Rheem R802VA07542117MSA Error Code T081_F: Return Air Sensor Fault

What Does Code T081_F Mean?

Your R802VA07542117MSA is a two-stage, variable-speed furnace, and its Bluetooth Communicating IFC (Integrated Furnace Control) leans on several temperature sensors to run the variable-speed blower intelligently rather than at one fixed speed. The return air sensor is a thermistor that reports the temperature of the air coming back from your home before it passes over the heat exchanger, and the control uses that reading as one input for airflow and temperature-rise calculations. Code T081_F is logged when the resistance the IFC sees from that thermistor falls outside the valid range, which normally means the sensor has failed open, has come unplugged, or has a corroded connector.

Because this is a monitoring input and not a combustion-safety device, the furnace does not lock out over it. Rheem rates T081_F as a low-severity fault, and in practice the burner still lights and the blower still delivers heat. What you lose is optimization: without a trustworthy return-air reading, the control falls back to default airflow behavior instead of tuning itself to actual conditions, so efficiency and comfort can drift slightly from their best.

T081_F belongs to a family of temperature and pressure sensor faults this board can report. It is the return-air member of the air-temperature group, alongside T082_F (supply air) and T084_F (outdoor air). A separate group of codes, T085_F, T086_F and T088_F, covers the cooling system's electronic expansion valve sensors, and T087_F watches the control board's own temperature. All of these are low-severity monitoring faults and should not be confused with the hard-lockout codes on this furnace, which shut heating down for safety.

Because the return air sensor and the supply air sensor are read together for temperature-rise math, it is not unusual to see T081_F and T082_F appear around the same time if a shared wiring harness or connector is disturbed.

What You'll Notice

• The alphanumeric display shows "T081_F", or the LED blinks the code one digit at a time with a roughly three-second pause between digits
• The furnace continues to light and produce heat, so nothing obvious seems wrong at the registers
• Heating may feel slightly less efficient or the airflow less finely matched to conditions than before
• The fault reappears in the Bluetooth contractor app history even after a power cycle
• No lockout occurs and the thermostat is still answered normally

Common Causes

How This Is Diagnosed

A technician confirms T081_F by locating the return air thermistor and its connector at the control board, then measuring the sensor's resistance and comparing it against the expected value for the current ambient temperature. A reading that is open or wildly out of range points to a failed thermistor, while a good reading at the sensor but a bad reading at the board points to a broken wire or a loose or corroded connector.

The wiring harness and plug are inspected for chafing, moisture and green corrosion, and the connector is reseated. If the resistance is correct and stable at the board but the code persists, the technician looks at the control's sensor input itself. This is informational only; sensor and board work on this furnace is not homeowner-safe.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• The code stays active and you want the furnace returned to full efficiency rather than running on default airflow
• You also see the supply air code T082_F, suggesting a shared harness or connector problem
• Heating comfort or run times have noticeably changed since the code appeared
• The fault clears and returns repeatedly, hinting at an intermittent connection rather than a dead sensor

✓ Verified against manufacturer service manual — March 2026