Weil-McLain A13 Error Code — What It Means
The A13 code is not a universal fault code across all Weil-McLain boilers. Weil-McLain uses different control platforms (including AquaBalance and others), and each platform has its own fault table with unique error definitions. The exact meaning of A13 depends on your specific boiler model and control board. The manufacturer expects technicians to identify the exact model from the nameplate and serial label, then consult that model’s service manual for the fault table entry before diagnosing.
Without the specific manual, it is impossible to know whether A13 relates to a sensor, flow switch, ignition component, or another system on your unit. Attempting to diagnose or reset the code without the correct manual risks misdiagnosis and wasted parts replacement. Locate your boiler model number and retrieve the matching service manual from Weil-McLain or your installer to find the precise fault definition and required checks.
Before You Replace Anything
Technicians sometimes replace control boards or sensors without first consulting the model-specific fault table, wasting hundreds of dollars. Always retrieve the exact fault definition from your boiler’s manual before ordering parts.
Common Causes
- Model-specific sensor fault (~30%) The code may indicate a temperature, pressure, or flow sensor issue unique to your control platform and must be verified in the manual.
- Wiring or connector problem (~25%) Loose, corroded, or damaged wiring to a sensor or safety device can trigger fault codes that vary by model.
- Flow or circulation interlock (~20%) Some control platforms use this range of codes for low flow, blocked pump, or air in the system.
- Combustion or ignition fault (~15%) Certain models assign A-series codes to flame-proving or gas-valve safety lockouts.
- Control board fault or software (~10%) The control may flag an internal error or require a firmware check, depending on the platform.
Quick Diagnosis
Answer these to narrow it down fast.
Do you have the service manual for your exact boiler model?
No: Write down your complete model and serial number, then contact Weil-McLain technical support or your installer to obtain the correct manual before proceeding.
Is the boiler display showing A13 as a current active fault (not just in stored history)?
No: The fault was stored from an earlier event; check the manual to see if it requires service or was a transient issue that cleared.
Does your boiler use an AquaBalance or similar digital control with a multi-line display?
No: Your control may be a different platform; verify the control model from the label inside the jacket and request that control's manual.
Step-by-Step Fix
- Record the complete boiler model number and serial number from the nameplate on the boiler jacket or inside the door.
- Obtain the service manual for that exact model from Weil-McLain technical support, your installer, or the manufacturer’s professional portal.
- Locate the fault-code table in the manual and find the A13 entry to read the exact fault description and listed causes.
- Inspect the component or sensor named by the manual’s A13 definition, checking wiring, connectors, and mechanical condition.
- Test the suspected component electrically (resistance, continuity, or voltage as specified in the manual) and mechanically (operation, flow, or pressure).
- Replace only the failed part identified by your tests, using the part number from the manual or parts diagram.
- Clear the fault from the control menu or by cycling power, then verify normal ignition, flame stability, temperature rise, and circulation before leaving the boiler in service.
Parts Often Needed
| Part | Notes |
|---|---|
| Temperature or pressure sensor (model-specific) | Amazon | Order by exact part number from the manual; sensors vary by control platform and boiler series. |
| Flow switch or proving switch | Amazon | Used on many condensing models; confirm the manual identifies this as the A13 cause before ordering. |
| Control board or module | Amazon | Only replace after testing sensors and wiring; control boards are expensive and rarely the root cause of sensor faults. |
When to Call a Pro
Call a licensed boiler technician immediately if you do not have the service manual for your model, if the boiler is under warranty (Weil-McLain requires documented diagnosis and part numbers for claims), or if the fault involves gas supply, combustion air, venting, or high-voltage wiring. Professional diagnosis is necessary because A13 has no universal meaning and the correct repair depends entirely on the control platform and model-specific fault table. Attempting repairs without the manual risks wasting money on the wrong part or creating a safety hazard. A qualified technician will retrieve the fault history, test the exact component named in your manual, and document the failure for warranty purposes.
Rough cost: A pro service call runs about $150-400.