Quick Answer
Common causes include the sliding flame broiler left partly open, ash and grease loading the firepot and grease tray, damp or low-grade pellets, a dirty or misplaced temperature probe, a worn lid gasket, wind exposure, and comparing a grate thermometer with the controller's own probe located elsewhere in the barrel. Check first that the flame broiler is fully closed for indirect cooking and that the firepot is clean.
Which symptom matches yours?
- Temperature overshoots the setpoint by 75°F or more, then falls well below it
- Wild swings only at low smoke settings
- Grate-level readings disagree sharply with the controller display
- Heavy smoke, then a flare, then a drop
- Cycling worsened after a long, greasy cook
- Swings appear only on windy or cold days
Diagnostic decision tree
Swings with direct flame visible under the grates
→The sliding flame broiler is open — close it fully for indirect cooking.
Overshoot then stall
→Firepot ash and grease buildup disrupting combustion.
Controller and grate thermometer disagree
→Probe placement and calibration, not a control fault.
Worst at 180–225°F
→Low-smoke settings amplify cycling; pellet quality and airflow matter most here.
Smoke escaping around the lid
→Lid gasket or barrel fit — seal it before chasing the controller.
Only in wind or cold
→Heat loss from a single-wall barrel; shelter the grill and expect longer recovery.
Fixes, easiest first
1. Close the sliding flame broiler
AddressesDirect flame reaching the cooking chamber and spiking the reading.
- Locate the flame broiler slide plate handle at the side of the barrel.
- For any indirect or low-and-slow cook, push it fully closed so the firepot is covered.
- Confirm the plate actually slid — grease and ash can hold it part-open even when the handle moves.
- Reserve the open position for deliberate direct-flame searing at high setpoints.
Expected resultSteadier temperatures and no visible direct flame under the grates during indirect cooks.
When to stopIf closing the broiler restores stability, nothing further is required.
2. Clean the firepot, grease tray and barrel
AddressesCombustion disruption from ash and grease — the most common physical cause of swings.
- Unplug the cold grill and remove grates, grease tray and the flame broiler plate.
- Vacuum the firepot to bare metal and clear the air holes.
- Scrape the grease tray and clear the grease drain tube, which clogs on 850-class cookers with long, fatty cooks.
- Vacuum ash from the barrel base and reinstall components in the correct order.
Expected resultCleaner combustion, less flare-driven overshoot and a shorter recovery after lid openings.
When to stopIf stability returns, adopt this cleaning every few cooks rather than every season.
Vacuum only cold ash, and never use water on a hot grease tray.
3. Verify what the controller is actually measuring
AddressesApparent swings caused by probe placement and grime.
- Wipe the internal temperature probe — a grease-coated probe reads slow and lagging, which makes the controller overcorrect.
- Place a known-good leave-in thermometer at grate level in the centre of the cooking surface.
- Compare readings across a full 30-minute steady period rather than a single moment.
- Expect a genuine offset between the barrel-mounted probe and grate level; cook to the grate reading.
Expected resultA consistent, explainable offset instead of erratic disagreement.
When to stopIf the internal probe reads wildly or intermittently, replace it.
4. Fix pellet quality and hopper condition
AddressesInconsistent fuel, which the controller cannot compensate for.
- Empty the hopper and vacuum fines from the base.
- Refill with fresh, dry, low-ash hardwood pellets from a sealed bag.
- Do not leave pellets in the hopper between cooks in damp weather.
Expected resultMore even feeding and smaller cycling amplitude.
When to stopIf fresh pellets stabilise the cook, the previous batch had taken on moisture.
5. Seal the cook chamber and manage conditions
AddressesHeat and smoke loss that forces the controller to over-fire.
- Run the dollar-bill test around the lid: if the note pulls out freely at a spot, that section is leaking.
- Fit a high-temperature gasket to the lid lip if leakage is significant.
- Confirm the chimney is clear and set consistently rather than being adjusted mid-cook.
- Shelter the grill from direct wind and allow longer recovery after opening the lid in cold weather.
Expected resultSmaller swings and faster recovery to setpoint.
When to stopPersistent large swings with a sealed, clean grill and fresh pellets point to the controller or probe.
Pit Boss 850 / Navigator 850: what makes this model different
- Cooking area
- Roughly 850 sq in across main and upper racks in the 850-class Pit Boss pellet grills
- Distinctive feature
- Sliding flame broiler that exposes direct flame from the firepot for searing — a common source of swings when left open
- Controller
- Digital control board with a barrel-mounted temperature probe and meat probe inputs; PID-style control on current Navigator and Pro Series boards
- Construction
- Single-wall steel barrel; cold and wind measurably affect stability
- Maintenance pressure points
- Firepot ash, grease tray, grease drain tube and hopper fines
When to stop troubleshooting
- Flames or heavy smoke coming from the hopper — shut the grill down immediately and do not restart it.
- A grease fire in the barrel: shut the grill off, keep the lid closed, and never use water.
- Burning-electronics smell, a hot control housing, or a scorched power cord.
- The controller display behaves erratically or resets during cooks — that is a control board issue, not a tuning problem.
- Clean grill, fresh pellets, sealed lid and closed flame broiler but swings above roughly 100°F persist — contact Pit Boss support.
Sources and references
- Pit Boss Grills support — pellet grill troubleshooting — Dansons Inc. (Pit Boss Grills)
- Pit Boss owner's manuals (Pro Series and Navigator) — Dansons Inc. (Pit Boss Grills)
Procedures are summarised from the sources above and from the owner's manual for this model. Always follow the manual supplied with your grill where it differs.