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CTH3-SERIES INSTALLATION, OPERATION AND SERVICE MANUAL
60 of 71
12.1 Control LED
The control inside the heater's control compartment
is equipped with a tri-color LED. The LED offers
comprehensive diagnostic capability. The LED is
showing some form of status signal at all times when
the control is powered. The color of the LED
differentiates normal from error conditions as follows:
GREEN indicates normal operation.
RED indicates an error condition.
YELLOW (fast flashing) indicates a RETRY attempt.
LED NOT LIT indicates no power to control.
12.2 General LED Codes
No LED: No Power to control.
Slow Green: LED slowly flashes on and off,
indicates power to the control
board but no call for heat.
GREEN, 1 flash: Call for heat indicates the
heater is performing the safe
start pre-purge function or
H.S.I. warm-up.
GREEN, 2 flashes: Call for heat indicates the
heater is performing light off,
heater warm-up, or heater run.
GREEN, 3 flashes: *Only applicable for
thermostat control*
Gas ON - No call for heat, unit
modulating from single stage
thermostat.
AMBER, 1 flash: Call for heat when flame signal
is below 1µA
AMBER, 2 flashes: Gas ON - Call for heat when
flame signal is below 1µA
AMBER, 3 flashes: *Only applicable for
thermostat control*
Gas ON - No call for heat, unit
modulating from single stage
thermostat when flame signal
is below 1µA.
AMBER,
Fast Flashing: Heater is in RETRY mode.
RED Steady LED: Control FAILURE,
No 24 V power supply.
RED, 1 flash: Lockout- Insufficient sensed
air pressure when blower is
on.
Condition could be caused by:
• Air Side Door
• Blower
• Obstruction in
inlet or outlet
• Pressure hose fittings
• Pressure Switch
RED, 2 flashes: Lockout- Blower air pressure
reads above zero level when
blower is off.
Condition is caused by
a pressure sensor failure or
complete blockage of air
intake or exhaust vent.
RED, 3 flashes: Lockout- Flame is sensed on
when it should be off or off
when it should be on.
Could be caused by:
• Flame Rod
• H.S.I.
• Gas Supply
• 120 V Supply Polarity
• Board Fault
RED, 4 flashes: Locko
ut- Gas Valve.
Condition caused by main
valve on gas valve.
Check gas valve wiring.
RED, 5 flashes: Lockout- Board Failure.
Board must be replaced.
RED, 6 flashes: Not used.
RED, 7 flashes: Lockout- Fuse Open.
Condition could be caused by:
• Fuse blown
• High Limit Switch open a
board location J3