General Troubleshooting Guide - McQuay MWM Service Manual

MCQUAY Service Guide Book

7.5 General Troubleshooting Guide

By means of pressure readings:
Pressure
Data
Circuit
High Side
Low Side
High Side
Low Side
High Side
Low Side
High Side
Low Side
High Side
Low Side
Probable Cause
1. Overcharged with refrigerant.
2. Non-condensable gases in refrigerant
circuit (eg. Oil)
3. Obstructed air-intake / discharge.
4. Short circuit of hot air at condensing unit.
1. Poor compression / no compression
(compressor defective).
2. Check valve stick in open position.
3. Reversing valve leaking (for heatpump
only).
1. Undercharged with refrigerant.
2. Refrigerant leakage.
3. Air filter clogged / dirty (indoor unit).
4. Indoor fan locked (cooling).
5. Defective defrosts control, outdoor coil
freeze up (heating).
6. Outdoor fan locked (heating).
1. Outdoor fan blocked (cooling).
2. Outdoor coil dirty (cooling).
3. Indoor fan locked (heating).
4. Indoor filter clogged dirty (heating).
1. Air intake temperature of indoor unit too
high.
76
Diagnosis