507607-03
Issue 1827
Page 17 of 23
Code
Diagnostic Codes / Status of Equipment
Action Required to Clear and Recover
E420
The heat pump defrost cycle has taken more than 20
minutes to complete.
Defrost cycle lasts longer than 20 minutes. This alarm is
applicable with non-communicating heat pump system only.
Check heat pump defrost operation. The alarm is cleared after
the “W1” signal is removed.
E421
The W output terminal on the outdoor unit is not wired
correctly.
Voltage sensed on W and O when Y1 thermostat input is
deactivated. Another device or wiring fault is energizing W
check wiring. The alarm clears when wiring is corrected or
after a power reset.
NOTE
:
Additional codes may be found in the Comfort Sync room thermostat manual.
Table 5. 7-Segment Alert and System Status Codes
Mode
Description
Example of Display
Power Up / Reset
Unit type and number of stages is
displayed. Verify configuration with
information published on the unit
nameplate. If the information is
incorrect, refer to flow chart “Manual
Configuration of Unit Type” to
reconfigure control.
1 Stage AC: 1AC
2 Stage AC: 2AC
1 Stage AC: 1HP
1 Stage AC: 2HP
Power-Up 7-Segment Display String
2
H
P
___
___
___
___
___
___
Unit Type / Stages
No Capacity
No Fan Profile
Power Up / Reset
following display
of self-discovered
configuration
Unit nominal capacity is displayed. If
not programmed, then three horizontal
lines and the decimal point are
displayed for 2 seconds.
Power up nominal capacity display of an 4SHP - LS136
Power-Up 7-Segment Display String
2
H
P
3
6
___
___
___
Unit Type / Stages
Capacity
No Fan Profile
Power Up / Reset
following display
of nominal
capacity
Fan Profile code (a single- or two-digit
number).
Displays the number of the selected fan profile.
Power-Up 7-Segment Display String
2
H
P
3
6
3
Unit Type / Stages
Capacity
Fan Profile
Idle Mode
Decimal point blinks at 1 Hz
Idle Mode: Decimal point blinks at 1 Hz (0.5 second on, 0.5 second
off). Display OFF.
Soft Disabled
Top and bottom horizontal line and
decimal point blink at 1 Hz.
Soft Disabled: Top and bottom horizontal line and decimal point blink
at 1 Hz (0.5 second on, 0.5 second off).
NOTE
: Control should be
replaced.
O.E.M. Test Mode
All segments flashing at 2 Hz (unless error is detected).
NOTE
: Control
should be replaced.
*Information will be displayed, but does not apply to this unit.
Table 6. Outdoor Control 7-Segment Unit Status Displays
