Weil-McLain error codes — full list with meanings | TroubleAtlas

🌐 ▾

🇬🇧 English 🇮🇹 Italiano 🇩🇪 Deutsch 🇫🇷 Français 🇪🇸 Español

HVAC Error Codes · Manufacturer index

Weil-McLain error codes

The complete list of Weil-McLain fault codes shown on the display, each with what it means and the page that explains how it is diagnosed and fixed.

48documented codes

47with documented causes

Weil-McLain boiler with the fault code shown on the display

Quick Answer

Weil-McLain heating appliances display 48 documented error codes. Each code below opens its own page with the official meaning, the documented causes, the safety assessment and the parts involved.

All Weil-McLain Error Codes

48 codes, each with its own page. Click a code to open the meaning, the documented causes and the repair.

Code	What it means
AIR PRESSURE Switch Open	Occurs when Air Pressure connection is open
Auto Reset Count	Records number of lockouts that have automatically reset since this count was last cleared
BLOWER FAULT	Blower unable to reach required speed or does not reach 0 RPM when turned off
Blower Fault 1	Blower does not reach zero RPM within four minutes when mode is Standby or Prepump
Blower Fault 2	Blower unable to reach required pre-purge speed or ignition speed Blower failed to complete calibration…
Blower Fault 3	Blower is outside of minimum or maximum speed for 10 seconds
Blower Fault 4	Blower drops to zero RPM while burner is firing
Boiler Output Sensor Flue Sensor	Occurs if dual temperature sensors values have spread by more that 10ºF
Clock Fault	When the real time clock chip cannot be read
Closure Switch Fault	Closure switch connections on P7 Pins 2 and 3 are open for more than 4 minutes
Closure Switch fault	Proof of Closure connections on J18, Pins 2 and 3 are open
Communication errors	Occurs if display or main control communications is out for 30 seconds
Configuration fault	Configuration data in the control safety micro does not match data in the control’s application micro
Control Fault	Records number
Control fault	Occurs when micro- controllers on main board have a RAM or ROM error
DISPLAY COMM Fault	Occurs if display communications out for 30 seconds
EXP BOARD COM FAULT	Expansion Control Board communication fault
FALSE FLAME	Occurs if flame is detected when there should be no flame
FLAME FAULT	Occurs if flame is detected when there should be no flame
FLAME LOSS FAULT	Flame value dropped below the allowable Proof of Flame threshold while running
FLUE TEMP TOO HIGH	Occurs if flue temperature sensor exceeds 210ºF (Warning) or 220ºF (Lockout)
Flame Circuit Fault	When the digital flame input does not sense that the circuit discharged appropriately
Flue Temp Too High	Occurs if flue temperature sensor exceeds 210°F (Warning) or 220°F (Lockout)
GAS PRESSURE SW FAULT	Gas pressure switch is open (high or low)
GAS RELAY FAULT 1-4	The control has detected a problem with the control board’s gas valve output circuit
GV FAULT EXPANSION BRD	Gas valve output of the Expansion module
HIGH TEMP LIMIT	Boiler temperature sensor reached High Temp Limit setting (no higher than 200° F)
HW FAULT EXPANSION BRD	Expansion Control Board hardware has failed
Hardware Fault	Occurs when micro-controllers on main board have a RAM or ROM error, or communication is cut off
Hardware Fault X	The control has detected a problem with its gas valve output circuit
IGNITION 1 FAULT	Boiler went through two ignition attempts and either never detected flame, or flame sense value never reached…
IGNITION 2 FAULT	Boiler went through two ignition attempts and did not meet running flame threshold for boiler model within 10…
IGNITION FAULT	Boiler went through 5 ignition attempts and never detected flame or flame sense value never reached minimum…
Ignition Retries	Displays the number of ignition attempts in the current ignition sequence
Internal Clock Fault	Occurs when the internal clock of the control is out of sync
LIMIT OPEN	Occurs if manual or automatic reset limit opens
LOW FLAME SHUTDOWN	Flame quality dropped below allowable Running Flame Threshold, but it did not go out
LOW WTR CONDITION	Occurs if the integrated LWCO sees no water
Lockout History 1	Details of present or last recorded lockout
Lockout History 2	Details of boiler during the second oldest lockout still in memory
Lockout History 3	Details of boiler during the oldest lockout still in memory
MINIMUM AIR FLOW SWITCH FAULT	Min air flow switch is open when it should be closed, or closed when it should be open
Manual Reset Count	Records number of lockouts that required a manual reset since this count was last cleared
OUTDOOR SENSOR ERROR	Outdoor temperature sensor short or OPEN
Outdoor Sensor Error	Outdoor temperature sensor is short or open
PS Fault Exp. Board	Pressure switch issue detected on expansion board
SUPPLY WATER TEMPERATURE TOO HIGH	Occurs when the System Supply temperature goes above 200º F when the burner is running
Software Incompatible	Main control and display software are not compatible

What Fails Most Often on Weil-McLain

Grouped from the official meaning of each of the 48 codes above — not from opinion. The number is how many different fault codes point at that component.

Component	Codes	Examples
Ignition	8	FLAME FAULT, FLAME LOSS FAULT, Flame Circuit Fault, IGNITION 1 FAULT
Control Board	6	Control fault, EXP BOARD COM FAULT, GAS RELAY FAULT 1-4, HW FAULT EXPANSION BRD
Fan	5	BLOWER FAULT, Blower Fault 1, Blower Fault 2, Blower Fault 3
Temperature Sensor	4	Boiler Output Sensor Flue Sensor, HIGH TEMP LIMIT, OUTDOOR SENSOR ERROR, Outdoor Sensor Error
Pressure Switch	3	AIR PRESSURE Switch Open, GAS PRESSURE SW FAULT, MINIMUM AIR FLOW SWITCH FAULT
Communication	3	Communication errors, DISPLAY COMM Fault, Software Incompatible
Flue	2	FLUE TEMP TOO HIGH, Flue Temp Too High
Gas Valve	2	GV FAULT EXPANSION BRD, Hardware Fault X

Parts & Prices

Search Weil-McLain replacement parts…

The parts most often involved in the Weil-McLain faults listed above.

Ignition / spark electrode

OEM Part · Weil-McLain

Check price View price

PCB (printed circuit board)

OEM Part · Weil-McLain

Check price View price

Fan / blower assembly

OEM Part · Weil-McLain

Check price View price

Temperature sensor (NTC)

OEM Part · Weil-McLain

Check price View price

Compatible Ignition / spark electrode

Compatible · Generic

Check price View price

Compatible PCB (printed circuit board)

Compatible · Generic

Check price View price

Compatible Fan / blower assembly

Compatible · Generic

Check price View price

Compatible Temperature sensor (NTC)

Compatible · Generic

Check price View price

Reconditioned Ignition / spark electrode

Used / Tested · Weil-McLain

Check price View price

Reconditioned PCB (printed circuit board)

Used / Tested · Weil-McLain

Check price View price

Reconditioned Fan / blower assembly

Used / Tested · Weil-McLain

Check price View price

Reconditioned Temperature sensor (NTC)

Used / Tested · Weil-McLain

Check price View price

View All Weil-McLain Parts →

Prices and availability vary by region and are shown by the retailer, not by TroubleAtlas.

Diagnostic Tools

What an engineer uses to work through the codes on this page.

Digital Multimeter (TRUE RMS)

For testing electrode resistance and PCB voltages

$35–$80 View price

Gas Leak Detector

Essential for checking connections after any gas valve work

$25–$45 View price

Manometer / Pressure Gauge

To measure gas inlet and burner pressure

$40–$90 View price

Combustion Analyzer

For verifying flue gas readings after repair

$180–$350 View price

Shop all diagnostic tools →

TroubleAtlas Pro

For HVAC Professionals

Get cited by AI. Get found by customers.

TroubleAtlas Pro puts your business in front of homeowners searching for Weil-McLain faults, and structures your listing so AI assistants can cite you as a trusted source.

Explore TroubleAtlas Pro →

Considering a New Heating System

Considering a New Heating System?

If your Weil-McLain appliance is over 10 years old, replacing it with a modern condensing boiler or air-source heat pump could cut energy bills and remove the recurring faults listed on this page.

Compare Heating System Prices →

Professional heating system installation and service

YouTube Channel

TroubleAtlas · on YouTube

Watch the fixes. Follow the channel.

Step-by-step boiler repair guides, equipment reviews and heating system comparisons from qualified engineers.

New fixes every week

Subscribe on YouTube →

Weekly

Fix in 5

Quick fixes for common boiler faults explained in under 5 minutes

Head-to-Head

Boiler Comparator

Side-by-side comparisons of popular boiler models

Scored

Boiler Reviews

Independent reviews with TroubleAtlas Score ratings

Find a Specialist

Find help near you

Don’t fix it alone. Find a trusted heating engineer near you.

TroubleAtlas connects you with vetted local heating professionals who can inspect, diagnose and repair your Weil-McLain appliance safely — no guesswork, no unnecessary call-outs.

VettedNear youDirect contact

Are you a professional? Join our network →

Suggested engineer · your city Certified heating technician

Local heating professionals are coming to your area

We’re onboarding Gas Safe registered and licensed HVAC engineers city by city. Check back soon, or search above to see current availability.

Written by TroubleAtlas Technical Team · Last updated: 2026-08-02 · Sources: manufacturer service documentation · How we verify