How to Identify and Replace Faulty Components in a Cordless Drill Machine – Dongcheng DCJZ1202E Guide

How to Identify and Replace Faulty Components in a Cordless Drill Machine – Dongcheng DCJZ1202E Guide

A cordless drill is made up of several key components working together. When your drill stops working properly, replacing the faulty part is often much cheaper than buying a new machine.

In this guide, we'll use the Dongcheng DCJZ1202E Cordless Drill as an example. This popular 12V cordless drill features a 10mm chuck, 35Nm torque, 2-speed gearbox, and lithium-ion battery system.

The most commonly replaced parts are:

  • Switch Assembly

  • Gearbox with Chuck Set

  • Motor

  • Battery

  • Charger

Let's look at how to identify which component has failed.

1. Faulty Battery

Common Symptoms

  • Drill does not turn on.

  • LED indicator does not light up.

  • Battery charges for only a few minutes.

  • Drill runs for a few seconds and stops.

  • Power drops significantly under load.

How to Test

  1. Fully charge the battery.

  2. Insert it into the drill.

  3. Check if the battery indicator shows charge.

  4. Try another known-good battery if available.

When to Replace

Replace the battery if:

  • It does not charge.

  • It charges but discharges quickly.

  • The battery becomes excessively hot during use or charging.

  • The drill works normally with another battery.

2. Faulty Charger

Common Symptoms

  • Battery never reaches full charge.

  • Charger indicator remains off.

  • Charger becomes unusually hot.

  • Multiple batteries fail to charge.

How to Test

  1. Connect the charger to a working power outlet.

  2. Observe charging indicators.

  3. Try charging another battery.

  4. If available, test the battery with a different charger.

When to Replace

Replace the charger if:

  • No charging indicators appear.

  • Multiple batteries fail to charge using the same charger.

  • The battery charges normally with another charger.

3. Faulty Switch Assembly

The switch is responsible for speed control, forward/reverse operation, and supplying power to the motor.

Common Symptoms

  • Drill works intermittently.

  • Motor starts only when trigger is pressed very hard.

  • Variable speed control stops working.

  • Reverse or forward function fails.

  • LED light may work but motor does not run.

How to Test

  1. Ensure battery is fully charged.

  2. Listen carefully while pressing the trigger.

  3. If there is no motor response despite a good battery, the switch may be faulty.

  4. Check for burnt smell around the trigger area.

When to Replace

Replace the switch if:

  • Battery and motor are confirmed good.

  • Trigger operation becomes inconsistent.

  • Speed control fails completely.

4. Faulty Motor

The motor converts electrical power into rotation.

Common Symptoms

  • Burning smell from the drill.

  • Excessive sparking.

  • Motor becomes extremely hot.

  • Drill runs slowly even with a fully charged battery.

  • Motor produces humming sound but does not rotate.

How to Test

  1. Check that battery and switch are working properly.

  2. Remove the housing.

  3. Inspect motor terminals and wires.

  4. Look for burnt windings or discoloration.

When to Replace

Replace the motor if:

  • Windings are burnt.

  • Motor has excessive sparking.

  • Motor shaft is seized.

  • Armature or brushes are damaged beyond repair.

5. Faulty Gearbox or Chuck Assembly

The gearbox transfers power from the motor to the chuck while providing torque multiplication.

Common Symptoms

  • Motor spins but chuck does not rotate.

  • Clicking or grinding noise.

  • Drill loses torque.

  • Chuck slips during drilling.

  • Gear selection stops working.

How to Test

  1. Remove the battery.

  2. Rotate the chuck manually.

  3. Listen for abnormal noises.

  4. Check for excessive play in the chuck.

When to Replace

Replace the gearbox with chuck set if:

  • Internal gears are worn.

  • Chuck no longer grips drill bits securely.

  • Gearbox produces grinding sounds.

  • Output shaft is damaged.

Basic Replacement Procedure

Safety First

Always:

  • Remove the battery before disassembly.

  • Work on a clean table.

  • Keep screws organized.

  • Take photos during disassembly for reference.

Opening the Drill

  1. Remove the battery.

  2. Unscrew all housing screws.

  3. Carefully separate the two housing halves.

  4. Note the position of wires and components.

Replacing the Faulty Part

  • Switch: Disconnect wires and install the new switch.

  • Motor: Remove motor connections and install the replacement motor.

  • Gearbox: Remove gearbox assembly and fit the new gearbox with chuck set.

  • Battery: Simply replace with a compatible battery.

  • Charger: Replace with the correct charger model.

Reassembly

  1. Reinstall all components.

  2. Ensure wires are routed correctly.

  3. Close the housing.

  4. Tighten screws evenly.

  5. Test the drill before regular use.

Common Troubleshooting Chart

Symptom Likely Fault
Drill completely dead Battery, Charger, Switch
Battery not charging Charger or Battery
LED works but motor doesn't Switch or Motor
Motor runs but chuck doesn't spin Gearbox
Drill lacks power Battery or Motor
Grinding noise Gearbox
Trigger works intermittently Switch
Excessive heat and burning smell Motor

Genuine Dongcheng DCJZ1202E Spare Parts

Using genuine replacement parts helps maintain performance, safety, and reliability. For the Dongcheng DCJZ1202E, the most commonly replaced spare parts include:

  • Switch Assembly

  • Gearbox with Drill Chuck Set

  • Motor

  • Battery

  • Charger

You can find genuine Dongcheng DCJZ1202E spare parts online at TrendTools and restore your cordless drill to working condition without replacing the entire machine.

Final Thoughts

Most cordless drill failures can be traced to one of five components: battery, charger, switch, motor, or gearbox. By identifying the symptoms correctly, you can quickly determine which part needs replacement and get your drill back to work at a fraction of the cost of a new machine.

If you're unsure which part has failed, contact the TrendTools support team with photos or a video of the issue, and we'll help you identify the correct spare part for your Dongcheng cordless drill.

Back to blog