Rheem Error Code A031: Inlet Thermistor Open/Short

Severity
Warning
Type
digital display
Where to look
front panel
Estimated repair cost: $100 — $250 (parts + labor)
Warning: Your Rheem HVAC system has detected an issue with the inlet thermistor and has shut down to prevent damage.

How to Fix Rheem Code A031

  1. Step 1: Turn off the power to your HVAC system at the circuit breaker.
  2. Step 2: Inspect the wiring leading to the inlet thermistor for any visible damage or disconnection.
  3. Step 3: If you're comfortable, check the thermistor's resistance using a multimeter. If it's not within the specified range (usually between 10,000 to 100,000 ohms), it may be faulty. If not, call a professional HVAC technician.

How to Reset Rheem Code A031

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

What does A031 mean?

The Rheem A031 error code indicates that there's an open or short circuit in the inlet thermistor, which is responsible for measuring the temperature of the incoming air. This could be due to a faulty thermistor, a broken wire, or a problem with the circuit board. The system has entered a safety lockout mode to protect itself from further damage. You'll need to address this issue to restore normal operation.

Affected Models

Replacement Parts

PartOEM NumberEst. Cost
Inlet Thermistor 40-00103 —

Related Codes on Same Models

CodeDescriptionSeverity
A001 Ignition Failure Warning
A003 Abnormal Ignition Warning
A004 False Flame Detection Warning
A008 Exhaust Temperature High Warning
A011 No Flame Detected Warning
A021 Over-Temperature Warning
A041 Outlet Thermistor Open/Short Warning
A043 Water Level Error Warning
A051 Fan Motor Abnormality Warning
A052 Fan Motor Speed Error Warning