Rheem code C4

What this code means

C4 — low pressure alert. Suction pressure fell below the minimum allowed while the compressor was commanded on.

Which models show it

Rheem RP14, RP16, RP20 heat pumps and Ruud Ultra Series with alert reporting.

What is actually happening

Heat or cool stops; C4 may display on thermostat or outdoor service LED chart.

Is it safe to keep running?

One retry after filter service only.

What a homeowner can safely check

• New filter.
• Open vents.
• Outdoor coil clear.
• Note whether C4 appears only in heat or cool — helps diagnostics.

When to stop

• Suspected leak.
• C4 repeats.

Likely causes ranked

1. 1. Refrigerant leak

   How a tech confirms: Leak detection and repair; weigh charge.

   Typical repair: $280–$1,150 · Air Conditioner Repair cost guide

2. 2. Restricted indoor coil or blower issue

   How a tech confirms: Airflow measurements; coil cleaning.

   Typical repair: $155–$450 · Air Conditioner Repair cost guide

3. 3. Faulty low-pressure switch

   How a tech confirms: Switch versus gauge test.

   Typical repair: $215–$465 · Air Conditioner Repair cost guide

4. 4. Outdoor metering or EEV fault on variable systems

   How a tech confirms: Manufacturer diagnostic port readings.

   Typical repair: $400–$1,050 · Air Conditioner Repair cost guide

Is this the end of this unit?

Major leak on RP series past 12 years — compare coil replacement to new heat pump.

How to clear the code

Power cycle outdoor unit once after five minutes off and filter change.

Why clearing is not fixing it: Low suction returns with leak or restriction still present.

Which trade to call

Call a licensed hvac contractor who works on heat pump equipment. Gas, refrigerant, and combustion faults are not general handyman jobs.

Related codes and symptom guides

Symptom guide: AC Blowing Warm Air

FAQ

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