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PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE
Condition Possible Cause Corrective Action / Comments
1.5
– On initial power–up the combus-
tion air blower remains energized.
1.5.1
Improper ground to the unit.
ACTION 1 – Check that the unit is properly
ground.
ACTION 2 – Install a proper main ground to the
unit
– Diagnostic lights
lash the im-
proper main ground.
1.5.2
6–Pin connector is improperly at-
tached to the circuit board.
ACTION 1 – Check 6–pin connector for proper
installation. Correctly insert connector into
control.
LED#1–Alternating Fast Flash
LED#2–Alternating Fast Flash
1.5.3
Line voltage is below 75V.
ACTION 1 – Check that the line voltage is
above 75V. Determine cause of voltage drop
and supply correct voltage to the control.
PROBLEM 2: UNIT FAILS TO OPERATE IN THE COOLING OR HEATING MODE, BUT COMBUSTION
AIR BLOWER OPERATES CONTINUOUS. UNITS WITH CONTROL BOARDS DATE CODED AFTER
NOV. 1 1997, WILL OPERATE IN COOLING BUT NOT IN THE HEATING MODE, WITH COMBUSTION
AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF.
Condition Possible Cause Corrective Action / Comments
2.1
– On initial power–up the combus-
tion air blower remains energized.
– Diagnostic lights flash the im-
proper main ground.
– Units with control boards date
2.1.1
Open ignitor circuit.
ACTION 1 – Check for correct wiring and loose
connections in the ignitor circuit. Check mult–
plug connections for correct installation.
coded after Nov.1 1997; combus-
tion air blower will cycle 5 seconds
on 55 seconds off.
LED#1–Alternating Fast Flash
LED#2–Alternating Fast Flash
2.1.2
Broken or failed ignitor.
ACTION 1 – Unplug ignitor and read resis-
tance across ignitor. If resistance does not
read between 10.9 and 19.7 ohms, replace the
ignitor.
PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT
ENERGIZE
Condition Possible Cause Corrective Action / Comments
3.1
– Unit operates with a cooling or
continuous fan demand.
– Combustion air blower will not
start with a Heating demand.
– Diagnostic lights flash the limit fail-
3.1.1
Primary or secondary (if equipped )
limit open.
ACTION 1 – Check continuity across
switch(es). Switches reset automatically upon
cool down.
ACTION 2 – Check for restrictions on blower
inlet air (including filter) and outlet air. Deter-
mine cause for limit activation before placing
unit back in operation.
.
LED#1–Slow Flash,
LED#2–On
3.1.2
Miswiring of furnace or improper
connections at limit switch(es).
ACTION 1 – Check for correct wiring and loose
connections. Correct wiring and/or replace
any loose connections.
3.2
– Unit operates with a cooling and
continuous fan demand.
– Combustion air blower will not
start with a Heating demand.
– Diagnostic lights flash the pres-
3.2.1
Miswiring of furnace or improper
connections to combustion air
blower.
ACTION 1 – Check for correct wiring and loose
connections. Correct wiring and/or replace
any loose connections.
sure sw
c
a
ure co
e.
LED#1–Off,
LED#2–Slow Flash
3.2.2
Pressure switch stuck closed.
ACTION 1 – Check that the pressure switch is
open without the combustion air blower oper-
ating. Replace if defective.
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