Rheem HVAC Error Code 28: How to Fix It

Q: What does Rheem error code 28 mean?

Rheem error code 28 indicates a suction line temperature sensor fault. The control board is not receiving a valid signal from the thermistor sensor mounted on the suction refrigerant line, which could be due to a failed sensor, damaged wiring, a loose connector, or in some cases a refrigerant or airflow problem causing abnormal temperatures.

Q: Can I keep running my Rheem HVAC with error code 28?

It is not recommended. The suction line sensor protects the compressor from operating under dangerous conditions. Running the system continuously with this fault active may cause the unit to operate in a degraded mode, cycle on and off erratically, or eventually trigger a full safety lockout. Address the fault as soon as possible to avoid more costly repairs.

Q: How much does it cost to fix a Rheem suction line sensor?

A replacement suction line thermistor sensor typically costs $15–$50 for the part. If you do the repair yourself, that is your total cost. If you hire an HVAC technician, expect to pay an additional $75–$150 in labor, bringing the total to roughly $100–$200 depending on your area and the technician's rates.

Q: Will error code 28 go away on its own?

Occasionally, code 28 can be caused by a temporary loose connection that reseats itself, and the code may clear after a power reset. However, if the underlying sensor has failed or wiring is damaged, the code will return. It is best to inspect and test the sensor rather than relying on the fault to resolve on its own.

Q: Where is the suction line on a Rheem HVAC system?

The suction line is the larger of the two copper refrigerant lines that run between your indoor air handler and the outdoor condenser unit. It is usually covered with black foam insulation. The suction line sensor is typically clamped or strapped onto this line near where it connects to the indoor evaporator coil inside the air handler cabinet.

Abstract

Rheem HVAC error code 28 indicates a suction line temperature sensor fault, meaning the control board is receiving an abnormal or missing signal from the sensor that monitors refrigerant temperature on the low-pressure side of the system. This sensor is critical for protecting the compressor and ensuring efficient operation. Left unresolved, this fault can cause the system to shut down on safety lockout or run inefficiently, so addressing it promptly is important.