Service Manual

TROUBLESHOOTING
48
Symptoms of Abnormal
Operation (Legacy
& ComfortNet™
Thermostat)
Diagnostic/
Status LED
Codes
Fault Description
ComfortNet™
Thermostat Only
Possible Causes Corrective Actions Notes & Cautions
Message Code
• Induced draft blower
runs continuously with no
further furnace operation.
• Integrated control module
LED display provides E2
error code.
• ComfortNet™ thermostat
“Call for Service” icon
illuminated.
• ComfortNet™ thermostat
scrolls “Check Furnace”
message.
E2 • Low stage
pressure switch
circuit is not
closed.
PS1 OPEN E2 • Pressure switch hose
blocked pinched, or
connected improperly.
• Blocked fue and/or inlet
air pipe, blocked drain
system or weak induced
draft blower.
• Incorrect pressure
switch set point or
malfunctioning switch
contacts.
• Loose or improperly
connected wiring.
• Inspect pressure switch
hose. Repair/replace if
necessary.
• Inspect fue and/or inlet
air piping for blockage,
proper length, elbows,
and termination. Check
drain system. Correct as
necessary.
• Check induced draft
blower performance.
Correct as necessary.
• Correct pressure switch
set point or contact
motion.
• Tighten or correct wiring
connection.
• Turn power OFF prior
to repair.
• Replace pressure
switch with proper
replacement part.
• Replace induced draft
blower with proper
replacement part.
• Circulator blower
runs continuously. No
furnace operation.
• Integrated control
module LED display
provides E3 error code.
•ComfortNet™
thermostat “Call
for Service” icon
illuminated.
•ComfortNet™
thermostat scrolls
“Check Furnace”
message.
E3 • Primary limit or
auxiliary limit
circuit is open.
• Rollout limit
circuit is open.
HIGH LIMIT
OPEN
E3 • Insuffcient conditioned
air over the heat
exchanger. Blocked
flters, restrictive
ductwork, improper
circulator blower
speed, or failed
circulator blower motor.
• Flame rollout.
• Misaligned burners,
blocked fue and/or
air inlet pipe, or failed
induced draft blower.
• Loose or improperly
connected wiring.
• Check filters and
ductwork for blockage.
Clean flters or remove
obstruction.
• Check circulator
blower speed and
performance. Correct
speed or replace blower
motor if necessary.
•Check burners for
proper alignment.
• Check fue and air inlet
piping for blockage,
proper length, elbows,
and termination.
Correct as necessary.
• Check induced draft
blower for proper
performance. Replace if
necessary.
• Tighten or correct
Wiring connection.
• Turn power OFF
prior to repair.
• See Specifcation
Sheet applicable
to your model* for
allowable rise range
and proper circulator
speed.
• See "Vent/Flue Pipe"
section for piping
details.
• Induced draft blower
and circulator blower
runs continuously. No
furnace operation.
• Integrated control
module LED display
provides E4 error code.
•ComfortNet™
thermostat “Call
for Service” icon
illuminated.
•ComfortNet™
thermostat scrolls
“Check Furnace”
message.
E4 • Flame sensed
with no call for
heat.
IMPROPER
FLAME
E4 • Short to ground in
Flame sense circuit.
• Lingering burner fame.
• Slow closing gas valve.
• Correct short at flame
sensor or in flame
sensor wiring.
• Check for lingering
flame.
• Verify proper operation
of gas valve.
• Turn power OFF
prior to repair.
• No furnace operation.
• Integrated control
module LED display
provides E5 error code.
•ComfortNet™
thermostat displays
“Battery Power”
E5 • Open Fuse Not
Displayed
Not
Displayed
• Short in low voltage
wiring
• Locate and correct
short in low voltage
wiring
• Turn power OFF
prior to repair.
• Replace fuse with
3-amp automotive
type
• Normal furnace
operation.
• Integrated control
module LED display
provides E6 error code.
E6 • Flame sense
micro amp signal
is low
WEAK
FLAME
E6 • Flame sensor is
coated/oxidized.
•Flame sensor
incorrectly positioned
in burner fame.
• Lazy burner flame
due to improper gas
pressure or combustion
air.
• Clean flame sensor if
coated/oxidized.
• Inspect for proper
sensor alignment.
• Check inlet air piping
for blockage, proper
length, elbows, and
termination.
• Compare current gas
pressure to rating plate.
Adjust as needed.
• Turn power OFF
prior to repair.
• Clean fame sensor
• See "Vent/Flue Pipe"
section for piping
details.
• See rating plate for
proper gas pressure.