Lennox MLA018S4S-1P

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MINI-SPLIT SYSTEMS SERVICE MANUAL

CORP1602-L9

3/2017

Supersedes 10/2016

WARNING

Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss

of life.

Installation and service must be performed by a licensed professional HVAC installer (or equivalent) or service agency

Main Page

Default Chapter2
- Table of Contents2
1 Single and Multiple Zone Outdoor Units5
- Model Number Identification5
- MPA Single-Zone Specifications Outdoor Units (0.75 - 1.5 Ton)6
- MPA Single-Zone Specifications Outdoor Units (2.0 - 4.0 Ton)7
- MPB Single-Zone Specifications Outdoor Units (0.75 - 1.5 Ton)8
- MPB Single-Zone Specifications Outdoor Units (2 - 4 Ton)9
- MLA Single-Zone Specifications Outdoor Units (0.75 - 2 Ton)10
- MPA Multi-Zone Specifications Outdoor Units (1.5 - 2.5 Ton)11
- MPA Multi-Zone Specifications Outdoor Units (3 - 4 Ton)12
- MPB Multi-Zone Specifications Outdoor Units (1.5 - 2.5 Ton)13
- Mpb Multi-Zone Specifications Outdoor Units (3 - 4 Ton)14
- MLA Multi-Zone Specifications Outdoor Units (1.5 - 3 Ton)15
- Single-Zone Outdoor Unit Dimensions16
- Multi-Zone Outdoor Unit Dimensions17
- Outdoor Unit Clearances18
2 M22A, M33A and M33B Cassette Non-Ducted Indoor Units19
- Model Number Identification19
- M22A Indoor Unit Specifications19
- M33A and M33B Indoor Unit Specifications20
- M22A Indoor Unit Dimensions21
- M33A and M33B Indoor Unit Dimensions22
- M22A, M33A and M33B Indoor Unit Clearances23
3 MMDA Ducted Indoor Units24
- Model Number Identification24
- Indoor Unit Specifications24
- Indoor Unit Blower Data25
- Indoor Unit Dimensions28
- Indoor Unit Clearances29
4 MWMA and MWMB Wall Mounted Indoor Units30
- Model Number Identification30
- Indoor Unit Specifications (009 - 012 Ton) Units30
- Indoor Unit Specifications (018 - 030 Ton) Units30
- Indoor Unit Dimensions31
- Indoor Unit Clearances31
5 MCFA and MCFB Ceiling / Floor Indoor Units32
- Model Number Identification32
- Indoor Unit Specifications (018 - 048 Ton) Units32
- Indoor Unit Dimensions33
- Indoor Unit Clearances34
6 Indoor / Outdoor Unit Combinations35
- MPA Multi-Zone System Combinations35
- MPB Multi-Zone System Combinations37
- MLA Multi-Zone System Combinations40
7 Refrigeration Pipe Work41
- MPA and MPB Single-Zone Refrigerant Cycle Diagram41
- MPA and MPB Two-Zone Refrigerant Cycle Diagram41
- MPA and MPB Three-Zone Refrigerant Cycle Diagram42
- MPA and MPB Four-Zone Refrigerant Cycle Diagram42
- MPA and MPB Five-Zone Refrigerant Cycle Diagram43
- Single-Zone Piping Limitations44
- Multi-Zone Piping Limitations44
8 Master Valves (3- to 5-Zone Outdoor Units)46
9 MPA, MPB and MLA Outdoor Unit Connections and Line Set Usage47
10 Power Wiring for Outdoor and Indoor Units (Diagrams)52
11 Outdoor Unit Diagrams55
- MPA and MPB Single-Zone55
- MLA Single-Zone61
- MPA and MPB Multi-Zone62
- MLA Multi-Zone66
12 Indoor Unit Diagrams68
- Mwma And Mwmb Indoor Unit68
- M22A Indoor Unit68
- M33A And M33B Indoor Unit69
- Mmda Indoor Units70
- Mcfa And Mcfb Indoor Units72
13 Control Board Photos75
14 Condensate Pipe Work Installation77
- Outdoor Unit Condensate Piping77
- Indoor Unit Gravity Drain78
- Indoor Unit Lift Pump79
15 Controls82
- M0STAT60Q-1 Wireless Remote82
- M0STAT61Q-1 Wired Remote85
16 Connection to Centralized Controller87
- Set Indoor Unit Address For Centralized Control87
- Indoor Unit Connection Points For Centralized Controller88
17 Indoor Unit Connection Points for ON/OFF Device88
18 Indoor Unit Connection Points for Alarm Device89
19 Start-Up90
- Adding Refrigerant - Single-Zone Systems90
- Adding Refrigerant - Multi-Zone Systems90
- Outdoor Unit Spot Check Function91
- Outdoor Unit Digital Display Tube93
- Dry Mode Operation - Mwma And Mwmb93
- Test Run - Mwda And Mwmb93
- Double-Check Pipe Connections94
- Ambient Temperature Is Below 63°F (17°C)94
20 Quick Reference Guide - Error Codes95
21 Single-Zone Outdoor Unit LED Locations97
22 Multi-Zone Outdoor Unit Leds and SW1 Locations101
23 Troubleshooting Outdoor Unit Error Codes102
24 Indoor Unit Indicators and Controls126
- Cassette Unit Display126
- Ducted Unit Display126
- Wall-Mounted And Ceiling/Floor Unit Displays127
25 Troubleshooting Indoor Unit Error Codes128
26 Temperature Sensor Resistance Values152
27 Discharge Temperature Sensor Resistance Values153
28 Temperature Sensor Identification Table154
29 Component Troubleshooting154
- Compressor Check154
- Ipm Check155
- Ac Fan Motor156
- Four-Way Valve157
- Exv Check158
30 Component Protection159
- Fan Motor159
- Inverter Module Protection159
- Low Voltage Protection159
- Compressor Current Limit Protection159
31 Specifications And Operations160
- Capacity Request Calculations161
- Heating Mode162
- Defrost Control163
- Defrost Theory163
- Defrost Termination164
- Outdoor Fan Control164
- Four-Way Valve Control165
- Electronic Expansion Valve (EXV) Control166
32 Index167

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Questions and Answers:

B
Brent JohnsonAug 6, 2025
What to do if my Lennox MLA018S4S-1P Air Conditioner shows an outdoor EEPROM malfunction?
- D
  David FletcherAug 6, 2025
  If your Lennox Air Conditioner displays an outdoor EEPROM malfunction, try these steps: * Power off the unit, then restart it after 3 minutes. * If the issue persists, the outdoor main PCB may need to be replaced.