Weil-McLain 019 Error Code — What It Means
Error code 019 (sometimes misread as A19) means the boiler attempted to ignite but failed to detect a flame within the prescribed ignition time window, typically 15 to 30 seconds. The control board has entered a lockout state to prevent unburned gas from accumulating in the combustion chamber. This fault indicates either the burner did not light at all, or the flame sensor did not detect the flame even though combustion may have occurred. The control board will not attempt another ignition cycle until the system is manually reset.
On Weil-McLain models with Intelli-Fire, Ultra Logic, or AquaBalance control boards, this code appears as a three-digit numeric display (019) or sometimes with a prefix like E019, depending on the board generation. The boiler is designed to lock out after a set number of failed ignition trials to protect against gas buildup and make sure safe operation.
Before You Replace Anything
Homeowners often replace the gas valve or ignitor first. Before buying parts, test for spark at the electrode and clean the flame sensor rod with fine steel wool or emery cloth. A dirty sensor is the usual culprit.
Common Causes
- Dirty or corroded flame sensor rod (~40%) Soot, carbon deposits, or oxidation coat the flame rod and prevent it from detecting the micro-amp signal from the flame, causing lockout even when the burner lights.
- Gas supply problems (~25%) The gas valve is not fully open, gas pressure is below specification, or the meter or upstream valve is shut off, preventing fuel from reaching the burner.
- Faulty ignitor or spark electrode (~15%) The ignitor is cracked, worn, or failed, producing no spark or a weak spark that cannot ignite the gas, or the spark gap is misaligned.
- Clogged burner ports (~10%) Debris, soot, spider nests, or dust block the burner openings and prevent proper air-gas mixing or flame propagation, stopping ignition.
- Air pressure switch failure (~5%) The air pressure or draft switch does not close to prove combustion airflow, so the control board will not energize the ignitor or gas valve.
- Control board relay or output failure (~5%) The board fails to send voltage to the ignitor or gas valve due to a stuck relay or failed output circuit, preventing the ignition sequence.
Quick Diagnosis
Answer these to narrow it down fast.
Do you hear a rapid clicking sound (spark) when the boiler tries to light?
No: No spark means a failed ignitor, broken wire, or control board output problem. Check voltage to the ignitor and inspect the electrode for cracks.
Is the gas supply valve handle in line with the pipe (fully open)?
No: Turn the valve handle in line with the pipe to open it fully, then reset the boiler and retry. If it still fails, check upstream gas supply.
Does the flame sensor rod look clean and shiny, or is it covered in black soot or white oxidation?
No: Clean the rod with fine steel wool or emery cloth until it is shiny metal, then reinstall and reset the boiler. This often solves the problem.
Step-by-Step Fix
- Turn off power and gas to the boiler at the service switch and the gas supply valve. Wait 5 minutes for any residual gas to dissipate.
- Verify gas supply by confirming the gas valve handle is in line with the pipe (open position) and the gas meter dial is moving or digital display shows flow to other appliances.
- Restore power and listen for the ignition sequence. Turn power back on and set the thermostat to call for heat. Listen for a rapid clicking sound (spark) and observe the burner area through the sight glass if available.
- Inspect the spark and flame sensor by removing the front cover or access panel. Locate the ignitor electrode and flame sensor rod (usually a single thin metal rod near the burner). Check for a strong blue spark jumping the gap and verify the flame rod is not bent or coated.
- Clean the flame sensor rod by unscrewing or unclipping the rod from its bracket. Use fine steel wool, emery cloth, or a non-metallic abrasive pad to polish the rod until it is shiny and free of soot, carbon, or white oxidation. Reinstall the rod in the same position.
- Check and clean the burner by inspecting the burner ports for blockages. Use a vacuum and soft brush to remove dust, debris, or spider webs. Do not use compressed air, which can push debris deeper into the gas valve.
- Reset the boiler and test by cycling power off for 30 seconds, then back on. Set the thermostat to call for heat and observe whether the burner lights and the flame is stable. If the code returns, proceed to test gas pressure and ignitor voltage or call a technician.
Parts Often Needed
| Part | Notes |
|---|---|
| Flame sensor rod (flame detection electrode) | Amazon | Order the rod specific to your Weil-McLain model number. Most rods are universal-fit but verify length and thread size. |
| Ignitor electrode assembly | Amazon | Includes the spark electrode and ceramic insulator. Match the part number on your existing ignitor or consult the boiler model plate. |
When to Call a Pro
Call a qualified HVAC or boiler technician if you do not hear a spark, if you smell raw gas during the ignition attempt, or if cleaning the flame sensor and checking the gas supply does not resolve the lockout. Gas appliances require proper combustion analysis, pressure testing, and electrical diagnostics that go beyond homeowner tools. A technician will use a multimeter to test ignitor voltage (typically 120VAC), measure gas inlet pressure with a manometer (consult your model’s specification table for required pressure), check the flame sensor micro-amp signal (usually 0.5 to 10 microamps), and inspect the air pressure switch and wiring. If the control board has failed or the gas valve is defective, replacement requires gas line work and must be done by a licensed professional to meet local codes and maintain warranty coverage.
Rough cost: A pro service call runs about $150-300.