my ryobi saw just stopped running mid-cut, now it doesn't do anything when i pull the trigger

Diagnosis

The Ryobi ONE+ 18V Reciprocating Saw (P519) is prone to sudden shutdowns during heavy-duty cutting, most commonly caused by the internal thermal overload protector. This safety mechanism is designed to trip when the motor windings reach a critical temperature, which happens frequently when cutting thick hardwoods or metal with a dull blade. When the protector trips, it physically breaks the electrical circuit to prevent the motor from melting, leaving the tool completely unresponsive to the trigger. Alternatively, this "dead" state can be caused by a failure in the trigger switch assembly or a loose battery terminal connection. Because the P519 uses a high-amp draw motor, the contact points inside the trigger can occasionally arc or pit, leading to a total loss of continuity. If the tool stopped instantly without a gradual loss of power or a "burning" smell, it is more likely a battery contact issue or a tripped thermal fuse. You can confirm a thermal trip if the tool suddenly regains power after a 30-minute rest period without any other interventions.

How to Fix It

Follow these precise steps to reset the tool and diagnose the power failure:

1. Isolate the Power Source: Remove the 18V ONE+ battery pack immediately. Inspect the gold-plated terminals on both the battery and the tool housing. Look for any charred plastic or bent tabs. Use a cotton swab with 90% isopropyl alcohol to clean the contacts to ensure a low-resistance connection.
2. Execute a Thermal Reset: Place the tool in a shaded, cool area. Do not attempt to "speed up" the cooling process with compressed air or refrigeration, as this can cause condensation inside the motor housing. Wait exactly 30 minutes to allow the internal bi-metallic strip in the thermal protector to cool and snap back into the "closed" position.
3. Cross-Verify the Battery: Insert the battery into a different Ryobi ONE+ tool (like a drill or blower). If the other tool doesn't run, the battery's internal PCB has tripped its own protection circuit. If the other tool works, the issue is isolated to the P519 saw.
4. Test the Trigger Action: With the battery removed, pull and release the trigger rapidly 10-15 times. This can sometimes clear debris or "set" the switch if it has become stuck in a partial position.
5. Re-engage and Test: Slide the battery back into the rail until you hear a distinct metallic click. Pull the trigger firmly. If the tool starts, the thermal overload was the culprit.

If That Didn't Work

• Inspect the Blade Shoe Tension: Check if the blade is jammed or if the shoe is pinched tightly against the material. If the motor is stalled mechanically, the tool may refuse to start to protect the gears. Loosen the blade clamp and try to trigger the tool without a blade installed to see if it spins freely.
• Check for Internal Wire Fatigue: If you are comfortable opening the casing, remove the housing screws and inspect the wiring leading from the battery terminals to the trigger switch. The P519 can develop "wire rub" where the vibration of the reciprocating action chafes the insulation, causing a short circuit that blows the internal fuse.
• Replace the Trigger Switch: If the battery is confirmed working and the tool is cool, the trigger switch assembly has likely failed. This is a common failure point in the P519. You will need to replace the switch assembly; ensure the replacement part matches the specific 18V ONE+ voltage rating to avoid frying the motor.
• Verify Battery Voltage: If using an older NiCd battery instead of a Lithium-ion pack, the voltage may have dropped below the operational threshold mid-cut. Charge the battery fully for 4-6 hours and try again.

Heads Up

• Blade Selection: Always use a high-TPI (teeth per inch) blade for metal and a low-TPI blade for wood. Using a wood blade on metal causes massive friction, which trips the thermal overload almost instantly.
• Avoid "Force-Feeding": Do not push the saw aggressively into the material. Let the tool reach full RPM and allow the blade to do the work; forcing the cut increases amperage draw and heat.
• Battery Heat: If the battery feels hot to the touch, stop immediately. High-discharge batteries can overheat independently of the tool, triggering a safety shutdown within the battery pack itself.
• Debris Clearing: Periodically blow out the motor vents with compressed air. Sawdust buildup inside the housing acts as an insulator, trapping heat and making the thermal protector trip much more frequently.