Daikin FDMQ18RVJU Service Manual

299 pages

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[Applied Models]



Inverter Pair : Heat Pump

Multi-Split Type Air Conditioners

5MXS-T, 4MXL-T Series

Service

Manual

SiUS121827E

Table of Contents

Other manuals for Daikin FDMQ18RVJU

Installation Manual22 pages

Manual152 pages

Operation Manual12 pages

Questions and Answers:

J
Jimmy WilsonAug 14, 2025
What to do if the operation lamp is blinking on my Daikin FDMQ18RVJU?
- J
  Joshua KnightAug 14, 2025
  If the operation lamp on your Daikin Air Conditioner is blinking, you should first perform the diagnostic procedure. Also, ensure all indoor units connected to a multi-system outdoor unit are set to the same operation mode. If they aren't, set all indoor units to the same operation mode and check if the operation lamp stops blinking. You can also try setting all indoor units to cooling or heating mode to see if the operation lamp returns to normal.
C
Craig MooreAug 18, 2025
Why is my Daikin FDMQ18RVJU cooling effect poor?
- M
  Michael BrownAug 18, 2025
  If your Daikin Air Conditioner isn't cooling or heating effectively, try these steps: * Ensure the air filters are clean. * Check for and remove any obstructions blocking the air inlet or outlet of both the indoor and outdoor units. * Verify that the temperature setting is appropriate for your needs. * Make sure all windows and doors are properly closed. * Confirm that the air flow rate and direction are set correctly.
J
Jennifer BrownAug 21, 2025
Why Daikin Air Conditioner does not operate?
- A
  Aaron NewmanAug 21, 2025
  If your Daikin Air Conditioner isn't operating and the OPERATION lamp is off, check the following: * Ensure the circuit breaker hasn’t been turned OFF or a fuse hasn't blown. Check the circuit breaker. * Confirm there isn’t a power failure. * Verify that batteries are correctly installed in the remote controller. Install batteries if needed. * Check the timer setting to ensure it is correct.
J
Jeffrey PerezAug 25, 2025
How to fix Daikin FDMQ18RVJU Air Conditioner if operation does not start soon?
- D
  danielshollyAug 25, 2025
  If your Daikin Air Conditioner operation does not start soon after pressing the ON/OFF button or reselecting the mode, you should wait for about 3 minutes.
R
robertwalkerAug 28, 2025
What to do if Daikin FDMQ18RVJU Air Conditioner operation stops suddenly?
- M
  Martin RichAug 28, 2025
  If the Daikin Air Conditioner operation stops suddenly and the OPERATION lamp is flashing, it could be due to: * Dirty air filters, so clean them. * Obstructions blocking the air inlet or outlet of the indoor or outdoor units, so remove any obstacles. * Inconsistent operation modes for indoor units connected to outdoor units in a multi system, so set all indoor units to the same operation mode.
R
Robin DavidsonAug 31, 2025
Why HEAT operation stops suddenly in Daikin FDMQ18RVJU Air Conditioner?
- C
  Claire SchwartzAug 31, 2025
  If the HEAT operation on your Daikin Air Conditioner stops suddenly and you hear a flowing sound, the system is likely removing frost from the outdoor unit. Please wait for approximately 4 to 12 minutes.
R
Robert TrujilloSep 3, 2025
What to do if Daikin Air Conditioner operation stopped suddenly?
- M
  Melody NewtonSep 4, 2025
  If the Daikin Air Conditioner operation stopped suddenly (OPERATION lamp is on), it might be due to a sudden large voltage fluctuation. The system is designed to protect itself and will automatically resume operation in about 3 minutes.
C
Carolyn GonzalezSep 7, 2025
Why does no air come out of my Daikin FDMQ18RVJU Air Conditioner?
- M
  michelle38Sep 7, 2025
  If your Daikin Air Conditioner isn't emitting air, especially during HEAT operation or defrosting, allow 1 to 4 minutes for the air to start flowing. If the air conditioner operates immediately after the circuit breaker is turned on, allow 3 to 20 minutes.

Daikin FDMQ18RVJU Specifications

General

Brand	Daikin
Model	FDMQ18RVJU
Category	Air Conditioner
Language	English

Summary

Introduction

Safety Cautions

Essential safety precautions for workers and users, including warnings and icon explanations.

Part 2 Specifications

Specifications

Part 3 Printed Circuit Board Connector Wiring Diagram

Indoor Unit

Wiring diagrams and connector identification for various indoor unit models.

Outdoor Unit

Wiring diagram for the outdoor unit's main PCB.

Part 4 Functions and Control

Common Functions

RA Indoor Unit Functions

Details functions specific to RA indoor units, including airflow and fan speed control.

SA Indoor Unit Functions

Details functions specific to SA indoor units, including airflow and fan speed control.

Control Specification

Technical details on thermistor functions, mode hierarchy, and frequency control.

Part 5 Remote Controller

Part 6 Service Diagnosis

General Problem Symptoms and Check Items

Troubleshooting with LED

Diagnosing issues based on indoor and outdoor unit LED indicators.

Service Diagnosis

Detailed diagnostic procedures for remote controllers and system errors.

Code Indication on Remote Controller

Reference tables for error codes indicated on remote controllers.

Troubleshooting for RA Indoor Unit

Specific troubleshooting steps for RA indoor unit abnormalities.

Troubleshooting for SA Indoor Unit

Specific troubleshooting steps for SA indoor unit abnormalities.

Troubleshooting for Outdoor Unit

Specific troubleshooting steps for outdoor unit abnormalities and errors.

Check

Part 7 Trial Operation and Field Settings

Pump Down Operation

Forced Cooling Operation

Wiring Error Check Function

Trial Operation

Field Settings

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