Harman Pellet Stove Feed Fault Vs Igniter Fault Tree
Why this matters
A Harman pellet stove that will not establish a fire fails in one of two broad ways: pellets are not reaching the burn pot (a feed fault) or pellets are arriving but not lighting (an igniter or air fault). Techs swap parts in the wrong order, replacing a good igniter when the auger never delivered fuel, or rebuilding a feed system when a dirty igniter channel was the real fault. Harman's PF/P-series, Accentra, and Absolute lines use an Exhaust Sensor Probe (ESP) and feed-by-temperature control logic, so the stove's own behavior tells you which branch you are on if you read it correctly. Getting the branch right on the first visit is the difference between a one-trip fix and a callback.
The split also matters for safety: an igniter that energizes into a pot full of unburned pellets from a failed prior attempt can produce a delayed light-off and a small puff. Always clear the pot before retesting.
Unburned pellets accumulated from repeated failed ignition attempts can ignite all at once on the next try, producing a flash and pressurizing the firebox. Before any igniter or feed test, open the stove, empty the burn pot completely, and clear the igniter channel. Never test ignition on a pot loaded with cold fuel.
Symptom presentation
Establish the failure mode by watching one full start cycle with the door closed and the room sensor calling for heat:
- Pure feed fault: auger may hum or be silent, no pellets drop, igniter glows but has nothing to light, stove faults out cold. Pot stays empty.
- Pure igniter/air fault: pellets accumulate in the pot during start but never light, or light very late; you may smell off-gassing. Pot fills but stays dark.
- Mixed: a trickle of pellets and a weak smolder that dies, pointing to marginal feed plus marginal air or a fouled ESP.
Note the control-board status light or distribution-fan behavior; Harman boards stage the start, and the stage it stalls at narrows the branch.
Quick checks
- Confirm the hopper has fuel and the auger path is clear. Bridged or fines-clogged pellets stall the auger. Run the hopper down and check for a jam at the auger inlet.
- Verify the burn pot, igniter channel, and ESP probe are clean. A pot crusted with clinker, an ash-blocked igniter air hole, or a sooted ESP probe all sabotage ignition.
- Check the door and ash-pan seal. Harman ignition depends on the combustion blower pulling air through the igniter channel. A leaking door or ash-pan gasket steals that airflow and pellets smolder instead of lighting.
- Listen to the auger and combustion blower. A silent combustion blower means no draft and no light; do not confuse it with the room-air distribution fan.
- Read the ESP behavior. If the stove never advances out of start because the ESP never sees a temperature rise, that can be a no-fuel condition OR a failed probe, the tree below separates them.
Isolation tree
Burn pot stays empty through the whole start cycle (feed branch).
- Auger motor silent and no hum: check the auger motor circuit and the board feed output; a failed feed motor or open circuit. Confirm voltage at the motor during the feed call.
- Auger hums but does not turn: mechanical jam, a foreign object or a long fine-packed plug at the auger flight, or a seized bushing. Clear the jam and rotate the auger by hand.
- Auger turns but pellets do not advance: hopper bridge, oversized or swollen pellets, or a worn auger flight. Clear the bridge, check pellet quality.
- Feed motor and auger fine but board never commands feed: control-board feed-logic or a room-temperature sensor reading satisfied. Verify the room sensor / call-for-heat input.
Pot fills with pellets but they do not light (ignition/air branch).
- Igniter element does not glow (no orange in the channel): test igniter resistance per the Harman spec and confirm board output voltage to the igniter terminals. Open element or no board output means replace igniter or trace the circuit.
- Igniter glows but pellets do not catch: airflow fault. Combustion blower weak, igniter air hole blocked, door/ash-pan gasket leaking, or exhaust vent restricted. The igniter needs forced air through the channel to ignite; restore the draft path.
- Pellets light very late or smolder then die: marginal everything, low feed rate plus weak air plus an aging igniter. Clean fully, retest, and replace the igniter if it is slow to glow.
Stove faults on the ESP (status light / error pattern points to exhaust temp).
- ESP never rises and pot was confirmed getting fuel and a glow: probe fouled or failed. Clean the ESP; if it still does not register a rise during a real fire, replace it.
- ESP rises but stove still faults: combustion air or exhaust restriction tripping the logic, inspect the venting and combustion blower.
Confirming diagnosis
After the repair, clear the pot, set the stove to a manual or test start, and watch one full cycle:
- A correct feed delivers a steady measured drop of pellets into the pot during the start stage, not a flood and not a trickle.
- A correct igniter glows bright orange in the channel within the start window and pellets ignite at the channel side first.
- The ESP should show a rising exhaust temperature that lets the board transition out of start into run. If the stove reaches a stable flame and steps to its run mode, the branch you fixed was the cause.
Run a full thermostat-satisfied shutdown and a second start to confirm repeatability.
Remediation
- Feed faults: clear auger jams and hopper bridges, replace a failed or seized auger/feed motor, advise the customer on premium low-fines pellets and not letting the hopper run to dust.
- Igniter faults: replace an open or slow igniter with the OEM element, clear the igniter air hole every cleaning.
- Air faults: replace failed door and ash-pan gaskets, clean the combustion blower wheel, clear the exhaust vent and termination of ash.
- ESP faults: clean every service; replace a probe that no longer tracks a real fire.
- Always end with a full burn-pot and venting cleaning so the next light reads true; no-light callbacks are most often a maintenance debt, not a dead part.
References
- NFPA 211, Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances (pellet-vent requirements).
- UL 1482 / UL 127, listing standards covering pellet and solid-fuel room heaters.
- CSIA Certified Chimney Sweep technical guidance on pellet appliance service and venting.
- Harman / Hearth & Home Technologies, owner and service manuals for Accentra, Absolute, and PF/P-series stoves (ESP logic, igniter resistance spec, feed adjustment).