Weil-McLain A82 Error Code — What It Means
Weil-McLain does not publish a universal definition for an A82 error code in their standard documentation. The code may be model-specific, or it may have been misread from the control display. Weil-McLain directs owners to consult the exact boiler model manual and to have a local heating professional interpret fault codes using the contractor diagnostics menu, not just the front-panel display.
Most Weil-McLain boiler lockouts stem from ignition or flame-proving problems. The control monitors gas valve status, ignitor function, and flame presence. When any of those signals fall out of range or when the control cannot verify stable combustion, it locks out and displays a fault. Common real-world triggers include no gas supply, a dirty or failed flame sensor, a fouled ignitor, blocked venting or combustion air, and condensate drain blockages on condensing models.
Before You Replace Anything
Homeowners often replace the ignitor or control board before checking whether gas is flowing or the flame sensor is dirty. Verify gas supply at the manual shutoff and incoming pressure, then clean the flame sensor, before ordering expensive parts.
Common Causes
- Dirty or failed flame sensor (~30%) Carbon or soot on the flame-sensing rod prevents the control from proving flame even when the burner lights.
- No gas supply or closed manual shutoff (~25%) The boiler cannot ignite if the gas valve upstream is closed, the meter is off, or incoming pressure is too low.
- Failed or fouled ignitor (~20%) A cracked, corroded, or out-of-spec ignitor will not produce a strong enough spark or glow to light the gas.
- Blocked venting or combustion air (~15%) Ice, condensate freeze-up, bird nests, or disconnected piping starve the burner of air or block exhaust, triggering a safety lockout.
- Condensate trap or drain blockage (~10%) On condensing boilers a plugged trap or frozen drain line raises pressure in the heat exchanger and trips a safety switch.
Quick Diagnosis
Answer these to narrow it down fast.
Does the display show a different code or number when you power-cycle the boiler?
No: The fault is persistent. Proceed to verify gas supply and check the flame sensor and ignitor.
Can you hear the gas valve click and the ignitor spark or glow when the boiler tries to fire?
No: No ignition attempt means the control is not commanding the gas valve. Check incoming power, control fuses, and safety-circuit interlocks.
Is there visible ice, water, or debris at the outdoor vent termination?
No: The vent system is clear. Focus on gas supply, flame sensor, and ignitor condition inside the boiler.
Step-by-Step Fix
- Turn off power at the boiler switch and the circuit breaker, then turn off the manual gas shutoff and wait five minutes for any residual gas to clear.
- Locate the exact model and serial number on the boiler nameplate and download or retrieve the installation and service manual for that model from Weil-McLain’s website or your installer’s records.
- Check the contractor diagnostics menu on the control by following the button-press sequence in your manual. Write down all stored fault codes and the fault history rather than relying only on the front-panel display.
- Verify gas supply by confirming the manual shutoff is open, checking that other gas appliances in the home are working, and using a manometer to measure inlet pressure at the boiler’s gas-valve test port against the spec in your model manual.
- Inspect and clean the flame sensor by removing the sensor rod from the burner assembly, wiping it gently with fine-grit emery cloth or a Scotch-Brite pad until the metal is bright, and reinstalling it with the tip positioned correctly in the flame path per the manual.
- Check the ignitor for cracks, corrosion, or carbon buildup. If it is a hot-surface ignitor, measure its resistance with a multimeter and compare to the spec in the manual. If it is a spark ignitor, verify the ceramic is intact and the gap to ground is correct.
- Inspect venting and combustion air by walking the entire vent run from the boiler to the outdoor termination, looking for disconnected joints, sagging pipe, ice dams, and obstructions, and clearing any blockage you find.
- Check the condensate system on condensing models by removing and flushing the trap, verifying the drain line is not frozen or plugged, and confirming the trap is refilled to the correct water level before reassembly.
- Restore power and gas then initiate a call for heat and observe the ignition sequence. The control should command the gas valve, the ignitor should energize, the burner should light within a few seconds, and the flame sensor should prove flame and keep the valve open.
- Reset the lockout only once after correcting the underlying fault. If the boiler locks out again on the same code, stop and call a qualified heating technician for advanced diagnostics of the control, gas valve, and safety circuits.
Parts Often Needed
| Part | Notes |
|---|---|
| Flame sensor rod | Amazon | Model-specific; verify the part number in your boiler’s service manual or on the existing sensor. |
| Hot-surface ignitor or spark electrode | Amazon | Match the exact ignitor type and voltage rating to your boiler model. |
When to Call a Pro
Call a licensed heating professional immediately if you smell gas, if the boiler repeatedly locks out after one reset, if you are not comfortable working with gas piping or high-voltage ignition components, or if the fault history shows multiple different codes that suggest a control or wiring problem. Gas appliance diagnostics require proper test equipment, including a manometer for gas pressure, a multimeter for electrical checks, and a combustion analyzer to verify safe operation. A technician will also access the contractor-level diagnostics on the control, interpret model-specific fault definitions that are not published in the homeowner manual, and confirm that all safety interlocks and limit switches are functioning correctly before returning the boiler to service.
Rough cost: A pro service call runs about $150-350.