my ryobi drill battery charges fine but the drill only works on high speed, low speed does nothing

Diagnosis

The issue with your Ryobi ONE+ P215K1 is almost certainly a mechanical failure within the two-speed planetary gear assembly, specifically involving the sliding selector collar. In this model, the speed switch doesn't control electricity, but rather physically shifts a collar to engage different gear ratios. When the drill works in "2" (high speed) but is dead in "1" (low speed), it means the selector collar is failing to fully seat into the low-gear position, or the internal splines of the low-speed gear have stripped or become obstructed. This typically happens due to "gear walking," where the switch isn't pushed completely into position, or because fine drywall dust and sawdust have migrated into the gear housing, creating a physical blockage that prevents the collar from sliding forward. To confirm this, listen closely to the drill while pulling the trigger in the "1" position; if you hear the motor spinning (a high-pitched whine) but the chuck isn't turning, the motor is working, but the mechanical link to the chuck is severed. If there is total silence, the switch may be jammed in a "neutral" dead zone between gears.

How to Fix It

To resolve this, you need to clear the mechanical obstruction and ensure the selector collar is properly aligned. Follow these steps:

1. Remove the 18V battery immediately to prevent accidental trigger pulls while your hands are near the gears.
2. Set the speed selector switch to the "2" position. While holding the switch firmly in "2," rapidly pull the trigger for 2 seconds. This ensures the high-speed gear is fully seated.
3. Slowly slide the switch to the "1" position. Do not just flick it; apply firm, steady pressure until you feel a distinct "click" or stop. If the switch feels "mushy," it is likely obstructed by debris.
4. Use a can of compressed air or a high-pressure air nozzle to blow directly into the gap around the speed selector switch. Aim the airflow toward the front of the drill to push any accumulated dust out of the housing.
5. If the switch is still not engaging, apply a small amount of dry PTFE lubricant or silicone spray to the external edges of the sliding switch. Avoid using WD-40, as the oil can attract more dust and create a sludge that jams the gears further.
6. Cycle the switch from 1 to 2 and back to 1 at least 15 times rapidly to clear any remaining grit from the sliding tracks.
7. Reinsert the battery and test the "1" setting at a low trigger pull first to avoid stripping the gears if they are only partially engaged.

If That Didn't Work

• Internal Gear Inspection: If the drill is out of warranty, remove the housing screws (typically T10 or T15 Torx) to expose the gearbox. Check for a broken spring on the selector collar. If the spring has snapped, the collar will not lock into the low-speed gear, causing the drill to slip or fail to engage.
• Check for Stripped Splines: Inspect the low-speed planetary gear for sheared teeth. If the metal teeth on the low-speed gear are stripped, the motor will spin, but no torque will reach the chuck. In this case, the entire gear assembly must be replaced.
• Collar Realignment: Sometimes the plastic housing of the P215K1 warps slightly, causing the switch to misalign. Gently loosen the housing screws by a quarter-turn, slide the switch to "1," and then retighten the screws. This can sometimes "center" the mechanism.
• Motor Brush Check: While rare for a speed-specific issue, check if the motor is overheating. If the drill was used heavily on high speed, the thermal protector may be limiting power, making the low-torque gear feel like it isn't working. Let the tool cool for 30 minutes and try again.

Heads Up

• Never shift the speed selector switch while the trigger is pulled. Shifting under load can shear the internal plastic and metal teeth, permanently ruining the gearbox.
• Always ensure the switch is clicked fully into position before starting a hole. A "half-engaged" gear will strip rapidly under the pressure of a screw or drill bit.
• Keep the vents of the P215K1 clear of debris. Dust buildup doesn't just affect the motor; it migrates into the gear housing and causes the exact switching failure you are experiencing.
• If you notice a grinding sound when switching to low speed, stop immediately. This indicates a misalignment that will lead to total gear failure if forced.