Weil-McLain Boiler A69 Error — What It Means
The A69 code on a Weil-McLain boiler indicates an ignition or flame-proving fault. The control tried to light the burner but either did not detect a valid flame signal or the flame was lost during the proving cycle. In field terms, this is a failed ignition lockout rather than a single-component failure.
The boiler may go through its prepurge sequence and spark or glow, but if the control does not sense stable flame within the proving window, it locks out and displays A69. The exact label and behavior can vary by model family and control board, so always verify against your specific boiler’s service manual and error-code chart before troubleshooting.
Before You Replace Anything
Many people replace the gas valve or control board first. Instead, pull and clean the flame sensor rod with fine emery cloth and check that the gas service valve is fully open. These two checks solve most A69 faults without buying parts.
Common Causes
- Dirty or failed flame sensor (~40%) Carbon and soot contamination on the flame rod prevent the control from detecting flame rectification current, even when the burner lights.
- No gas flow (~25%) A closed manual gas valve, interrupted supply, or insufficient inlet pressure stops the burner from lighting at all.
- Failed ignitor or electrode (~15%) A cracked hot-surface igniter or fouled spark electrode will not produce enough heat or spark to light the gas.
- Loose wiring or poor grounding (~10%) Disconnected harness plugs or a missing chassis ground path interfere with flame sensing and ignition control circuits.
- Failed gas valve (~7%) The valve coil may not open, or internal seats may be stuck, blocking gas even when commanded to open.
- Failed control board (~3%) If all ignition and sensing components test good, the ignition control module itself may have a fault in the flame-sense circuit.
Quick Diagnosis
Answer these to narrow it down fast.
Do you see or hear the ignitor glow or spark when the boiler calls for heat?
No: The ignitor may have failed or the control is not sending voltage. Check wiring to the ignitor and test the ignitor for continuity.
Does the burner light briefly then go out and lock out on A69?
No: The burner is not lighting at all. Confirm gas is flowing to the valve and check inlet pressure per your manual.
Have you reset the boiler more than twice without fixing the underlying cause?
No: Proceed with the diagnostic sequence below, correcting any faults before attempting a single reset.
Step-by-Step Fix
- Verify your exact boiler model and control by reading the data plate and opening the correct Weil-McLain service manual or error-code chart for that family.
- Confirm gas supply by checking that the manual service valve is fully open, the meter valve is on, and other gas appliances in the building are working.
- Observe an ignition trial by calling for heat and watching whether the ignitor glows or sparks and whether the burner lights, even briefly.
- Inspect and clean the flame sensor by shutting off power and gas, removing the flame rod from the burner assembly, and polishing the sensing tip with fine emery cloth or steel wool until shiny.
- Check the ignitor for cracks, carbon tracking, or incorrect gap if it is a spark type, or for a broken element if it is hot-surface. Replace if damaged.
- Verify wiring and grounding by inspecting all harness connectors to the control board, ignitor, gas valve, and flame sensor. Tighten the chassis ground screw and check continuity to the boiler frame.
- Reset the boiler once after correcting the fault, then monitor a full ignition cycle to confirm stable flame and normal operation. If A69 returns, stop and proceed to component-level testing per the manual.
Parts Often Needed
| Part | Notes |
|---|---|
| Flame sensor rod (flame rectification probe) | Amazon | Match the thread and length to your Weil-McLain model and control family. |
| Hot-surface ignitor or spark electrode | Amazon | Specify your boiler model number when ordering to make sure correct voltage and mounting. |
| Gas valve | Amazon | Only replace after verifying the valve is not opening and inlet pressure is correct per the manual. |
| Ignition control board | Amazon | Last-resort part. Confirm all field wiring and components test good before ordering. |
When to Call a Pro
Call a licensed HVAC technician immediately if you are not comfortable working around natural gas or propane. Gas work requires proper tools, pressure gauges, and combustion analysis to verify safe operation. Also call a pro if you have cleaned the flame sensor and confirmed gas supply but the fault returns, if you smell gas at any time, or if the boiler has gone through more than two resets without resolving the issue. Repeated ignition attempts without fixing the root cause can damage the control and create unsafe combustion conditions. A qualified technician will perform inlet and manifold pressure checks, test ignition voltage and flame rectification current, and verify proper venting and combustion air before clearing the fault.
Rough cost: A pro service call runs about $150–350 depending on parts and labor.