Diagnosis
The temperature swings on the Pit Boss Pro Series 1150 are typically caused by "carbon crusting" on the RTD (Resistance Temperature Detector) probe. The probe is a thermistor that measures electrical resistance to determine heat; when a layer of carbonized grease and ash builds up on the metal rod, it creates an insulating barrier. This causes the probe to lag, reporting a lower temperature than the actual air in the barrel. The controller then continues to feed pellets and crank the induction fan, leading to a massive overshoot—often 100°F or more—before the probe finally registers the heat and shuts down the auger. Additionally, this issue can be exacerbated by ash accumulation in the fire pot or a partial blockage in the airflow paths. If the ash buildup is significant, the pellets don't burn evenly, creating "hot spots" that confuse the sensor. You can confirm this is a probe issue if you notice the grill temperature climbing steadily past your set point without the auger stopping, or if the temperature fluctuates wildly (e.g., jumping from 225°F to 325°F in a matter of minutes) despite no changes to the settings.
How to Fix It
To resolve temperature instability, you must restore the thermal conductivity of the RTD probe and clear the combustion chamber. Follow these steps precisely:
- Completely power down the grill and unplug it from the wall outlet to ensure the auger does not accidentally engage during cleaning.
- Remove the cooking grates and the heat diffuser (the heavy metal plate above the fire pot).
- Locate the RTD probe. This is the small, silver metal rod protruding from the left side wall of the firebox.
- Using a fine-grit scouring pad, a piece of 400-grit sandpaper, or a small piece of fine steel wool, gently scrub the silver rod. Remove all blackened carbon deposits and grease until the metal is bright and shiny. Do not use heavy pressure, as bending the probe can damage the internal sensor.
- Using a shop vacuum with a narrow nozzle attachment, thoroughly vacuum out the fire pot. Ensure you remove all clumps of unburnt pellets and ash from the bottom of the pot and the surrounding area.
- Vacuum the area around the induction fan (located beneath the hopper) to ensure maximum airflow into the combustion chamber.
- Reinstall the heat diffuser and grates, then plug the unit back in and run a test cycle at 225°F to calibrate.
If That Didn't Work
- Check the RTD probe connection. Locate the wiring harness behind the control panel and ensure the probe plug is seated firmly and is not corroded. A loose connection creates electrical resistance that the controller interprets as a temperature change, causing the "swing" effect.
- Inspect the auger drive for "pellet bridging." If pellets are clumped in the hopper, the auger may be intermittently jamming and then releasing a large surge of pellets into the pot, causing sudden spikes in heat. Clear the hopper and ensure you are using high-quality, dry pellets.
- Verify the seal of the lid. If the gasket is worn or if the lid does not seat firmly against the barrel, cold air leaks can trick the probe into thinking the grill is colder than it is, causing the controller to overcompensate.
- Replace the RTD probe entirely. If the internal sensor has drifted due to heat fatigue, scrubbing will not fix it. Order a replacement Pro Series RTD sensor and swap it out, ensuring the new probe is positioned exactly where the factory original was located.
Heads Up
- Clean the RTD probe every 3 to 5 cooks. Carbon buildup is inevitable, and regular maintenance prevents the "overshoot" phenomenon.
- Always vacuum the fire pot after every single use. Ash buildup restricts oxygen flow and is the primary cause of erratic temperature behavior.
- Avoid using "cheap" pellets with high sawdust content, as these produce significantly more ash and clumping, which clogs the fire pot faster.
- Never use a wire brush on the RTD probe; use only fine abrasives to avoid scratching the sensor housing.