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K. Power On Check
When AC power is first applied, all segments of display are turned
on for a few seconds. Following this, temperature display indicates
model/configuration via following 2-digit code:
AC—1-speed air conditioner, HP—1-speed heat pump, A2—2-
speed air conditioner, H2—2-speed heat pump, HS—1-speed heat
pump with 3-stage auxiliary heat, dF—dual fuel, d2—dual fuel
with 2-speed.
L. Error Codes
-- — If Thermidistat Control cannot properly read room tempera-
ture, display will indicate -- and all outputs (except fan if
on) will turn off.
E1, E2 — There is no E1 or E2 error message.
E3 — If Thermidistat Control cannot properly read outdoor
temperature, and it is needed for proper operation, display
will indicate E3.
SYMPTOM
No display
"--" in place of room temperature
"E3" or "--" in place of outdoor temperature
"E4" or "E5"
"E6"
"Clean Filter" icon displayed
Cooling or heating will not come on
Humidify or dehumidify will not come on
THERMIDISTAT CONTROL TROUBLESHOOTING
Open Thermidistat Control. Check for 24vac between R and C at screw terminals on mounting base. Re-
assemble, making sure pins on board engage sockets in mounting base. If display does not appear, re-
place Thermidistat Control.
Thermidistat Control cannot properly read room temperature. Replace Thermidistat Control.
Thermidistat Control cannot properly read outdoor temperature. Check outdoor sensor and its wiring.
Internal failure. Replace Thermidistat Control.
System is stuck in defrost. Check wiring and heat pump defrost control board.
Filter timer has expired. Clean or replace filter and then press VACATION and HOLD/END buttons to-
gether to reset.
See Installer Setup to force heating or cooling. Check for 24vac at equipment terminals. If not present,
check wiring.
See Installer Setup to force HUM or DEHUM. Check for 24vac at equipment terminals. If not present,
check wiring.
—19—
E4 — If Thermidistat Control's internal memory fails, E4 will be
displayed. Replace Thermidistat Control.
E5 — If Thermidistat Control cannot properly read humidity, E5
will be displayed. Replace Thermidistat Control. E6 — If
defrost cycle continues for longer than 15 minutes. E6 will be
displayed. Check heat pump wiring or for failed heat pump defrost
control.
M. Smart Recovery
With Smart Recovery selected, transition out of setback begins a
fixed time period before selected recovery time and gradually
adjusts room temperature so desired temperature will be achieved
at selected recovery time. The fixed time period is 1.5 hr. It
operates in both heating and cooling. This only applies to
programmable operation.
WHAT TO CHECK
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