Four common problems can cause a pellet stove to stop working. We'll take a look at each situation below.
Before starting any troubleshooting procedure, set your stove on “manual” operation.
1. Stove Starts but Quickly Stops
If your pellet stove is running for 15 minutes, then shutting off leaving burn grate full of pellets, check for a defective igniter (Figure 1).
Step 1.1 - Unplug the stove and remove the access panels to the components.
Step 1.2 - Remove the igniter (Figure 2) and unplug it at the connector.
Step 1.3 - Check the igniter with a continuity test across the igniter’s connectors while moving the wires around for a possible intermittent break.
Step 1.4 - If the test shows that it’s open, replace the igniter.
Step 1.5 - A good igniter should measures between 30 and 60Ω. Check the wires up to their origin and power it up to take a voltage reading. If there is no voltage present, unplug and look for a burnt fuse leading to or on the PC board.
Step 1.6 - If there is no fuse or the fuse is good, the cause is likely to be with the control board.
2. Empty Burn Grate
If your stove starts and then stops shortly thereafter, leaving nothing in the grate, the problem could come from an empty pellet hopper, an insufficient or leaky vacuum throughout the unit, or a faulty high limit switch not closing (Figure 3).
Step 2.1 - Check the hopper for fuel; if empty, add pellets to it and a small handful to the burn grate and try it again.
Step 2.2 - If the problem persists without any more pellets falling into the burn grate, make sure that the door and the ash pan are closed tightly.
Step 2.3 - Check that your venting (Figure 4) and air intake are clear of any obstruction or creosote. Fly ash collecting from incomplete combustion during startups, shutdowns, or incorrect operation of the stove can cause accumulations. Clean if necessary.
Step 2.4 - While the combustion fan is running, hold a newspaper up to the vent to confirm a strong and steady flow of air coming out. If not, proceed to step 12.
Important Safety Note—For the following steps, unless instructed otherwise, unplug the stove before handling any electrical wires and components, follow the instructions then power the stove back on to re-test. If the test was conclusive, replace that specific component. Before proceeding to the next step, replace everything as it was originally then repeat for the next step.
Step 2.5 - Unplug the unit and remove the panels to expose the internal components. The auger might be fused—check for a blown fuse and replace it if necessary. Retry.
Step 2.6 - If the hopper lid is equipped with a safety switch (Figure 5), test the switch by unplugging both leads and connecting them together using a makeshift jumper wire with matching male blade connectors at both ends (Figure 6). Retry.
Step 2.7 - With the unit plugged in, carefully take a voltage reading across the auger motor terminals (Figure 7) using a multimeter on AC volts setting. If you get a 120V reading and the auger doesn’t turn, it needs to be replaced.
Step 2.8 - If you didn’t get the voltage across the auger terminals, locate the high-limit switch (as in Figure 3), and unplug both wires from its terminals, then connect the two wires together using your jumper wire (Figure 6). Retry.
Step 2.9 - Locate the vacuum switch (Figure 8), pull out the two wires from their terminals, and repeat the same test with the jumper wire. Re-test. If the auger still doesn’t work, pull out the vacuum tube from its fitting on the stove and wipe the end of it clean.
Step 2.10 - With the unit powered on, suck the air lightly from the tube to activate the switch. If the auger still doesn’t start turning, the vacuum switch is faulty, and a 120V voltage measurement between one of its terminals to ground will confirm this diagnosis.
Step 2.11 - If there is no voltage reading, the control board needs to be replaced.
Step 2.12 - If the auger starts while activating the vacuum switch(step 11), remove the venting pipe and with a flashlight, take a look at the combustion fan for debris. If it is clear, the combustion fan is defective and needs to be replaced.
3. Random Shut Downs
Step 3.1 - Take a look inside the burn chamber—there is likely more unburned pellets than usual laying around the burn chamber. This is an indication of excessive combustion air resulting in some pellets blown out of the grate from an excessive draft and the rest burning faster than they come in.
Step 3.2 - Clean the glass for a better view of the flame, add some pellets to the burn grate for faster lighting and close the door. Re-start the stove.
Step 3.3 - Once the unit has resumed its normal fan speed and operation (5 or more minutes), verify the flame quality: it will likely be white to yellow, creating smoldering pellets and pellets flying up into the air (popcorning).
Step 3.4 - You should start readjusting by running the feed on high for about 10 minutes.
Step 3.5 - You can then close the damper completely and evaluate the flame. A smoky red/orange flame with evidence of soot at the top of the flame indicates a lack of air.
Step 3.5 - Gradually open up the damper as needed to obtain a yellow flame brisk enough to carry ash out of the grate without carrying pellets out as well—popcorning.
4. Pellet Overflow
Pellet stoves can stop working unexpectedly if their burn grates are running over with pellets.
Step 4.1 - At first sight, you will notice an excessive buildup of soot on the glass.
Step 4.2 - Looking inside you’ll see that the grate is over-flowing with an accumulation of pellets. With the pellets removed, you’ll also notice an excessive amount of ashes inside the burn grate. This is an indication that the incoming amount of combustion air is not enough to consume the amount of pellets going in.
Step 4.3 - Remove the burn grate and clean it out before returning it to the burn pot.
Step 4.4 - After adding a few pellets in the grate (to prime it) restart the stove.
Step 4.5 - Return to steps 3.3 and follow each step through to 3.5 to readjust the unit for proper burning.
Step 4.6 - If this problem was a frequent occurrence and you can’t get the right flame setup inside the burn grate, you probably didn’t install an air inlet pipe from the outside of the house, and the internal supply inside the house isn’t enough for proper combustion. You can seek a professional opinion, but you will likely have to had the air inlet pipe installation.
Step 4.7 - As a last possible cause, with all the dust, ash, and soot, the combustion fan’s bearing could have deteriorated to the point of “dragging”, slowing down and decreasing the air flow out of the flue pipe. This is even more obvious if the fan ha become noisy or squeaky. You can easily test your fan on your work bench after removing it from the stove. Replacing the fan is simple enough, but make sure the gasket is also a new one went re-installing the new fan.