pendulum action selector is stuck and i can't move it from setting 3, feels completely jammed.

Diagnosis

The pendulum action selector on the Bosch GST18V-60CN is a mechanical lever that controls the offset of the blade's stroke. When the lever feels completely jammed—specifically at setting 3 (the fastest, most aggressive cut)—it is almost always due to "sawdust compaction." Fine particulate matter from MDF or pressure-treated lumber mixes with the factory grease on the internal pivot pin, creating a hardened, cement-like paste that locks the lever in place. Because the selector lever is exposed to the cutting zone, dust enters the gap between the lever and the tool housing. Over time, this debris migrates into the spring-loaded detent mechanism. You can confirm this is the issue if you notice a visible ring of grey or brown dust accumulated around the base of the lever or if the lever feels "springy" but refuses to click into the next notch. If the lever doesn't move even with significant pressure, the debris has likely bridged the gap between the selector arm and the internal pendulum fork.

How to Fix It

Follow these steps to clear the jam without damaging the internal plastic detent.

1. Remove the 18V battery pack immediately to prevent accidental trigger activation while your hands are near the blade.
2. Use a high-pressure air compressor or a can of compressed air. Aim the nozzle directly into the gap between the pendulum lever and the tool body. Blast air in short, sharp bursts while simultaneously attempting to wiggle the lever.
3. If air fails, use a thin metal probe or a dental pick to gently scrape away the packed debris from the perimeter of the selector lever. Be careful not to pry the lever upward, as you may bend the internal spring.
4. Apply a specialized dry lubricant, such as a graphite-based spray or a PTFE (Teflon) dry lube. Avoid WD-40 or wet oils, as these attract more sawdust and will create a thicker sludge over time. Spray the lubricant directly into the pivot point and the detent notches.
5. Wait 60 seconds for the lubricant to penetrate. Then, using a pair of pliers (carefully padded with a cloth to avoid scratching the plastic), apply firm but steady pressure to move the lever from setting 3 to 2.
6. Once the lever breaks free, cycle it through all settings (0, 1, 2, 3) ten times rapidly to ensure the lubricant has coated the entire travel path and the detent clicks are crisp.

If That Didn't Work

• Deep Clean via Housing Removal: If the jam persists, the debris is likely inside the gear housing. Remove the outer casing screws (Torx T20) to access the pendulum fork. Use a vacuum to remove all loose chips and then manually clean the pendulum arm with a microfiber cloth and isopropyl alcohol before re-greasing with a lithium-based lubricant.
• Spring Replacement: If the lever moves but doesn't "lock" into place, the internal detent spring may have snapped or lost tension. This requires replacing the selector spring assembly. If the spring is fatigued, the lever will drift during operation, leading to inconsistent cut quality.
• Pivot Pin Inspection: Check for a bent pivot pin. If the tool was dropped or the lever was forced while the tool was jammed in a workpiece, the pin may be skewed. This requires a precision alignment or replacement of the selector arm assembly.
• Chemical Degreasing: Use a non-corrosive electronic contact cleaner to flush out the mechanism. This will dissolve the old, contaminated grease and allow you to start fresh with a dry lubricant.

Heads Up

• Avoid Wet Lubricants: Never use heavy machine oil or WD-40 on the pendulum selector; the "wet" residue acts as a magnet for sawdust, which will cause the lever to jam again within a few hours of use.
• Post-Cut Cleaning: After every project, use a blow-gun or vacuum to clear the area around the pendulum lever and the blade clamp to prevent debris buildup.
• Setting Awareness: Remember that setting 0 is for clean, fine cuts (no pendulum), while setting 3 is for rapid demolition. Switching settings while the motor is running can put undue stress on the pendulum fork.
• Blade Compatibility: Ensure you are using "T-shank" blades designed for orbital action. Using a non-orbital blade on setting 3 can cause excessive vibration and may contribute to mechanical wear on the selector mechanism.