Bryant 315AAV Error Code 31: High-Heat Pressure Switch Open or Relay Did Not Close
What Does Code 31 Mean?
Status code 31 on the Bryant 315AAV is a high-heat pressure switch open or relay-did-not-close fault. This furnace proves adequate draft separately for its low-heat and high-heat operation, and code 31 sets when the control cannot confirm the high-heat pressure switch has closed as it should when high-heat is commanded.
Bryant lists three things to check: a high-heat pressure switch stuck open, a defective control relay that failed to close the circuit, and a gas valve that is reversed. The control also directs you to see status code 32, the low-heat pressure switch open code, because the two staged pressure switches are diagnosed together — code 31 is specifically about the high-heat proof, while code 32 concerns the low-heat proof, and code 43 flags a disagreement where the low-heat switch is open while the high-heat switch is closed.
Every listed cause — pressure switch, control relay, or gas valve orientation — requires meters, draft knowledge, or gas-side work, so this is a technician repair, not a homeowner task.
What You'll Notice
- The furnace runs on low heat but will not step up to, or sustain, high-heat operation
- The status LED flashes three short then one long flash
- Heating output seems weak on the coldest days because high-heat cannot be verified
- The problem may follow a gas valve or pressure-switch repair if parts were reversed or mis-set
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| High-heat pressure switch stuck open | Most common | ✗ Call a pro → |
| Defective control relay | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician evaluates the high-heat draft proof in order: confirm the inducer is producing adequate high-heat draft, test whether the high-heat pressure switch is stuck open, and check the control relay that must close for high-heat. They also verify the gas valve is not reversed, since Bryant lists that as a cause, and cross-reference status code 32 because the low-heat and high-heat pressure switches are assessed as a pair.
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 furnace will not run on or maintain high heat
- The high-heat pressure switch is suspected stuck open or the control relay is not closing
- The code appeared after a gas valve or pressure-switch replacement
- Any pressure-switch, relay, or gas-valve diagnosis, which is not a homeowner repair
Frequently Asked Questions
Why does my Bryant 315AAV heat on low but not high?
Code 31 means the control cannot verify the high-heat pressure switch closed, so it will not run high heat. Causes include a stuck-open high-heat switch, a defective relay, or a reversed gas valve.
How does code 31 relate to code 32?
Code 31 is about the high-heat pressure-switch proof, and code 32 is about the low-heat pressure-switch proof. The manual cross-references them because the staged pressure switches are diagnosed together.
Can I reset it and keep running the furnace?
Cycling power may clear it temporarily, but the stuck switch, bad relay, or reversed valve remains. It should be diagnosed by a technician before relying on the furnace.
Sources
✓ Verified against manufacturer service manual — March 2026