Weil-McLain Boiler A98 Error — What It Means
A98 is not a universal fault code across all Weil-McLain boiler platforms. The exact meaning depends on your boiler series and the control module installed. Weil-McLain directs technicians to consult the specific model’s installation and service manual because error codes and reset behavior vary by platform. The control reacts to thermostat calls, air pressure switches, and boiler limit signals, so A98 may indicate a lockout related to ignition, gas flow, flame sensing, or a safety limit trip on your particular unit.
Without the exact boiler model number and control board type, it is not possible to verify what A98 means for your system. The manufacturer’s troubleshooting process requires identifying the boiler family, reading the active and past fault history from the control’s diagnostics menu, and then following the model-specific troubleshooting tree. Attempting to replace parts based on the code alone often leads to misdiagnosis because the same code letter-number can mean different things on different Weil-McLain platforms.
Before You Replace Anything
Without the exact model manual, technicians sometimes replace flame sensors or igniters when A98 may actually be a gas valve, pressure switch, or wiring fault. Always pull the control’s fault history and test the inputs named in your model’s diagnostic flowchart before ordering parts.
Common Causes
- Model-specific lockout (~100%) A98 has different meanings on different Weil-McLain control platforms, so the cause cannot be determined without the exact model’s fault table.
Quick Diagnosis
Answer these to narrow it down fast.
Can you find the exact Weil-McLain model number (for example CGi, Ultra, EG, GV) on the rating plate?
No: Take a photo of the rating plate and the control display and call a qualified heating technician who can identify the platform and pull the correct manual.
Does the control display show any other fault codes or blinking LED patterns along with A98?
No: A98 alone still requires the model-specific table, so proceed to the manual or call a pro for diagnostics.
Have you pressed the reset button on the control or the manual reset on the high-limit switch?
No: Try a single reset following your manual's instructions, then observe whether the boiler lights and runs or trips immediately, and report the behavior to your technician.
Step-by-Step Fix
- Turn off power to the boiler at the main switch or circuit breaker and wait thirty seconds.
- Locate the rating plate on the boiler jacket or inside the control panel and write down the complete model number and serial number.
- Download or retrieve the service manual for that exact model from the Weil-McLain website or the paperwork that came with the unit.
- Turn power back on and observe the control display. Record any fault codes, LED blink patterns, or text messages that appear along with A98.
- Look up A98 in the fault code table in your model’s manual. Note the description, the inputs or components named, and the recommended diagnostic tests.
- Follow the manual’s troubleshooting flowchart for A98. This typically includes checking gas pressure at the valve inlet, testing the flame sensor with a multimeter, inspecting the igniter for cracks, and verifying pressure switch operation.
- If the manual directs you to test components and you are not trained in gas appliance service, call a licensed heating technician to perform the voltage, resistance, and pressure checks safely and log the failed part number for warranty or ordering.
Parts Often Needed
| Part | Notes |
|---|---|
| Flame Sensor (model-specific) | Amazon | Order by your boiler’s part number after confirming it is the failed component through resistance or microamp testing. |
| Gas Valve (model-specific) | Amazon | Must match your boiler’s gas type and pressure rating. Confirm with voltage and pressure tests before replacing. |
When to Call a Pro
Call a licensed heating professional immediately if you cannot find your boiler’s model number or service manual, if the fault returns after a single reset, or if you are unfamiliar with gas appliance troubleshooting. Gas boiler diagnostics require multimeters, manometers for gas pressure, and knowledge of safe lockout procedures. Attempting to bypass safeties or swap parts without verifying the fault can create carbon monoxide hazards or damage the control. The manufacturer’s warranty process also requires the exact failed part description and part number, which only proper diagnostics will reveal. A qualified technician will read the control’s fault history, follow the model-specific flowchart, and test each input to pinpoint whether A98 on your unit is ignition, flame-proving, gas supply, or a limit fault.
Rough cost: A pro service call runs about $150-400.