Laars Boiler Error Codes — Meanings, Causes & Repair in Greater Vancouver

Seeing a fault code on your Laars boiler? This guide explains what the most common Laars boiler error codes mean, what’s safe to check yourself, and when to call HeatLand’s licensed, TSBC-certified gas technicians for Laars boiler repair across Metro Vancouver and the Fraser Valley.

The codes below apply across common Laars models (Mascot FT, Mascot LX, NeoTherm, Endurance). Meanings follow Laars’s documented fault codes — always confirm against your unit’s own manual, because exact wording can vary by model, control board and firmware.

How to read Laars boiler error codes

Laars uses several different controllers depending on the model and generation, so the fault-code format varies by series. (1) MASCOT FT (combi/heat-only, MFTCW/MFTHW/MFTCH): a 2-digit NUMERIC fault code (e.g. 10, 11, 16, 20, 28, 32, 33) shown on the display, with faults classed as 'Hard Lock' (requires manual reset via the power button after the fault is corrected) or 'Soft Lock' (auto-clears when the condition clears, e.g. when temperature drops). (2) MASCOT LX: the SIT/Laars controller shows 'E0xx' LOCKOUT codes (E001-E019) plus 'Nxx' NOTIFICATION codes (N01-N06, non-locking) on a graphical display; a lockout is cleared with the Reset button after the underlying problem is fixed. (3) NEOTHERM (NTV/NTH) and other Laars boilers using the Honeywell SOLA control: a NUMERIC code is shown on the operator interface with the word 'Lockout' or 'Hold' in the lower-left of the display; codes are tagged L (Lockout – needs a manual Reset) or H (Hold – clears automatically when the condition clears). Write down the number and look it up; press Reset to clear a lockout. (4) ENDURANCE (EBP/EDP): the boiler control shows letter codes 'F1/F3/F4/F5/F6/F8', plus 'LO' (lockout), 'OFF', and 'ICE'; it flashes the code and then shows the supply temperature. The ignition control adds LED FLASH codes (e.g. 2 flashes = erroneous flame signal, 3 flashes = ignition control lockout).

Laars boiler error codes & what they mean

These are the Laars boiler codes our Greater Vancouver technicians see most. Anything marked pro repair involves gas, electrical, sealed-combustion or control-board work that must be done by a licensed gas technician (TSBC-certified in BC) — never open gas or electrical components yourself.

Code	What it usually means	Common causes	Safe to check yourself
10	Flame has extinguished 8 (eight) times – hard lockout. The burner repeatedly lost its flame during operation pro repair	Low or fluctuating gas pressure (should be 3.5-14 in. WC); Gas valve or gas-valve wiring problem; Dirty or failed flame-detection sensor	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work (so gas is on); Check the condensate drain/trap is not clogged or frozen
11	Ignition has failed 10 (ten) times – hard lockout. The boiler tried and failed to establish flame the maximum number of times pro repair	Gas supply off or low gas pressure (3.5-14 in. WC); Air in the gas line after service; Dirty or failed igniter / ignition transformer	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Check the condensate drain/trap is clear
16	Operating temperature sensor detects water temperature greater than 203 degrees F (95 degrees C) – hard lockout (overheat) pro repair	Circulator/pump not running or air-bound system; Low system water pressure / inadequate flow; Blockage at the central-heating (CH) inlet	Check the system pressure gauge is in the normal range (typically about 12-25 psi cold); Confirm heating-system valves are open; Let the boiler cool, then press the power/reset button once
20	Condensate fault – the condensate switch is open when it should be closed (condensate drain/trap problem) – hard lockout pro repair	Clogged or frozen condensate trap/hose; Condensate hose kinked or improperly routed; Blocked vent causing condensate backup	Check the condensate drain line and trap for clogs, kinks, or ice; Make sure the condensate hose runs downhill to the drain; After clearing, press the power/reset button once
28	Overheat sensor open or short – soft lock. A wiring or sensor fault on the overheat/limit sensor circuit pro repair	Loose or damaged sensor wiring/connector; Sensor out of resistance range; Failed overheat sensor	Allow the boiler to cool; soft-lock codes clear when temperature decreases; Press the power/reset button once if it does not self-clear
32	DHW (domestic hot water) sensor open or short – soft lock pro repair	Loose or damaged DHW sensor wiring/connector; DHW sensor out of resistance range / failed sensor	Press the power/reset button once; Note that central heating may still operate while only DHW is affected
33	CH (central heating) temperature sensor open or short – soft lock pro repair	Loose or damaged CH sensor wiring/connector; CH sensor out of resistance range / failed sensor	Press the power/reset button once
E001	Memory error lockout – a problem with the EEPROM memory in the control unit pro repair	Control board (SIT control) EEPROM fault; Power disturbance / brownout	Press the Reset button to try to cancel the lockout; Power the unit down, wait two minutes, then power on again
E002	Fan speed error – lockout because the fan (blower) did not reach normal speed pro repair	Blockage in the vent; Wiring problem to the blower; Seized or failing blower motor	Check that the outdoor vent terminals are clear of snow, ice, leaves, or debris; Press the Reset button once
E003	Flame present when not expected (not in Run) – lockout because the controller detected a flame while the unit was not firing pro repair	Flame-sensor wiring fault; Failed flame sensor; Control board fault	Press the Reset button once
E004	Outlet auto-reset high limit – lockout because the water outlet temperature sensor reported too high a temperature pro repair	Low flow / pump not circulating; Low system water pressure; Outlet temperature sensor wiring or sensor fault	Check the system pressure gauge is in the normal range; Let the boiler cool, then press the Reset button once
E005	Water pressure switch error – lockout due to a problem with the water pressure switch (switch will not close unless at least 5 psi of water pressure is present) pro repair	Low system water pressure (below ~5 psi); Water pressure switch wiring fault; Failed pressure switch	Check the system pressure gauge – if low, the system may need refilling by a technician; Press the Reset button once after pressure is restored
E007	Low water cutoff error – lockout because the optional low water cutoff switch reported a low-water condition or is open pro repair	Low water level in the system; Low water cutoff switch wiring fault; Failed low water cutoff switch	Check the system pressure gauge for a low-water/low-pressure indication; Press the Reset button once after water level is restored by a technician
E008	Field interlock error – indicates a problem with the control circuits outside the boiler (external interlock chain) pro repair	External safety/interlock device tripped; Wiring problem in the field interlock circuit; Control board fault	Press the Reset button once
E009	Blocked vent switch – lockout because the controller did not detect normal airflow through the system pro repair	Blockage in the vent or air intake; Air pressure switch wiring fault; Failed air pressure switch	Check the outdoor vent and intake terminals are clear of snow, ice, or debris; Press the Reset button once
E010	Blocked vent / fan-proving switch error – lockout because the controller did not detect normal airflow (air pressure switch open / not enough air moving) pro repair	Blockage in the vent or air intake; Air pressure switch wiring fault or failed switch	Check the outdoor vent and intake terminals are clear; Press the Reset button once
E011	Flame loss lockout – the controller detected three consecutive flame losses while the unit was trying to run pro repair	Flame sensor dirty or failed; Gas valve wiring problem; Gas supply problem / low gas pressure	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press the Reset button once
E012	Lockout due to three consecutive failed ignitions – the boiler could not establish flame on three tries pro repair	Gas supply off or low gas pressure; Air in the gas line; Dirty or failed flame sensor / igniter	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press the Reset button once
E013	Flue high temperature – the flue sensor reported a temperature above 195 degrees F pro repair	Blocked flue; Flue safety sensor wiring fault; Failed flue sensor/switch	Check the outdoor flue/vent terminal is clear of obstruction; Let the boiler cool, then press the Reset button once
E014	Outlet high temperature (manual-reset high limit) – the system reached the high limit and locked out pro repair	Blocked flue; Low flow / pump not circulating; Outlet water temperature sensor wiring or sensor fault	Check the system pressure gauge is in the normal range; Let the boiler cool, then press the Reset button once
E015	Flue sensor drift too high – the dual flue sensor's two elements disagree by more than the allowed amount pro repair	Flue sensor wiring fault; Failed dual flue sensor	Press the Reset button once
E016	Outlet sensor drift too high – the dual outlet sensor's two elements disagree by more than the allowed amount pro repair	Outlet water temperature sensor wiring fault; Failed dual outlet sensor	Press the Reset button once
E017	Flue sensor error – a fault with the flue sensor pro repair	Flue sensor wiring fault; Failed flue sensor	Press the Reset button once
E018	Outlet sensor error – the water outlet temperature sensor has failed pro repair	Outlet water temperature sensor wiring fault; Failed outlet sensor	Press the Reset button once
E019	Inlet sensor error – a fault with the inlet water temperature sensor pro repair	Inlet water temperature sensor wiring fault; Failed inlet sensor	Press the Reset button once
N05	Notification (non-locking): Domestic hot water sensor not present – the DHW sensor is disconnected or not working. If the condition continues, the controller will present a lockout pro repair	DHW sensor disconnected; DHW sensor wiring fault or failed sensor	No homeowner action beyond noting that hot-water performance may be affected; a technician should check the sensor
N06	Notification (non-locking): Outdoor temperature sensor not present – the outdoor sensor is disconnected or not working; the boiler reverts to a fixed setpoint (140 degrees F or parameter P62, whichever is lower) pro repair	Outdoor sensor disconnected; Outdoor sensor wiring fault or failed sensor	No homeowner action; the boiler keeps running on a fixed setpoint until a technician checks the outdoor sensor
47	Flame rod to ground leakage (Hold) – the controller detected a leakage path on the flame-rod circuit pro repair	Cracked or contaminated flame rod / insulator; Moisture or carbon tracking on the flame-rod assembly; Wiring fault to the flame rod	This is a 'Hold' that may clear on its own when the condition clears; if it persists, a technician is required
61	Anti short cycle (Hold) – the control is enforcing an anti-short-cycle delay; this is a normal hold, not a lockout DIY-checkable	Normal protective delay between burner cycles; Frequent on/off demand	No action needed – the boiler resumes automatically after the delay
62	Fan speed not proved (Hold) – normal during startup; the control is waiting for the fan to reach the required speed pro repair	Brief, normal startup condition; Vent blockage if it persists; Blower wiring or blower fault if persistent	If persistent, check the outdoor vent/intake terminals are clear of debris or ice
63	LCI (Limit Control Input) off (Hold) – a device in the limit/safety interlock chain is open pro repair	A safety limit in the interlock chain has opened; Interlock-chain wiring fault	No homeowner action – a technician must check the limit/interlock chain
79	Outlet high limit (Hold or Lockout) – the water outlet temperature reached the high-limit threshold pro repair	Low flow / pump not circulating; Low system water pressure; Outlet limit/sensor wiring or device fault	Check the system pressure gauge is in the normal range; Let the boiler cool; if it is a lockout, press Reset once
80	DHW (domestic hot water) high limit (Hold or Lockout) – the DHW temperature reached the high-limit threshold pro repair	Low flow through the DHW circuit; DHW limit/sensor wiring or device fault	Let the boiler cool; if it is a lockout, press Reset once
81	Delta T limit (Hold or Lockout) – too large a difference between inlet and outlet water temperatures pro repair	Insufficient flow (pump not running, air-bound, valve closed); Inlet or outlet sensor fault; Undersized or restricted piping	Check the system pressure gauge is in the normal range; Confirm heating-system isolation valves are open; If it is a lockout, press Reset once
82	Stack limit (Hold or Lockout) – the flue/stack temperature reached its limit pro repair	Blocked flue / vent; Stack high-limit switch wiring or device fault; Heat-exchanger fouling	Check the outdoor flue/vent terminal is clear; If it is a lockout, press Reset once
91	Inlet sensor fault (Hold) – the inlet water temperature sensor circuit is faulty pro repair	Inlet sensor wiring fault; Failed inlet sensor	No homeowner action – a technician should check the sensor
92	Outlet sensor fault (Hold) – the outlet water temperature sensor circuit is faulty pro repair	Outlet sensor wiring fault; Failed outlet sensor	No homeowner action – a technician should check the sensor
100	Pressure sensor fault (Hold) – a fault on the (air/gas) pressure sensor circuit pro repair	Pressure sensor wiring fault; Failed pressure sensor	No homeowner action – a technician should diagnose the pressure sensor
105	Flame detected out of sequence (Hold or Lockout) – flame was sensed at a time the control did not expect it pro repair	Flame-sensing circuit fault; Gas valve leaking through; Control fault	If it is a lockout, press Reset once
106	Flame lost in MFEP (Main Flame Establishing Period) – lockout because flame was lost while the main flame was being established pro repair	Low or unstable gas pressure; Dirty or failed flame sensor; Gas valve fault	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press Reset once
107	Flame lost early in run – lockout because flame was lost shortly after the run began pro repair	Low or unstable gas pressure; Dirty or failed flame sensor; Venting / combustion-air problem	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press Reset once
108	Flame lost in run – lockout because flame was lost during normal running pro repair	Low or fluctuating gas pressure / gas supply problem; Dirty or failed flame sensor; Gas valve fault	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Check the condensate drain/trap is clear
109	Ignition failed – lockout because the boiler could not establish flame within the allowed ignition attempts pro repair	Gas supply off or low gas pressure; Air in the gas line after service; Dirty or failed igniter / flame sensor	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press Reset once
110	Ignition failure occurred (Hold) – an ignition attempt failed; the control holds before retrying pro repair	Temporary gas-supply or ignition issue; Dirty igniter or flame sensor	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work
111	Flame current lower than weak threshold (Hold) – the sensed flame signal is weak pro repair	Dirty or corroded flame sensor; Poor flame-sensor positioning; Marginal gas/air mixture	No homeowner action – a technician should inspect/clean the flame sensor
128	Fan speed failed during prepurge (Hold or Lockout) – the fan did not reach the required speed during prepurge pro repair	Vent or intake blockage; Blower wiring fault; Failing blower motor	Check the outdoor vent/intake terminals are clear of debris or ice; If it is a lockout, press Reset once
130	Fan speed failed during ignition (Hold or Lockout) – the fan did not hold the required speed during ignition pro repair	Vent or intake restriction; Blower wiring or blower fault	Check the outdoor vent/intake terminals are clear; If it is a lockout, press Reset once
132	Fan speed failed during run (Hold) – the fan did not maintain the required speed while running pro repair	Vent or intake restriction; Blower wiring or blower fault	Check the outdoor vent/intake terminals are clear
137	ILK (Interlock) failed to close (Hold) – an interlock switch did not close as expected pro repair	Interlock device tripped or not made; Interlock-chain wiring fault	No homeowner action – a technician must check the interlock chain
F1	Boiler control internal error. All fault conditions except F8 prevent operation pro repair	Internal boiler-control fault; Power disturbance	Power the boiler off, wait, then back on once; If it persists, a technician is required
F3	Gas valve status is on, with no call for heat pro repair	Gas valve or gas-valve circuit fault; Control board fault	No homeowner action – a technician should inspect the gas valve and control
F4	Supply sensor error pro repair	Supply temperature sensor wiring fault; Failed supply sensor	No homeowner action – a technician should check the supply sensor
F5	Tank sensor error (EBP only) pro repair	Tank (DHW storage) sensor wiring fault; Failed tank sensor	No homeowner action – a technician should check the tank sensor
F6	Return sensor error pro repair	Return temperature sensor wiring fault; Failed return sensor	No homeowner action – a technician should check the return sensor
F8	OAT (outdoor air temperature) sensor unreliable. The controller overrides outdoor reset and runs in setpoint mode instead; this fault does not stop operation pro repair	Outdoor sensor disconnected or out of range; Outdoor sensor wiring fault	No homeowner action needed for heat – the boiler keeps running on a fixed setpoint until a technician checks the outdoor sensor
LO	Lockout condition – the boiler control is locked out and will not operate until reset (commonly follows repeated ignition or flame failure). The ignition control's 3-flash LED code indicates an ignition control lockout pro repair	Repeated ignition failure; Dirty or failed flame sensor; Dirty burners or igniter problem	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press the reset button once to attempt to clear the lockout
ICE	Low temperature (freeze) protection is active – the control is running the boiler/pump to protect against freezing. This is an informational status, not a fault DIY-checkable	Low water/ambient temperature triggering freeze protection	No action needed – the boiler is protecting itself from freezing and resumes normal control automatically
2 flashes	Ignition control LED flash code: erroneous flame signal (flame sensed when none should be present, or a flame-sensing circuit problem) pro repair	Flame-sensing circuit fault; Gas valve leaking through; Moisture/contamination on the flame sensor	No homeowner action – a technician should inspect the flame-sensing circuit
3 flashes	Ignition control LED flash code: ignition control lockout (typically after repeated failed ignition attempts) pro repair	Repeated ignition failure; Dirty or failed igniter / flame sensor; Gas-supply or gas-pressure problem	Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work; Press the reset button once

Laars boiler codes we get called for most

11 — Ignition has failed 10 (ten) times – hard lockout. The boiler tried and failed to establish flame the maximum number of times

Typical causes include gas supply off or low gas pressure (3.5-14 in. wc); air in the gas line after service; dirty or failed igniter / ignition transformer. A few things are safe to check yourself (Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes 11 on Laars boilers throughout Greater Vancouver.

E011 — Flame loss lockout – the controller detected three consecutive flame losses while the unit was trying to run

Typical causes include flame sensor dirty or failed; gas valve wiring problem; gas supply problem / low gas pressure. A few things are safe to check yourself (Confirm the gas shutoff valve to the boiler is open; Confirm other gas appliances in the home work), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes E011 on Laars boilers throughout Greater Vancouver.

E005 — Water pressure switch error – lockout due to a problem with the water pressure switch (switch will not close unless at least 5 psi of water pressure is present)

Typical causes include low system water pressure (below ~5 psi); water pressure switch wiring fault; failed pressure switch. A few things are safe to check yourself (Check the system pressure gauge – if low, the system may need refilling by a technician; Press the Reset button once after pressure is restored), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes E005 on Laars boilers throughout Greater Vancouver.

16 — Operating temperature sensor detects water temperature greater than 203 degrees F (95 degrees C) – hard lockout (overheat)

Typical causes include circulator/pump not running or air-bound system; low system water pressure / inadequate flow; blockage at the central-heating (ch) inlet. A few things are safe to check yourself (Check the system pressure gauge is in the normal range (typically about 12-25 psi cold); Confirm heating-system valves are open), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes 16 on Laars boilers throughout Greater Vancouver.

Is it safe to keep running a Laars boiler with a fault code?

Most Laars fault codes put the boiler into a safe lockout for a reason. You can safely check the basics — gas supply on, power on, the thermostat calling for heat, system pressure in the normal range, and the condensate drain not frozen or blocked (a common cause in Vancouver cold snaps) — and restart it once. If the code returns, stop and book a technician. If you ever smell gas, leave the building and call your gas utility’s emergency line or 911 first. If a carbon-monoxide alarm sounds, get everyone out and call 911.

Laars boiler repair across Greater Vancouver

HeatLand has kept Metro Vancouver homes comfortable since 1999. Our licensed, insured technicians diagnose and repair Laars boilers — ignition faults, flame and sensor errors, low-pressure and pump problems, fan and flue faults, and control-board issues — including units we didn’t install. We’re brand-agnostic, carry common parts, and give you an honest repair-or-replace assessment with upfront pricing and a free estimate. If your boiler is beyond economical repair, we’ll show you right-sized, high-efficiency replacement options and the rebates available.

Need it sorted fast? We offer priority emergency boiler repair. Explore Boiler services, browse all boiler error codes by brand, or request a free estimate.

Laars boiler service areas

We repair Laars boilers across Greater Vancouver and the Fraser Valley, including:

Laars boiler error code FAQs

Can I reset my Laars boiler myself?

Yes — power-cycling the reset button once is generally safe after you’ve checked the basics (gas supply on, power on, the thermostat calling for heat, system pressure in the normal range, and the condensate drain not frozen or blocked (a common cause in Vancouver cold snaps)). If the boiler faults again right away, stop and note the code — repeatedly resetting a boiler that keeps locking out can mask a real problem. Call a licensed, TSBC-certified gas technician to diagnose it.

What does the Laars 11 code mean?

On Laars boilers, 11 commonly indicates ignition has failed 10 (ten) times – hard lockout. the boiler tried and failed to establish flame the maximum number of times. Confirm the exact meaning against your unit’s manual — codes can vary by model and series — and have the repair done by a licensed, TSBC-certified gas technician. HeatLand fixes this across Greater Vancouver.

Do you repair Laars boilers you didn’t install?

Yes. HeatLand is brand-agnostic and services Laars boilers throughout Metro Vancouver and the Fraser Valley, whether or not we installed the unit. We carry common parts and give you an honest repair-or-replace assessment.

Is a Laars boiler fault code an emergency?

No heat in cold weather is worth treating urgently. If you ever smell gas, leave the building and call your gas utility’s emergency line or 911 first. If a carbon-monoxide alarm sounds, get everyone out and call 911. For priority boiler repair across Greater Vancouver, call (604) 330-3812.

How much does Laars boiler repair cost in Vancouver?

It depends on the fault. Many Laars codes point to sensors, ignition or pump parts — usually far cheaper than replacement. We give upfront pricing and a free estimate before any work.

More Boiler error-code guides

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