Ruud Error Code 99: Vent Blockage
Warning: A vent blockage can cause dangerous carbon monoxide buildup. Shut down the furnace immediately and call for professional service.
How to Fix Ruud Code 99
- Step 1: Ensure your CO detectors are working and have fresh batteries. If you hear an alarm, evacuate immediately and call 911.
- Step 2: Visually inspect the outside vent for any obvious obstructions like snow, ice, or debris. If safe to do so, carefully clear away any blockage you can reach from the ground.
- Step 3: Do not attempt to disassemble the furnace or vent pipes yourself. Call a qualified HVAC technician to diagnose and repair the problem.
How to Reset Ruud Code 99
- Turn off the furnace power switch, usually located on or near the unit.
- Turn off the circuit breaker for the furnace. Wait 30 seconds.
- Restore power at the breaker and flip the furnace switch back on.
- Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.
What does 99 mean?
The Ruud 99 error code indicates a blockage in the venting system. This is a serious issue because your furnace vents exhaust gases, including deadly carbon monoxide (CO), to the outside. If the vent is blocked, these gases can back up into your home. This code usually triggers a safety lockout, preventing the furnace from running. The furnace has pressure switches that monitor the venting. If these switches don't see the expected pressure change when the furnace starts, it assumes a blockage and shuts down. Continuing to run a furnace with a blocked vent is extremely dangerous.
Affected Models
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Inducer Motor | 7062-3983 | — |
| Pressure Switch | 42-24170-03 | — |
| Vent Pipe | — | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| 11 | No Ignition | Critical |
| 12 | Flame Failure | Critical |
| 13 | Improper Combustion | Critical |
| 14 | Overheat / Thermal Fuse | Critical |
| 15 | Inlet Temp Sensor Fault | Warning |
| 16 | Outlet Temp Sensor Fault | Warning |
| 21 | Air Supply / Operational Switch | Warning |
| 24 | Flow Sensor Malfunction | Warning |
| 29 | Condensate Neutralizer Issue | Warning |
| 31 | Inlet Water Filter | Warning |