my dewalt dcd771 drill won't charge at all, the charger light doesn't even come on

Diagnosis

When a DeWalt DCD771C2 charger fails to show any LED activity (no red, green, or blinking light), you are dealing with a total circuit failure. This is typically caused by one of three things: a tripped internal thermal fuse, a failure in the AC input stage of the charger, or a complete break in the power cord continuity. Because the DCD771C2 uses a basic 20V Max charger, there is no complex "handshake" between the battery and charger that would cause a total blackout; if the charger is receiving power, the LED should at least attempt to flash or stay solid red when a battery is inserted.

To confirm the root cause, first isolate the power source. Many users plug these chargers into overloaded power strips or aging GFCI outlets in garages that have tripped. If the LED remains dark even when plugged into a known-working interior wall outlet, the issue is either the charger's internal circuitry or the power cable itself. Specifically, check for "pinching" where the cord enters the charger housing, as this is a common failure point for the thin-gauge wires used in these units.

How to Fix It

Follow these steps to isolate and resolve the power failure:

1. Isolate the Power Source: Unplug the charger from any extension cords or surge protectors. Plug the unit directly into a 120V AC wall outlet. If you are using a GFCI outlet (the ones with the "Reset" button), press the Reset button firmly to ensure the circuit is active.
2. Inspect the Battery Terminals: Remove the 20V Max battery from the charger. Inspect the metal contact rails on the battery for carbon buildup, oxidation, or debris. Use a cotton swab dipped in 90% isopropyl alcohol to clean the gold-plated contacts on both the battery and the charger's sliding rails.
3. Check for Cord Continuity: Inspect the entire length of the power cord for nicks, frays, or flat spots where the cord may have been crushed by a tool chest or workbench. If you have a multimeter, set it to the continuity (ohms) setting and test from the plug prongs to the internal connection points if the housing is open.
4. Perform a Hard Reset: Unplug the charger from the wall for at least 10 minutes. This allows any internal capacitors to discharge and can sometimes reset a "latched" thermal protection circuit that has shut down due to overheating.
5. Reseat the Battery: Slide the battery into the charger with a firm, decisive motion. Ensure the locking tabs click fully into place. A loose connection will prevent the charging circuit from completing, leaving the LED dark.

If That Didn't Work

• Test with a Secondary Battery: If you have another 20V Max battery, insert it. If the light comes on with a different battery, the original battery has a "dead cell" or a blown internal protection circuit (PCM), which prevents the charger from recognizing the battery entirely.
• Verify Charger Output: Using a digital multimeter set to DC voltage, carefully probe the output terminals of the charger (without the battery inserted). You should see a voltage reading close to 20V-21V. If the reading is 0V, the internal transformer or rectifier has failed and the charger must be replaced.
• Check for Blown Internal Fuse: If you are comfortable with electronics, open the charger casing to check for a blown glass fuse or a burnt capacitor. Look for a "fishy" smell or blackened components on the PCB. If the board is charred, the unit is non-repairable.
• Try a Different DeWalt Charger: Borrow a compatible 20V Max charger from another DCD series tool. If the battery charges on a different unit, your charger is defective. If it still won't charge, the battery's internal fuse is blown.

Heads Up

• Avoid Extension Cords: Never use a thin, household extension cord for charging. This can cause a voltage drop that prevents the charger from initiating the cycle or causes the unit to overheat and trip the thermal fuse.
• Temperature Control: Do not charge batteries that are extremely hot (immediately after heavy use) or freezing cold. The DCD771 charger has a temperature sensor; if the battery is outside the operating range, the charger may refuse to start.
• Storage Warning: Store your batteries at roughly 50-70% charge if you aren't using them for several weeks. Letting a 20V battery drop to 0% can cause the voltage to fall below the "threshold," making the charger think the battery is dead and refuse to light up.
• Dust Management: Keep the charger vents clear of sawdust and metal shavings. Debris inside the charger can cause short circuits or overheating, leading to permanent LED and circuit failure.