dewalt drill smells like burning and gets really hot near the motor just holding the trigger for a few seconds

Diagnosis

The burning smell and rapid heat buildup in the DCD771C2 are classic symptoms of a catastrophic failure in the motor's electrical or mechanical integrity. Because this model utilizes a brushed DC motor, the most common culprit is "arcing" at the commutator. When the carbon brushes wear down unevenly or the commutator develops "pitting" (small burnt craters), the electrical current jumps across gaps, creating intense heat and a distinct ozone/burnt plastic smell. If the heat is felt almost instantly upon pulling the trigger without a load, you likely have a partial short in the armature windings, meaning the insulation on the copper wire has melted, allowing current to bypass the coils and generate raw heat. Alternatively, the issue may be mechanical friction caused by a seized or contaminated motor bearing. If the front bearing has failed or ingested metallic debris from the gear housing, the motor must fight immense physical resistance to spin. This forces the motor to draw maximum amperage from the 20V battery, which rapidly overheats the windings and the trigger switch assembly. You can confirm this by removing the battery and attempting to spin the chuck by hand; if there is any "grittiness" or significant resistance compared to a healthy unit, the bearing or the planetary gears are the primary failure point.

How to Fix It

To resolve this, you must replace the motor assembly and inspect the trigger switch for heat damage.

1. Safety First: Remove the 20V Max battery pack immediately. Do not attempt to disassemble the tool with the power source connected.
2. Case Disassembly: Using a T15 Torx driver, remove the screws from the clamshell housing. Be careful not to lose the small screws located near the grip and the base of the handle. Gently pry the two halves of the casing apart using a plastic trim tool to avoid marring the plastic.
3. Component Extraction: Locate the motor assembly at the rear of the tool. Carefully disconnect the two heavy-gauge wires connecting the motor to the trigger switch. Note the polarity (color coding) to ensure the drill does not spin in reverse upon reassembly.
4. Motor Replacement: Unscrew the motor mounting bolts. Slide the old motor out of the housing. Install a replacement DCD771-compatible brushed motor. Ensure the motor shaft is seated fully and flush against the planetary gear assembly.
5. Cleaning and Lubrication: Before closing the case, use compressed air to blow out any carbon dust or metallic shavings from the gear housing. Apply a small amount of high-temp lithium grease to the planetary gears if the grease appears dry or blackened.
6. Reassembly: Reconnect the motor wires to the trigger switch, ensuring the connections are tight and insulated. Snap the housing back together and tighten the T15 screws.
7. Testing: Insert the battery and pull the trigger in short bursts. Check for smooth acceleration and a lack of burning odors.

If That Didn't Work

• Replace the Trigger Switch: If the motor is new but the heat persists or the smell remains, the trigger switch (potentiometer) may have an internal short. A failing switch can send erratic voltage to the motor or overheat itself, melting the surrounding plastic housing. Replace the trigger assembly entirely.
• Inspect the Planetary Gearbox: If the motor is straining, a chipped tooth in the planetary gear set can cause a "binding" effect. This creates massive mechanical drag that manifests as heat in the motor. If you see metal flakes in the grease, the gearbox assembly must be replaced.
• Check for Battery Internal Short: A faulty 20V battery cell can occasionally cause a voltage spike or instability. Test the drill with a different, fully charged 20V Max battery. If the problem disappears, the original battery pack is the source of the electrical instability.
• Verify Chuck Alignment: If the chuck is jammed or the internal bearings of the spindle have collapsed, it will put an immense load on the motor. Try removing the chuck (if applicable) or spinning the spindle to ensure it moves freely without the motor engaged.

Heads Up

• Carbon Dust Danger: Always blow out the motor area with compressed air during service. Accumulated carbon dust from the brushes can become conductive, leading to "tracking" shorts that can fry a brand new motor.
• Avoid "Stalling": To prevent this from happening again, avoid "stalling" the drill (holding the trigger while the bit is completely stopped in a hard material). This creates a "locked rotor" condition that generates maximum heat in seconds.
• Cool-Down Periods: If you are drilling large diameter holes in hardwood, allow the tool to idle (spin without a load) for 10 seconds between holes to use the internal fan to cool the armature.
• Grease Quality: Never use WD-40 or thin oils inside the gear housing; use only high-pressure lithium grease. Thin oils will sling off the gears and may migrate into the motor windings, causing a fire hazard.