Weil-McLain boiler troubleshooting

Weil-Mclain was founded in the 1881 in Chicago, United States. It offers a wide range of boilers. Originally, it was a small plumbing and heating house. Now the company is a leading developer and manufacturer of heating systems. The company sees its mission in the design and manufacture of comfortable equipment and maintaining a leading position in the market. Below you will find boiler Mclain-Weil, troubleshooting system in the form of a table.

Weil-McLain Gold GV 3 Series boiler troubleshooting

SymptomCommon CausesPossible Corrections
Rapid cycling — boiler turns on and off frequentlyThermostat installed where drafts or heat affect readingLocate thermostat on inner wall away from heat sources or cool drafts.
Heat anticipator in thermostat adjusted incorrectlyAdjust thermostat per manufacturer's instructions.
Incorrect limit settingSet limit according to system needs. Maximum setting is 220* F. Increase limit setting to decrease cycling.
Insufficient water flow through boilerCheck all valves to and from boiler. Return to proper setting.
Confirm circulator size.
Frequent release of water through relief valveExpansion tank sized too smallCall qualified service technician to check expansion tank operation and size.
Flooded expansion tankCall qualified service technician to check expansion tank operation.
Inoperative limit controlCall qualified service technician to replace limit control.
Need to frequently add makeup waterLeaks in boiler or pipingHave qualified service technician repair leaks at once to avoid constant use of makeup water. Makeup water can cause mineral deposits which, in turn, can cause boiler section failure. Do not use petroleum base stop-leak compounds.
Black water conditionOxygen corrosion due to leaks in boiler and pipingHave qualified service technician repair at once. Keep pH of water between 7.0 to 8.5.
Popping or percolating noise heard in boilerMineral deposits in sections due to constant use of makeup waterCall qualified service technician to de-lime boiler, if necessary. In some cases, deposits will be too heavy to remove with de-liming procedures.
Have qualified service technician repair leaks to eliminate need for constant makeup water.
Incorrect pH of boiler waterCall qualified service technician to check pH level and correct. pH should be maintained between 7.0 to 8.5.
Insufficient water flow through boilerCheck all valves to and from boiler. Return to proper setting.
Confirm circulator size.
Metal flakes found in vent outlet or vent starter tee — flue way corrosionContaminated combustion air supplyRemove any contaminating products.
Provide outside air for combustion. Kit available through Weil-McLain distributor. Have qualified service technician pipe-up kit.
Condensation of combustion gases in boiler sectionsHave qualified service technician check operation of mixing system. Repair/replace if necessary.
Some radiators or baseboard units do not heat or are noisyAir in systemBleed air from system through air vents in radiators or baseboard units.
Low system pressureFill to correct pressure.
Check for leaks in boiler or piping. Have qualified service technician repair at once.
High limit set too lowAdjust high limit to higher setting.

Weil-McLain ULTRA ULTRA-105 boiler troubleshooting

Boiler not firing and:Check for:Solution:
Display first digit shows a number from 1 to 8. Last digits show 2 or 3-digit number (boiler outlet water temperature).This is normal operation.Boiler is in normal operating mode.
Display first digit shows the number 6; other 2 or 3 digits show boiler water temperatureBoiler water temperature may have exceeded limit — the boiler will restart after the water temperature has dropped below limit setting (parameter 4) minus the differential.If boiler water temperature is above parameter 4, the boiler shut down on limit.
Follow the same corrective action suggestions given for Code 18.
The control module may have lost flame signal — if so, boiler should restart.If the boiler water temperature is NOT above parameter 4, the control may have lost flame signal. Flame signal (DC volts from low voltage terminal strip terminal 9 to ground) should be at least 4 VDC.
Verify adequate gas flow — check incoming gas pressure. If acceptable, check gas line size, gas regulator or any possible cause of reduced pressure.
A lower flame signal may indicate a fouled ignitor or damaged ignitor insulation. Follow procedure in Ultra Boiler manual to check ignition electrode wiring and inspect and clean the ignition electrode. Replace the ignition electrode and wiring if necessary.
If problem persists, obtain a maintenance kit for the boiler and follow the maintenance procedure beginning
Display flashes 9, then b. Last two digits show code number.Display is showing a lockout code.
Control display is blankIs 120 vac present at terminals 1 and 2 of line voltage terminal strip?If not, check external line switch and fuse or breaker.
Blower running on high, and F1 fuse blown?Turn power off to boiler. Remove power wiring to circulator(s) at boiler terminal strip. Replace the FI fuse. Then turn power on to boiler. If blower stops running and display works properly, replace defective circulator(s) and retry.
If the blower continues to run after checking step 2, above, turn power off to the boiler. Inspect wiring and high voltage terminal strip for defects. Replace if necessary. Then retry.
If the problem persists after above steps, replace the control module.
Display shows U124 or U125Display stays on U124 or U125Check transformer. If good:
• Turn off power to the boiler.
• Disconnect thermostat wires at boiler.
• Replace F3 fuse.
• Determine cause of fuse failure on 24-volt system.
• Replace defective part and retry.
If problems persists, check low voltage terminal strip and wire harness. Replace if necessary. Retry.
If problem persists, replace control module.
Display first digit shows 0 and last digits show 2 or 3-digit number (boiler outlet water temperature).Are room thermostat and DHW aquastat satisfied?If yes, then boiler should be off — there is no call for heat. Turn up thermostat or aquastat. Boiler should start.
Is room thermostat or DHW aquastat calling for heat?Check parameters 2 and 3.
• To change to Parameter mode, press the MODE button one time when in Standby mode.
• Parameter 2 must be ON for DHW operation — [2 01] on display.
• Parameter 3 must be ON for central heating operation — [3 01] on display.
• Refer to instructions in this guide to set parameters.
Does display intermittently show 0 for outlet water temperature?Check parameters 1 and 3.
• To change to Parameter mode, press the MODE button one time when in Standby mode.
If parameter 1 shows 68:
• Press “+” until display returns to 140.
• Then press “Store.”
• Display will blink when setting is accepted and stored.
If parameter 3 shows 00:
• Press “+” and display will return to “01”
• Then press “Store.”
• Display will blink when setting is accepted and stored.
If problem persists, replace the control module.
Is blower running on low?From Standby mode, press “Mode” twice and display will change to “Info”
• Press “Step” until display shows #6.
• If #6 value displays as 32, replace the blower assembly.
Is room thermostat or DHW calling for heat, but boiler is not firing?Check thermostat or aquastat:
• Turn off power to the boiler.
• Install a temporary jumper on low voltage terminal strip terminals 5 and 6 for central and terminals 3 and 4 for DHW.
• Retry. If boiler operates, check the thermostat or aquastat and connect wiring. Replace if necessary.
• Remove jumper and retry.
Check boiler wiring:
• Turn off power to the boiler.
• Check wiring against wiring diagram. Verify all wiring is in good condition and securely fastened.
• Replace harness if necessary and retry.
If boiler still does not fire, replace the control module.

Weil-McLain WGO boiler troubleshooting

Common ProblemsCommon CausesPossible Corrections
Rapid cycling — burner turns on and off frequently.Thermostat installed where drafts or heat affect reading.Locate thermostat on inner wall away from heat sources or cool drafts.
Heat anticipator in thermo- stat adjusted incorrectly.Adjust heat anticipator to match current draw.
Incorrect limit setting.Have qualified service technician increase limit setting to decrease cycling. Maximum setting 220° F.
Need to frequently add makeup water.Leaks in boiler or piping.Have qualified service technician repair leaks at once to avoid constant use of makeup water.
Popping or percolating noise heard in boiler.Mineral deposits in sections due to constant use of make- up water, or incorrect pH.Have qualified service technician de-lime boiler, repair leaks at once to avoid constant use of makeup water and check pH (between 7.0 and 8.5).
Black water condition.Oxygen corrosion due to leaks in piping.Have qualified service technician repair leaks at once to avoid constant use of makeup water and check pH (between 7.0 and 8.5).
Frequent release of water through relief valve.Expansion tank sized too small or water-logged.Have qualified service technician check expansion tank operation.
Metal flakes found in flue way.Contaminated combustion air supply.Remove sources of hydrocarbons in or near boiler area. (Bleaches, cleaners, chemicals, sprays, fabric softeners, paint remover, etc.)
Condensation of combustion gases.Have qualified service technician check boiler operation.
Some radiators or baseboard units do not heat or are noisy.Air in system.Bleed air from system through air vents in radiators or baseboard units.
Low system pressure.Have qualified service technician check for leaks in boiler or piping at once.
High limit set too low.Have qualified service technician adjust limit to higher setting.
Domestic water from tankless heater is hot then suddenly turns cold.
OR
Domestic water from tankless heater is always lukewarm.
Mineral deposits insulate internal waterways of heater.Have qualified service technician delimit or replace coil.
Boiler stop-leak compound has been added to boiler wa- ter and is insulating outside of coil.Have qualified service technician remove and clean coil and drain, and flush boiler to remove stop-leak.
Incorrect mixing valve setting for tankless heater.Have qualified service technician adjust mixing valve setting.
Domestic flow rate too high.Have qualified service technician install flow check valve set to rating of tanldess heater.
Incorrect setting on tankless heater control.Have qualified service technician raise tankless control setting. Adjust differential on tankless control to lower setting.

Weil-McLain WM97 boiler troubleshooting

DisplayConditionDiagnosticsCorrective Action(s)
Nothing shown on display screen and boiler will not respond to call for heatControl is not receiving 24V powerCheck wiring for short circuit or incorrect wiring.Correct wiring per wiring diagram including connection of transformer to the control module.
Check 3-amp low voltage fuse on control module shown Replace fuse with proper part. If fuse blows again recheck wiring per diagram.
Check transformer connection to the control module per wiring diagram. Check for 24V output of transformer.Replace transformer if it is is receiving 120Vac, but not outputting 24Vac.
Nothing is shown in display screen and no other boiler components are operatingControl is not receiving 120V powerCheck service switch and/or circuit breaker to boiler turned is on.Turn on service switch to power boiler.
Is there 120 Volts at the service switch?Troubleshoot and correct the power supply to the senesce switch.
Is the WM97+'s ON/OFF POWER SWITCH located on top of the boilerTurn the WM97+'s power switch to ON.
Check for 120 volts at the line voltage terminal block located inside the top left electrical compartmentCorrect wiring inside the control pod using the wiring diagram in this manual.
Inspect 12-amp fuse. Replace if necessary.Replace the fuse with proper part. If fuse blows again recheck wiring per diagram.
Nothing is shown on display screen, but boiler is operatingOccurs when the communication is lost from the control module to the display.Check for loose connections and proper pin alignment/ engagement on the control module's plug P9 and the back of the display circuit board.Check for continuity on the wire harness from the display to the control module.
Cycle power off and on using boiler power switch and check for operation.Replace with new display module.
TEMP RISE TOO QUICKLYOccurs when supply water temperature in heat exchanger rises faster than 2°F per second during the first two minutes the burner is on.Automatically resets after 1 minute delay or using manual reset on display. Manual reset is necessary after 5 automatic resets have occurred during the same Priority heat demand. Reset using manual reset screen on displayVerify water pipe is installed correctly.
Verify proper circulator and speed for boiler size and system requirements.
See message displayed TEMPERATURE SENSOR and follow procedure for loose connections.
SUPPLY 58F RETURNBoiler Out temperature has exceeded the Boiler In temperature by more than 58°FAutomatically resets after 30 second delay or using manual reset on display.Verify water pipe is installed correctly.
Verify proper circulator and speed for boiler size and system requirements.
See message displayed TEMPERATURE SENSOR and follow procedure for loose connections.
RETURN > SUPPLYOccurs when a return water temperature rs greater than the corresponding supply temperature by 10°F or more.Automatically resets when condition no longer exists.Verify proper flow direction of the boiler circulator. This circulator must be installed to push water through the boiler's return pipe. Verify proper boiler circulator speed setting in the control module.
TEMPERATURE SENSOROccurs wtien a temperature sensor has electrically shorted (SHORT) or has become disconnected (OPEN).Will automatically reset if the condition clearsCheck all the temperature readings of the boiler on the DIAGNOSTICS - TEMPERATURES menu to determine if any sensors are currently displayed as SHORT or OPEN. Compare this to the boiler temperatures recorded in the DIAGNOSTICS - ERRORS - LOCKOUT HISTORY # - TEMPERATURES during the last several lockout conditions. Determine which sensors are suspect and measure their resistance value. If the resistance values are incorrect replace the temperature sensor. OUTDOOR TEMP is the optional outdoor air temperature sensor. If this are not being used they will always be shown as OPEN. This is normal unless the sensors were installed.
Check wire harness for loose connections and pin engagement at sensor connection, chassis mount connection through control housing, and the control module. Unplug connection at sensor and at control module and check continuity between ends.
If problem persists after checking items above replace control module. Refer to repair pans section for kit number.
Occurs wtien dual temperature sensors values have spread by more that IO°F if the burner is onAutomatically resets when sensors are within 10°F.Follow procedure for above for SHORT and OPEN sensor conditions to properly diagnose sensor. If measured resistance values of sensors convert to temperatures separated by more than 10°F replace the sensor.
FLUE TEMP TOO HIGHOccurs wtien flue temperature sensor exceeds 216°FAutomatic reset occurs if temperature drops below 216°F for 2.5 minutes. Manual reset is required if the temperature rises above 225°F. Reset using manual reset screen on displayFollow procedure for above for SHORT and OPEN sensor conditions to properly diagnose sensor. In addition inspect heat exchanger combustion chamber and flue ways for abnormal wear or buildup.
Inspect vent system for abnormal wear or damage.
Contact Weil-McLain Technical Support.
LOW WTR CUTOFF OPENOccurs written internal low water cutoff contacts openAutomatic reset occurs if contacts are open at least one second, but less than 5 seconds. Manual reset of control module if contacts are open longer than 5 secondsCheck for low water condition in system. If low water condition does not exist, check Diagnostics - Inputs screen to view status of Low Water Cutoff. If shown as OPEN check wiring between LWCO and control module.
DISPLAY COMMOccurs when display communications out for 30 secondsAutomatically resets when communication is re- established.Check for a loose connection at the index plug on the control and connection on the back of the display.
LIMIT OPENOccurs when manual or automatic esetl imitop ens.Automatic external limit will reset 2.5 minutes after external limit device closes. Manual limit fault must be reset by choosing Reset Lockout on the display.Is there an external safety device connected? If ye% trouble shoot the external limit to determine and correct the cause that opened the limit. Also check for loose wiring connections.
Remove the top right electrical cover and inspect the connector. Ensure a jumper is installed across the MAN LIMIT terminals if not using a manual reset external limit. Ensure a jumper is installed across the AUTO LIMIT terminals if not using a automatic reset external limit.
HIGH TEMP LIMITBoiler temperature sensor reached High Temp Limit setting (no higher than 200°F)Reset using manual reset screen on displayVerify all isolation valves are open and circulators are programmed into the control module properly. The internal boiler circulator can be configured to turn on or off with DHW and heating zones. Refer to the control module Setup section to configure these properly for the system.
Verify water pipe is installed correctly per instructions in this manual.
Verify proper circulator sizing for boiler size and system requirements.
See message displayed TEMPERATURE SENSOR and follow procedure for loose connections.
FLAME FAULTOccurs when flame is detected when there should be no flameReset using manual reset screen on displayBurner may be operating too hot due to incorrect combustion. Inspect flame and conduct combustion test. Force boiler into hi-fire. Check flue gases with combustion analyzer and correct using the maintenance an startup procedure in this manual.
Verify FLAME SIGNAL value quickly goes to zero on the DIAGNOSTICS - INPUTS screen when the gas valve closes.
Check for flame at burner via flame current with burner off. Turn boiler off and watch flame through observation port. If flame continues after shutdown replace gas valve and venture.
GASVALVE FAULTThe control module has detected a problem with it gas valve output circuitControl will do automatic retry; lockout if retry unsuccessful; retry 1 hour after lockout — restart if condition cleared, but lockout permanently if condition still present. Requires manual reset if control is in lockoutCheck wire harness connections between gas valve and control module.
Check resistance between control and gas valve.
If lockout reoccurs replace control module.
BLOWER FAULTBlower unable to reach required speed or does not reach 0 RPM when turned off. NOTICE: The blower will not rotate without a low voltage signal. Unplugging the low voltage blower wire harness will not allow or cause the boiler to rotate.Reset using manual reset screen on display; control module will check again after 1 hour and will automatically restart if condition is correctedCheck wire harness for loose connections and pin engagement at blower connections, chassis mount connection through control housing, and control module. Unplug connection at blower and at control module and check continuity between ends. Blower is connected to both low voltage and line voltage harness.
Check Diagnostics - Inputs screen with boiler in standby mode and blower not running. If BLOWER SPEED is not 0 RPM then replace blower.
If blower does not rotate during ignition sequence check for 120V power at blower connection. If 120Vac power at blower motor and it doesn't start replace blower. Check power at control module. If 120Vac is not present at control module when boiler is powered replace control module.
IGNITION FAULTBoiler went through 5 ignition attempts and never detected flameAutomatically resets after 1 hour or can be reset by performing manual reset on boiler.Check condensate trap for blockage allowing condensate to accumulate inside heat exchanger. Check ignition cable connection.
Fouled, worn, bent, or faulty igniter. Fouled igniters can be cleaned for additional use with fine grit sand paper or steel wool. Worn or badly fouled igniters should be replaced with the proper repair part. Igniter rods should be parallel with a 35mm (0.138in) spark gap.
Dirty burner and/or heat exchanger will cause high back pressure and poor ignition. Follow procedure in maintenance section of this manual to clean burner and heat exchanger using flue cleaning tool and rinse method.
Visual inspection of flue ways will often will not be able to diagnose condition.
Check combustion settings on high and low fire and adjust per setup instructions if necessary.
Check incoming gas pressure with boiler off and at high fire. Adjust within limits on rating label.
Verify correct boiler model is selected in control and high altitude is selected for installations 5500ft above sea level.
Check ignition cable resistance. Should measure 1000 Ohms (+/- 50 Ohms)
Check for flue pipe and intake pipe restrictions or blockage
Check burner fasteners and gaskets
Check venturi gaskets and proper propane orifice bushing
Check condensate trap for blockage allowing condensate to accumulate inside heat exchanger