Weil-McLain Boiler A152 Error — What It Means
A152 does not appear in verified Weil-McLain service manuals or control documentation. Weil-McLain fault codes are specific to the boiler model and control platform installed. The code you see may be a lockout or fault history entry, but without your exact model number and control type, the manufacturer-verified meaning cannot be confirmed.
To find what A152 actually means on your boiler, retrieve the full fault name (not just the number) from the control’s diagnostic menu and compare it to your model-specific installation and service manual. The fault could relate to a temperature sensor, low-water cutoff, ignition fault, flame sensor, gas valve issue, or circulator problem, but guessing without the manual risks replacing the wrong part.
Before You Replace Anything
Homeowners often replace thermistors, flame sensors, or igniters based on unfamiliar codes without first checking the control fault history and basic system conditions. Pull the stored fault history from the control menu and verify boiler pressure, power, gas supply, and thermostat call before buying any part.
Common Causes
- Unknown or model-specific code (~40%) A152 does not match documented Weil-McLain fault codes, so the exact meaning depends on your boiler model and control platform.
- Low boiler water pressure or low-water cutoff trip (~25%) Pressure below 12 psi can trigger a safety lockout on many Weil-McLain controls.
- Temperature sensor or thermistor fault (~15%) A failed or mis-wired thermistor can produce a control lockout or history entry.
- Ignition or flame-sensing fault (~10%) Igniters, flame sensors, and gas valve circuits can log faults that appear as numeric codes.
- Circulator fault or flow issue (~10%) Air-locked system, failed circulator, or blocked flow can prevent heat delivery and trigger a fault.
Quick Diagnosis
Answer these to narrow it down fast.
Is the boiler water pressure below 12 psi on the gauge?
No: Pressure is likely okay. Move to the control fault history check.
Can you access the control diagnostic menu and read a stored fault name (not just A152)?
No: Call a qualified heating technician to retrieve the fault history and interpret it correctly for your model.
Does the boiler attempt to fire (you hear the igniter clicking or the circulator running)?
No: The control may be in lockout. Check that the thermostat is calling for heat, the boiler has power, and gas is on before resetting.
Step-by-Step Fix
- Turn off power to the boiler at the service switch or breaker.
- Check the boiler water pressure on the gauge. If below 12 psi, open the fill valve slowly until pressure reaches around 15 psi, then close it.
- Restore power and access the control diagnostic or history menu (consult your model’s manual for the button sequence).
- Record the full fault name displayed in the history, not just the numeric code A152.
- Look up the fault in your boiler’s installation and service manual under the Troubleshooting or Fault Codes section.
- Test the component identified by the fault (thermistor, low-water cutoff, flame sensor, igniter, gas valve, or circulator) using the manual’s procedures and specifications.
- Replace the confirmed failed component and reset the control. Monitor the boiler through a full heating cycle to make sure the fault does not reappear.
Parts Often Needed
| Part | Notes |
|---|---|
| Thermistor / temperature sensor | Amazon | Order by your exact Weil-McLain model number and control type. |
| Low-water cutoff sensor | Amazon | Verify part number from your model’s service manual or parts list. |
| Igniter or ignition module | Amazon | Match to your boiler’s gas valve and control platform. |
| Flame sensor | Amazon | Confirm fitment and wiring from your model’s wiring diagram. |
When to Call a Pro
Call a qualified heating technician if you cannot retrieve the fault history from the control menu, if you are unfamiliar with gas appliance service, or if you do not have the model-specific service manual and wiring diagrams. Weil-McLain boilers are gas-fired safety appliances that require specialized tools and training to diagnose sensor circuits, test gas valves, measure flame current, and replace control modules. Incorrect diagnosis or improper part replacement can create carbon-monoxide hazards, flood the combustion chamber with unburned gas, or damage the control. A technician will pull the full fault history, identify the exact component from the manufacturer’s troubleshooting tables, and test it before ordering parts.
Rough cost: A pro service call runs about $200-450.