the tool randomly shuts off for a second then comes back on, especially when i'm putting pressure on it.

Diagnosis

The intermittent power cycling on the DeWalt DCS354B is typically caused by "contact bounce" within the battery rail system. Because this is an oscillating tool, it generates high-frequency vibrations (up to 20,000 OPM) that can cause a slightly loose battery to micro-shift within the housing. When you apply downward pressure during a cut, you are subtly altering the angle of the tool, which can pull the battery terminals just a fraction of a millimeter away from the internal contact plates, breaking the electrical circuit for a millisecond. This is often exacerbated by the accumulation of fine sawdust or metallic debris inside the battery slot, which acts as a shim, preventing the battery from seating fully. To confirm this is the issue, grip the battery firmly with your hand and apply pressure toward the tool's motor housing while running the tool; if the cutting out stops while you are manually holding the battery in place, the fault is definitely a mechanical connection failure between the pack and the tool.

How to Fix It

To resolve the connection instability and restore a solid electrical path, follow these precise steps:

1. Remove the battery pack and use a can of compressed air to blow out the battery terminal cavity. Focus on the deep recesses where the brass pins are located to remove any trapped sawdust or gypsum dust.
2. Dampen a cotton swab with 91% or higher Isopropyl Alcohol. Scrub the three flat brass contact plates inside the tool's battery port. You will likely see a dark layer of carbon buildup or oxidation; continue scrubbing until the brass appears bright and reflective.
3. Clean the corresponding terminals on the battery pack using the same method. Ensure there is no sticky residue or oil on the contacts, as this creates a high-resistance layer that can trigger the tool's internal protection circuit to trip.
4. Inspect the battery release buttons on both sides of the tool. Press them and ensure they snap back instantly. If a button is sticking, the battery may not be locking into the "final click" position, leaving a gap that allows the battery to vibrate loose.
5. Insert the battery and give it a firm push until you hear a distinct double-click. Give the battery a physical shake; if there is any lateral movement, the locking lugs are worn or contaminated.

If That Didn't Work

• Test the tool with a different 20V Max battery, preferably a higher-capacity 5.0Ah or 6.0Ah pack. Larger batteries have slightly different weight distributions and terminal tolerances; if a larger pack solves the problem, the issue is likely worn-out locking tabs on your original battery pack rather than the tool itself.
• Check for a loose trigger switch assembly. If the tool is cutting out specifically when you squeeze the trigger harder or tilt the tool, the internal wiring to the switch may have frayed or loosened due to the constant oscillation. This requires opening the housing to reseat the wire connectors.
• Inspect the brush assembly if you are using an older model of the DCS354B. While most are brushless, any carbon brush wear can cause intermittent sparking and power loss under load, which mimics a battery connection issue.
• Verify that the accessory blade is tightened fully. A loose blade can cause an unbalanced vibration that is violent enough to shake the battery out of contact. Use the provided hex key to ensure the blade is clamped tight against the washer.

Heads Up

• Avoid using "universal" or third-party aftermarket batteries with this tool. These often have slightly off-spec terminal dimensions that lead to the exact intermittent power loss described here.
• Never use conductive lubricants or WD-40 on the battery terminals, as this attracts dust and creates an insulating paste that will worsen the connection.
• Be cautious when the tool cuts out mid-cut; the sudden loss of power combined with the oscillation can cause the tool to "jump" or kick, potentially leading to a laceration.
• Periodically check the battery rails for plastic wear. If the plastic guide rails are shaved down, the battery will wobble, and you may need to apply a small piece of electrical tape to the rail to tighten the fit.