General Troubleshooting Guide - McQuay MWM Service Manual Book

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 defrost 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.
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