Service Manual

TROUBLESHOOTING
49
Symptoms of Abnormal
Operation (Legacy
& ComfortNet™
Thermostat)
Diagnostic/
Status LED
Codes
Fault Description
ComfortNet™
Thermostat Only
Possible Causes Corrective Actions Notes & Cautions
Message Code
• Furnace fails to operate.
• Integrated control
module LED display
provides E7 error code.
•ComfortNet™
thermostat “Call
for Service” icon
illuminated.
•ComfortNet™
thermostat scrolls
“Check Furnace”
message.
E7 • Problem with
igniter circuit.
IGNITER
FA ULT
E7 • Improperly connected
igniter.
• Shorted igniter.
• Poor unit ground.
• Igniter relay fault on
integrated control
module.
• Check and correct
wiring from integrated
control module to
igniter.
• Replace shorted igniter.
• Check and correct unit
ground wiring.
• Check igniter output
from control. Replace if
necessary.
• Turn power OFF
prior to repair.
• Replace igniter with
correct replacement
part.
• Replace control with
correct replacement
part.
• Furnace fails to operate
on high stage; furnace
operates normally on low
stage.
• Integrated control module
LED display provides E8
error code.
E8 • High stage
pressure switch
circuit is closed
at start of heating
cycle.
• Induced draft
blower is
operating.
• Furnace is
operating on low
stage only
PS2 CLOSED E8 • High stage pressure
switch contacts sticking.
• Shorts in pressure
switch circuit wiring.
• Replace high stage
pressure switch.
• Repair short in wiring
• Turn power OFF prior
to repair.
• Replace pressure
switch with proper
replacement part.
• Furnace fails to operate
on high stage; furnace
operates normally on low
stage.
• Integrated control module
LED display provides E9
error code.
E9 • High stage
pressure switch
circuit is not
closed.
• Induced draft
blower is
operating.
• Furnace is
operating on low
stage only
PS2 OPEN E9 • 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.
• Furnace fails to operate.
• Integrated control module
LED display provides EA
error code.
• ComfortNet™ thermostat
“Call for Service” icon
illuminated.
• ComfortNet™ thermostat
scrolls “Check Furnace”
message.
EA • Polarity of 115 volt
AC is reversed
REVERSED
PLTY
EA • Polarity of 115 volt AC
power to furnace or
integrated module is
revered.
• Poor unit ground
• Review wiring diagram to
correct polarity.
• Verify proper ground.
Correct if necessary.
• Check and correct
wiring.
• Turn power OFF prior
to repair.
• Integrated control
module LED display EF
error code.
• ComfortNet™ thermostat
“Call for Service” .
EF • Aux switch open Aux Alarm
Fault
EF • High water level in the
evaporation coil.
• Check overfow pan and
service.
• Turn power OFF prior
to service.
• Furnace fails to operate.
• Integrated control module
LED display provides d0
error code.
• ComfortNet™ thermostat
“Call for Service” icon
illuminated.
• ComfortNet™ thermostat
scrolls “Check Furnace”
message.
d0 • Data not yet on
network.
NO NET
DATA
d0 • Furnace does not
contain any shared data.
• Populate shared data
set using memory card.
• Turn power OFF prior
to repair
• Use memory card for
the specifc model.
• Insert memory card
BEFORE turning
power ON. Memory
card may be removed
after data is loaded
and power is turned
off.
• Error code will be
cleared once data is