Ruud Error Code 13: Improper Combustion
How to Fix Ruud Code 13
- Step 1: Immediately shut off the furnace at the breaker.
- Step 2: Ensure you have working carbon monoxide detectors in your home, especially near sleeping areas. If you don't have them, install them immediately.
- Step 3: Open windows and doors to ventilate your home.
- Step 4: Call a qualified HVAC technician to inspect and repair the furnace. Do not attempt to restart the furnace until it has been inspected.
How to Reset Ruud Code 13
- 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.
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 Ruud Error Code 13 Mean?
Ruud error code 13, 'Improper Combustion,' means the furnace isn't burning fuel correctly. This can happen for several reasons, but the most important thing is that it could lead to a dangerous buildup of carbon monoxide (CO) in your home. CO is a colorless, odorless gas that can be deadly. The furnace's control board constantly monitors the flame and exhaust to ensure proper combustion. When it detects a problem, it shuts down the furnace and displays this error code to prevent further risk. Specifically, the system is likely detecting either a weak flame, a flame that's not properly established, or excessive carbon monoxide in the exhaust gases. This could be due to a gas supply issue, a problem with the burner, or a venting problem that's preventing the exhaust gases from escaping your home. Because of the safety risks involved with improper combustion, it's important to have a qualified technician diagnose and repair the problem as soon as possible.
Common Causes
- Blocked or restricted flue/venting system
- Dirty or faulty flame sensor
- Low gas supply pressure
- Malfunctioning gas valve
- Cracked heat exchanger
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Furnace is locked out on code 13 | Measure gas supply pressure at the gas valve with a manometer | 7-10 inches of water column (WC) for natural gas, 11-13 inches WC for propane |
| Gas pressure is within range | Inspect the flame sensor for dirt or damage. Measure the flame sensor microamp signal when the burners are lit. | Flame sensor should be clean and free of cracks. Microamp signal should be between 2-10 uA DC. |
| Flame sensor signal is weak or erratic | Check the flame sensor rod for proper placement in the flame. Check the wire connections to the flame sensor and control board. | Flame sensor rod should be fully engulfed in the flame. Wire connections should be clean and tight. |
| Venting appears obstructed | Visually inspect the vent pipe for any obvious obstructions or damage. Use a manometer to measure draft pressure. | Vent pipe should be clear of obstructions. Draft pressure should be within manufacturer's specifications (typically negative pressure). |
Applicable Ruud Models
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Flame Sensor | 41-401 | — | Find Part |
| Gas Valve | 7061173 | — | Find Part |
| Pressure Switch | — | — | — |
Related Codes on Same Models
Other codes that affect the same Ruud model families as 13.
| Code | Description | Severity |
|---|---|---|
| 11 | No Ignition | Critical |
| 12 | Flame Failure | 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 |
| 33 | Fan Motor Fault | Warning |