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Problem
Induced draft blower runs
continuously with no
further furnace operation.
Integrated control module
diagnostic LED is flashing
3 flashes.
Circulator blower runs
continuously. No furnace
operation.
Integrated control module
diagnostic LED is flashing
4 flashes.
Induced draft blower and
circulator blower runs
continuously. No furnace
operation.
Integrated control module
diagnostic LED is flashing
5 flashes.
Furnace fails to operate.
Integrated control module
diagnostic LED is flashing
6 flashes.
Normal furnace operation.
Integrated control module
diagnostic LED is flashing
7 flashes.
Furnace not operating.
Integrated control module
diagnostic LED is flashing
8 flashes.
Induced draft blower runs
continuously. Furnace
fails to operate.
Integrated control module
diagnostic LED is flashing
continuously.
40
LED Code
Fault/Cause
3 flashes
Pressure switch circuit not closed.
Induced draft blower is operating.
Pressure switch hose blocked, pinched
or connected improperly.
Blocked flue and/or inlet air pipe,
blocked drain system or weak induced
draft blower.
Incorrect pressure switch setpoint or
malfunctioning switch contacts.
Loose or improperly connected wiring.
4 flashes
Primary or auxiliary limit circuit is open
or faulty.
Insufficient conditioned air over the
heat exchanger. Blocked filters,
restrictive ductwork, improper
circulator blower speed or failed
circulator blower.
Loose or improperly connected wiring.
5 flashes
Flame sensed with no call for heat.
Short to ground in flame sensor circuit.
6 flashes
Rollout limit switch open.
Integrated control module fuse is
blown.
Flame rollout.
Misaligned burners, blocked flue
and/or air inlet pipe or failed induced
draft blower.
Loose or improperly connected wiring.
Short in 24-volt AC control circuits or
safety circuits.
Faulty rollout limit switch.
7 flashes
Flame sensor microamp signal is low.
Flame sensor is coated/oxidized.
Flame sensor incorrectly positioned in
burner flame.
Lazy burner flame due to improper gas
pressure or combustion air.
8 flashes
Problem with igniter circuit. Improperly
connected igniter. Bad igniter.
Poor unit ground.
Poor burner ground.
Faulty integrated control module.
Continuous
Polarity of 115-volt or 24-volt power is
flashes
reversed.
Polarity of 115-volt AC power to
furnace or integrated control module is
reversed.
Red and blue wires to transformer are
reversed.
Poor unit ground.
Solution
Inspect pressure switch hose. Repair, if
necessary,
Inspect flue and/or inlet air piping for
blockage, proper length, elbows, and
termination. Check drain system. Correct
as necessary.
Correct pressure switch setpoint or
contact motion.
Tighten or correct wiring connection.
Check primary limit switch. Replace, if
necessary.
Check filters and ductwork for blockage.
Clean filters or remove obstruction.
Check circulator blower speed and
performance. Correct speed or replace
blower if necessary.
Tighten or correct wiring connection.
Correct short at flame sensor or in flame
sensor wiring.
Check burners for proper alignment.
Check flue and air inlet piping for
blockage, proper length, elbows and
termination. Correct as necessary. See
"Vent/Flue Pipe."
Check rollout limit switch. Replace, if
necessary.
Check induced draft blower for proper
performance. Replace, if necessary.
Tighten or correct wiring connection.
Repair short in 24-volt AC control/safety
circuit(s).
Replace integrated control module fuse
(3A).
Sand flame sensor with emery cloth.
Inspect for proper sensor alignment.
Compare current gas pressure to rating
plate info. Adjust as needed.
Check and correct wiring from integrated
control module to igniter
Replace bad igniter.
Check and correct unit ground wiring.
Replace bad integrated control module.
Review wiring diagram to correct polarity.
Verify proper ground. Correct if
necessary.
Reverse red and blue wires connected to
transformer.
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