Inconsistent feeding: Generally, there are only two things that will affect the feed rate in the stove, a mechanical issue with the feed system or an electronic issue with the controller.
Mechanical issues are easier to diagnose so you should start there. There are 3 things to you should look for.
- Accumulation of fines (dust) at the base of the hopper - When you get a collection of fines down at the base of the hopper, at the opening where the auger flighting gather pellets, if there is too much debris, the stove will not be able to maintain a constant feed rate as the fines will be blocking the auger from getting pellets. When this happens, the stove will have problems starting on the first try and you may have a problem with the stove running on the lowest heat setting. Clean it out and verify that this is not an issue.
- Worn out auger bushing - Similar symptoms as above, dust will get between the auger shaft and the bushing and slow the rotation of the auger. If the bushing is worn out you'll notice a collection of dust in the mechanical cabinet directly under the auger motor. If you see this, replace the auger bushing. It is advisable whenever an auger bushing is replaced, also replace the auger motor
- Worn out auger motor - Auger motors do go bad. The coil can become less conductive over time. You can visibly see this by looking at the nylon sidewalls or cellophane covering the copper wire in the coil. If it appears yellowish-brown, the coil is bad and the motor should be replaced. With a worm out auger motor, often it turns just fine at a cold start-up but becomes slower with continued use.
Each of these symptoms will mechanically cause the feed motor to turn slower. All of these symptoms should be tested on a "clean" stove and vent, as a dirty stove or vent can also contribute to or exacerbate these symptoms.
Loss of Variable Speed Function to the Exhaust Blower:
Whitfield controllers for the Profile Series, Optima and T300 have three different voltage ranges for LOW, MEDIUM and HIGH. At startup, the default is MEDIUM. At the base of the controller, in the front, there is a door that drops down, you'll see some ports for testing voltages and a button for trim control. Make sure that your trim control is set for the middle by advancing the trim control button. Trimming the red control lights advances or retards the feed setting, advancing the yellow room fan lights advances or retards the combustion motor voltage. Make sure both of these are set for the middle. Does your stove run better? You may have them at opposing ends...low feed and high RPM = low or inconsistent flame. Likewise, having high feed and low RPM just builds a big mess in the burn pot.
If setting the trim controls back to neutral still has no effect, take some reading with a multimeter across the combustion and common testing ports. You should see a voltage change from LOW> MEDIUM and HIGH. If not, replace the controller.