Lennox MMDB User Guide

7
Error Codes
Indoor units are equipped with either a small panel
with four LEDs that ash to indicate system errors or a
digital display that provides an error code. Refer to the
appropriate table below to view the error codes. If the
unit has a digital display, the error code will replace the
temperature setting displayed on the front cover of the
indoor unit. If more than one error has occurred, the codes
will alternate so that all codes are shown. Make note of the
code (E1, EE, etc.), then reset the display by pressing the
ON/OFF button on the wireless remote controller. Press
the ON/OFF button a second time to reapply power to
system. If code is still displayed, discon nect and restore
power at the unit disconnect switch or circuit breaker. If
the problem was temporary, the code will not reappear.
If the error code reappears after power has been broken
and restored at the disconnect switch or circuit breaker,
call a licensed professional HVAC service technician.
Table 2. MWMA, MWMB and 3WMB
Troubleshooting Codes
Code Description
E0 Indoor unit EEPROM error
E1 Communication error between indoor unit and outdoor unit
E3 Indoor fan speed error
E4 Indoor return air temperature sensor error
E5 Indoor coil temperature sensor error
EC Low refrigerant
EE High water level alarm
F0 Outdoor current overload sensed
F1 Outdoor ambient temperature sensor error
F2 Outdoor coil temperature sensor error
F3 Compressor discharge temperature sensor error
F4 Outdoor unit EEPROM error
F5 Outdoor unit fan speed error
P0 Inverter module IPM error
P1 High or low voltage protection
P3 Outdoor unit low temperature lockout
P4 Compressor drive error
-- Mode conict
P6 Compressor high-pressure or low-pressure switch open
Table 3. MCFA, MCFB, MMDA, MMDB, M22A M33A
and M33B Troubleshooting Codes
Display Description
E0 Indoor unit EEPROM error
E1 Communication error between indoor and outdoor units
(E2 for outdoor code)
E3 Indoor fan speed error
E4 Indoor return air temperature sensor error
E5 Indoor coil temperature sensor error
EC Low refrigerant
EE High water level alarm (for ducted units only)
F0 Outdoor current overload sensed Note: (outdoor unit
display --) two dashes
F1 Outdoor ambient temperature sensor error (T4
malfunction) outdoor unit display E4
F2 Outdoor coil temperature sensor error (T3) Malfunction
outdoor unit display E4
F3 Compressor discharge temperature sensor error (T5)
Malfunction outdoor unit display E4
F4 Outdoor unit EEPROM error - outdoor display E0
F5 Outdoor unit fan speed error - outdoor Error display E8
P0 Inverter module IPM error - outdoor display P6
P1 High or low voltage protection - outdoor display E5
P3 Outdoor unit low temperature lockout - outdoor unit
display LP
P4 Compressor drive error
P6 Mode conict
P7 Compressor high- or low-pressure switch open - outdoor
unit display P2

Lennox MMDB Specifications

General

Brand	Lennox
Model	MMDB
Category	Air Conditioner
Language	English