Weil-McLain Boiler A87 Error Code — What It Means
A87 does not appear as a documented fault code in Weil-McLain boiler service literature. Weil-McLain uses different control platforms across their models, and each control system has its own fault code definitions. What appears as A87 on your display may be a misread code, a fault history entry, or a code specific to a third-party control board installed during a retrofit. The exact meaning depends entirely on your boiler model number and the type of control display you have.
Before attempting any repair, locate the model number and serial number on the boiler nameplate. Write down exactly what the control display shows, including any other letters, numbers, or flashing patterns. Access the fault history or lockout menu if your control supports it (button sequences vary by model). Only after you have the model and control type can you look up the real fault definition in the manufacturer’s installation and service manual for that specific unit.
Before You Replace Anything
Do not order or replace any parts based on an unverified code number. Confirm the exact fault definition in your model’s manual before diagnosing, or you may replace a working sensor or board unnecessarily.
Common Causes
- Misread or misinterpreted display (~35%) The code may actually be a different letter or number that looks similar, or a lockout counter rather than a fault code.
- Model-specific code not in general documentation (~30%) Some Weil-McLain models and aftermarket control boards use proprietary codes that require the exact model manual to decode.
- Fault history entry rather than active code (~20%) The display may be showing a past error stored in memory rather than a current lockout condition.
- Third-party control retrofit (~10%) If the original control was replaced with an aftermarket board, the fault codes will follow that manufacturer’s system instead of Weil-McLain’s.
- Display or control board fault (~5%) A failing display or corrupted firmware can show nonsense codes that do not correspond to any real fault condition.
Quick Diagnosis
Answer these to narrow it down fast.
Does the boiler model number start with EG, CG, GV, or Ultra?
No: Write down the full model number and control board part number, then call Weil-McLain technical support or a licensed boiler technician to identify the control platform.
Does the display show any other codes or messages when you scroll through the menu?
No: Power-cycle the boiler and watch the display during startup to see if the code reappears or changes to a recognized fault.
Did the boiler have any recent service or control board replacement?
No: Gather the model number, control board part number, and a photo of the display, then call a licensed boiler service company for diagnosis.
Step-by-Step Fix
- Turn off power to the boiler at the service switch or breaker and wait 30 seconds.
- Locate the boiler nameplate (usually on the jacket or inside the front panel) and write down the complete model number, serial number, and date of manufacture.
- Identify the control board by opening the control compartment and reading the label on the board itself, note the manufacturer and part number if visible.
- Restore power and observe the display as the boiler powers up, write down every code, message, or flashing pattern that appears.
- Access the fault history menu if your control supports it (button sequences vary, consult the manual or try pressing and holding the reset button for five seconds).
- Download the service manual for your exact model from the Weil-McLain website or contact their technical support line with the model and control information.
- Do not replace any parts until you have confirmed the fault definition and performed the diagnostic tests specified in the model manual or with guidance from a licensed technician.
Parts Often Needed
| Part | Notes |
|---|---|
| Weil-McLain control board (model-specific) | Amazon | Only order after confirming the part number from the boiler nameplate and verifying the board is faulty, not a sensor or wiring issue. |
| Flame sensor or probe | Amazon | Common across many models, but the exact part number and connector type vary, confirm fit before ordering. |
When to Call a Pro
Call a licensed boiler technician immediately if you cannot locate the model number, if the manual for your model does not list the code you see, or if the boiler is locked out and will not fire. Gas-fired boiler diagnostics require combustion analysis, pressure testing, and electrical measurements that are not safe or practical for a homeowner. A pro will identify the control platform, pull the real fault history, test safeties and sensors with a multimeter, and verify proper combustion and venting. If the code turns out to be a control board or gas valve issue, the technician can source the correct part and complete any required startup and warranty registration. Do not bypass safeties or attempt to force the boiler to run without understanding the fault.
Rough cost: A pro service call runs about $150-400.