door safety switches.
Defective solid state relay. Replace output relay.
Power is not cut to heating elements Door switches are not functioning Re-align or replace door switches.
when the door is open.
Slow heatup. Low line voltage. Install line of sufficient size and proper
voltage. (Isolate furnace from other
electrical loads.)
Heavy load in chamber. Lighten load in chamber.
Wrong heating element. Install proper element.
Repeated element burnout. Overheating furnace. Keep furnace under maximum
temperature.
Heating harmful materials. Enclose material in container. Clean up
spills in and on chamber. Ventilate
chamber by opening door slightly when
heating known harmful reagents.
Contamination present from Replace insulation material.
pervious burnout.
Inaccurate temperature Oxidized or contaminated Replace thermocouple.
readout. thermocouple.
Poor thermocouple connection. Tighten connections.
Improper loading procedures. Use proper loading procedures.
Poor ventilation of base. Clear area around furnace base.
Thermocouple connections Reconnect thermocouple correctly.
reversed. (Indicated by
downscaling of temperature on
display.)
Controller malfunction. Replace controller.
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