Carrier 38AUZ - User Manual

Questions and Answers

C
Christina BrooksAug 14, 2025
What to do if my Carrier 38AUZ Air Conditioner compressor is running but cooling is insufficient?
- R
  Robert ReynoldsAug 14, 2025
  If the Carrier Air Conditioner compressor is running but cooling is insufficient, it could be due to several reasons. These include low suction pressure or refrigerant charge (add refrigerant), low head pressure (check refrigerant charge and outdoor-air fan thermostat settings), dirty air filters (clean or replace filters), or a defective expansion valve power head (replace power head). Other possible causes are a partially iced indoor coil (check low-pressure setting), restricted indoor airflow (remove obstruction), high suction pressure (check unloader adjustments and setting), non-functioning unloaders (check unloader adjustments and setting), or excessive heat load (check for open doors or windows near the fan coil).
R
Randy PayneAug 25, 2025
Why is my Carrier 38AUZ Air Conditioner unit operating too long or continuously?
- C
  Carlos CarterAug 25, 2025
  If your Carrier Air Conditioner operates too long or continuously, it could be due to a low refrigerant charge (add refrigerant), fused control contacts (replace control), air in the system (purge and evacuate system), or a partially plugged expansion valve or filter drier (clean or replace).
P
perrymichelleAug 31, 2025
Why is my Carrier 38AUZ system noisy?
- C
  Christina ThompsonAug 31, 2025
  If the Carrier Air Conditioner system is noisy, it may be due to piping vibration (support piping as required) or a noisy compressor (replace compressor if bearings are worn).
M
Michael HaasSep 3, 2025
Why does my Carrier 38AUZ Air Conditioner compressor lose oil?
- M
  Mark OrozcoSep 3, 2025
  The Carrier Air Conditioner compressor may lose oil due to a leak in the system (repair leak), crankcase heaters not energized during shutdown (check wiring and relays, and replace heater if defective), or improper interconnecting piping design (check piping for oil return and replace if necessary).
A
Audrey GreenSep 6, 2025
Why is the liquid line hot in my Carrier 38AUZ?
- S
  summersbarrySep 6, 2025
  A hot liquid line in the Carrier Air Conditioner can be caused by a shortage of refrigerant due to a leak (repair leak and recharge) or an expansion valve that opens too wide (adjust expansion valve).
I
Isaac RandolphSep 9, 2025
What causes a frosted liquid line on a Carrier 38AUZ?
- J
  James BakerSep 10, 2025
  A frosted liquid line in the Carrier Air Conditioner can be caused by a restricted filter drier (remove restriction or replace) or a liquid line solenoid valve that is partially closed (replace valve).
V
Vicki MartinezNov 16, 2025
What to do if the Carrier Air Conditioner compressor does not run?
- L
  Lisa ChavezNov 16, 2025
  If the Carrier Air Conditioner compressor isn't running, several issues could be the cause. It could be due to an open contactor (check connections), blown fuses in the field power circuit (replace with the correct size fuse after correcting the cause), no control power (check control transformer connections and circuit breaker), or an open thermostat circuit (check thermostat setting). Also, check for an active safety device lockout circuit (reset it), an open low-pressure switch (check for refrigerant undercharge or airflow obstruction), or an open high-pressure switch (check for refrigerant overcharge or airflow obstruction). Other potential causes include an open compressor overtemperature switch (allow for reset or replace if defective), loose electrical connections (tighten them), or...
G
Gregory Dixon IIINov 20, 2025
Why does my Carrier Air Conditioner compressor stop on high-pressure switch?
- D
  diane55Nov 20, 2025
  The Carrier Air Conditioner compressor might stop due to the high-pressure switch being activated. This can happen if the high-pressure switch is faulty (replace the switch), the fan rotation is reversed (confirm and correct if necessary), airflow is restricted (remove obstruction), or air is recirculating (clear airflow area). Other causes include noncondensables in the system or refrigerant overcharge (recover refrigerant and recharge as required), incorrect line voltage (consult power company), or refrigerant system restrictions (check or replace filter drier, expansion valve, etc.). It can also happen if the outdoor fan is off (tighten fan hub setscrews, check power and capacitor, replace bearings, check overload rating and for fan blade obstruction, or replace the motor), or if the fa...
J
Jesse RuizNov 26, 2025
What to do if Carrier 38AUZ compressor cycles on low-pressure switch?
- Q
  qtorresNov 27, 2025
  If the Carrier Air Conditioner compressor cycles on the low-pressure switch, several factors could be responsible. This includes issues like the indoor-air fan running or stopped (tighten all connections), a liquid line solenoid valve failing to open (check and replace if necessary), a plugged filter drier (replace it), or a defective expansion valve power head (replace it). Other potential causes are low refrigerant charge (add charge and check the low-pressure switch setting), restricted airflow (check refrigerant charge), a coil iced up (check refrigerant charge), a dirty coil (clean coil fins), dirty air filters (clean or replace filters), or closed dampers (check damper operation and position). Also, check for loose electrical connections (tighten all connections), a defective fan rel...

Summary

SAFETY CONSIDERATIONS

General Safety Warnings

Covers electrical shock, unit operation, personal injury, and environmental hazards.

INSTALLATION GUIDELINE

Replacement;Retrofit R-22 to Puron

Details requirements for replacing R-22 systems with Puron® refrigerant.

INSTALLATION

Plan for Unit Location

Complete Refrigerant Piping Connections

Steps for connecting refrigerant piping, including line sizing and safety.

Determine Refrigerant Line Sizes

38 AUD Piping Connections

Install Filter Drier(s) and Moisture Indicator(s)

Recommends installing filter driers and moisture indicators near the evaporator coil's TXV.

Install Liquid Line Solenoid Valve

Electrical Connections

Covers units without/with factory disconnects, general wiring, field control, circuit, and transformer wiring.

PRE-START-UP

System Check

Verifying power supply, auxiliary components, wiring, and refrigerant charge.

Turn On Crankcase Heater

Preliminary Charge

Steps for adding initial refrigerant charge to the system before compressor start.

START-UP

Preliminary Checks

Verifying power, heater placement, leak checks, and preliminary charge.

Compressor Rotation

Ensuring correct compressor rotation direction for 3-phase units.

Adjust Refrigerant Charge

Guidelines for adjusting refrigerant charge using charging charts based on pressure and temperature.

OPERATING SEQUENCE

ROUTINE SYSTEM MAINTENANCE

SERVICE

Refrigeration System

Cautions regarding Puron® refrigerant and required equipment design.

Compressor Oil

Information on POE oil, its hygroscopic nature, and handling precautions.

Liquid Line Filter Drier

Comfort Alert Diagnostic Module

Explains the function of the CADM, its inputs, and LED indicators.

Compressor Protection

Covers overtemperature protection, crankcase heater, ASTP, and pressure switches.

NOVATION Coil Cleaning and Maintenance

Instructions for cleaning NOVATION condenser coils using only water.

Repairing NOVATION Condenser Tube Leaks

Totaline Environmentally Sound Coil Cleaner Application Instructions

TROUBLESHOOTING

Compressor Does Not Run

Lists potential causes and solutions for the compressor failing to start.

Compressor Stops on High-Pressure Switch

Identifies reasons for the compressor stopping due to high pressure.

Compressor Cycles on Low-Pressure Switch

Lists causes and solutions for the compressor cycling on the low-pressure switch.

Compressor Running but Cooling Insufficient

Compressor Loses Oil

Carrier 38AUZ Specifications

General

Phase	1
Voltage	208/230 V
Outdoor Unit Dimensions (HxWxD)	Vary depending on model
Indoor Unit Weight	Vary depending on model
Outdoor Unit Weight	Vary depending on model