Rheem Error Code A031: Inlet Thermistor Open/Short
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
- Step 1: Turn off the power to your HVAC system at the circuit breaker.
- Step 2: Inspect the wiring leading to the inlet thermistor for any visible damage or disconnection.
- 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
- Turn off the unit using the power button on the front panel.
- Turn off the gas supply valve.
- Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
- Restore power at the breaker, then open the gas valve.
- Turn the unit back on. If the error returns, the underlying issue needs repair.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Rheem Error Code 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.
Common Causes
- Faulty inlet thermistor
- Broken wire leading to the thermistor
- Issue with the circuit board
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| System displays A031 error | Measure resistance of inlet thermistor | Between 10,000 and 100,000 ohms |
| Resistance is out of range | Inspect thermistor and wiring for damage | No visible damage |
Applicable Rheem Models
- NCB(gas)
- NPE(electric)
- R801T(gas)
- R92E(electric)
- R92V(gas)
- RGE(gas)
- RH2T(electric)
- RNC(dual_fuel)
- RNE(electric)
- RNG(gas)
- RP16(electric)
- RPB(gas)
- RTGH(gas)
- Rheem Classic(gas)
- Rheem Classic 80 Plus(gas)
- Rheem Classic 80% Gas Furnace(gas)
- Rheem Classic 90 Plus(gas)
- Rheem Classic Plus Series(gas)
- Rheem Classic Series(dual_fuel)
- Rheem Prestige(gas)
- Rheem Prestige 95% Gas Furnace(gas)
- Rheem Prestige Series(gas)
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Inlet Thermistor | 40-00103 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Rheem model families as A031.
| Code | Description | Severity |
|---|---|---|
| A001 | Ignition Failure | 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 |
| A053 | Fan Motor Open Circuit | Warning |
| A054 | Fan Motor Overcurrent | Warning |
| A055 | Fan Motor Locked | Warning |
| A095 | DIP Switch Error | Warning |