Metabo Cordless Drill Motor Replacement & Battery Diagnostics Guide: Don’t Scrap It, Fix It!

I am a firm believer that just because a component fails, the entire tool shouldn’t be destined for the bin. If your Metabo cordless drill suddenly lost power, stopped spinning, or showed signs of a burnout, chances are you have a failed motor.

This guide, based on our latest video which you can see it above, will walk you through the proper way to diagnose the battery, test the trigger switch, and perform a full motor replacement on your cordless drill, often for less than the cost of a tank of petrol!

Tools & Equipment for the Job 🛠️

Before you begin, ensure you have the correct equipment. We’re keeping this simple and accurate:

• Digital Multimeter (DC Voltage & Continuity): Essential for reading battery voltage and testing components. (Here is the Amazon affiliate link to get a new multimeter.)

• Probing Aids: Crocodile clips and custom jump wires (with spade terminals) are critical. They allow you to securely clamp onto connections, keeping your hands free and ensuring proper contact in tight battery cavities. (Here is the Amazon affiliate link to get a crocodile clip.)

• Torx Screwdriver Set (T10): Many manufacturers use specialized Torx safety screws with a small pin in the center to deter tampering. Ensure your set includes the appropriate safety tips for disassembly. (Here is the Amazon affiliate link to get a torx safety set.)

• Soldering Iron & Desoldering Braid: The motor wires are often soldered directly, requiring proper desoldering and resoldering. (Here is the Amazon affiliate link to get a desoldering station.)

• Pin Nose Pliers & Screwdrivers (Normal/Phillips): For manipulation and general disassembly.

• Miniature Jump Leads: Useful for temporarily connecting the battery to the open cordless drill to test live components.

• Flux and Solder: For a robust electrical connection on the new motor tags.

• Heat Shrink Tubing: To insulate and protect the new motor connections.

Step 1: Diagnosing the Cordless Drill’s Battery Pack (The Foundations)

Before opening the cordless drill, rule out a simple battery issue. Understanding the construction is key to diagnosis.

The Physics of Lithium-Ion Cells

• Series Connection (Voltage): Cells are stacked positive to negative, like building blocks, to increase the voltage. A typical 10.8V battery (nominal) uses three cells in series (3 x 3.6V ≈ 10.8V), giving a fully charged voltage of roughly 12.4V.

• Parallel Connection (Capacity): Cells are connected side-by-side (in parallel) to increase the amp-hour (Ah) capacity, making the battery last longer without increasing the voltage (like widening the foundations of the building block structure).

How to Check Your Battery Voltage

1. Set your multimeter to DC Voltage.
2. Use your custom jump leads to connect securely to the positive and negative terminals of the battery pack.
3. For a good battery, you can expect to see a voltage near or above 12.4V (for a 10.8V nominal pack). However, if the voltage is too low (e.g., 11V), the charger should initiate a charge.

The Battery Management System (BMS)

The BMS is a safety feature that protects you and the battery from thermal runaway (fires). If one cell is damaged or dead, the total voltage drops significantly. For instance, if an 18V battery (5 cells in series) drops to 15V, the charger will often refuse to initiate a charge because it detects a fault and cannot safely apply the full charging voltage. If the charge light stays green or doesn’t flash, the BMS has detected a serious fault.

Step 2: Disassembling the Cordless Drill Body

1. Remove Accessories: Start by removing the belt clip at the back. It often clips into the casing and will prevent separation.
2. Locate Screws: Carefully inspect the casing. Some screw holes may be covered by small plastic inserts that need to be carefully pried out with a sharp object.
3. Remove Screws: Use the correct Torx or Phillips driver. Pay attention if any screw is longer than the others, and note its original location. (On this Metabo model, all screws were the same length).
4. Split the Casing: Gently and carefully prize the two halves of the plastic casing apart. Be mindful of any internal clips that may be holding them together.

Step 3: Testing the Trigger Switch

Before ordering a motor, we need to confirm the trigger switch is functional and sending voltage.

1. Visual Check: Insert a battery and press the trigger. If the work light comes on, it’s a strong indication that the switch mechanism is receiving power.
2. Voltage Check: Firstly, you need to connect your miniature jump leads and multimeter leads to the two wires that lead directly to the motor tags. Then, set the meter to DC Voltage and press the trigger. You should read the battery voltage (e.g., 12V). This confirms the trigger is working. After that, flip the direction switch (Forward/Reverse). The reading on the meter should now show a minus symbol (-) next to the voltage. This confirms the switch is successfully reversing the polarity to change the direction of motor rotation.

If the trigger is supplying voltage, the fault is definitively the motor.

Step 4: Cordless Drill’s Motor Identification and Sourcing

Our old motor showed internal failure, indicated by fragments of steel/metal debris visible on top of the motor casing.

• Locate the Part Number: Manufacturer identification marks are often hidden. If you can’t see a number, try rotating the case halves or dismantling the drill from the opposite side.

• The specific number identified on this Metabo cordless drill motor was: 31700510.

• Searching this number on online retailers (like Amazon) will lead you directly to the correct replacement motor, which in this case was sourced for around £8.

Step 5: Replacing the Motor

Extraction

1. Desolder: Using your soldering iron and desoldering braid/wick, heat up the joints and carefully remove the existing solder. Once the solder is melted, pull the wires away from the motor tags.
2. Remove: Carefully lift the old motor away from the gearbox assembly.

Installation

1. Prepare the Gearbox: Apply a very small touch of grease to the exposed cogs to prolong the life of the gearbox. Do not over-grease.
2. Insert New Motor: Drop the new motor into position, ensuring the pinion gear on the motor lines up perfectly with the first cog inside the gearbox unit.
3. Solder: First things first, you should clean up the existing wires, trimming off any damaged sections. You may need to add a piece of heat shrink tubing to any exposed wire. Then, you will need to apply a small amount of flux to the motor tags. After that, you should feed the wire through the small hole on the motor tag, heat the tag, and apply solder. You must achieve a clean, solid electrical connection. Finally, you can slide the heat shrink tubing over the exposed terminals and shrink it into place.

Step 6: Reassembly and Test

1. Check Alignment: Before closing the case, apply a battery and test the unit. Place your finger on the top of the motor and gearbox to ensure there’s no movement and all the cogs are lining up correctly. Test both rotation directions using the switch. Then, test the high/low gear selector.
2. Reassemble: Carefully place the other half of the casing onto the cordless drill body. Ensure all wiring is tucked away and will not be pinched or snagged when you screw the case together.
3. Final Test: Insert the screws, replace the belt clip, and congratulations you’ve got a newly repaired drill and successfully kept a valuable tool out of the landfill!

We hope this guide has given you the confidence to tackle a repair on your Metabo cordless drill. For a full visual walkthrough and dismantling process, make sure to check out the video on our YouTube channel.

If you have any questions about your appliances, please provide your brand, full model number which is written on the identification label, and a detailed description of the issue. Please visit our Contact Us page and make sure you fill out the request for what your problem is. A video shoot of the problem would be perfect as well.

If you found this guide helpful, consider supporting us by clicking on the Buy Paul a Beer link to help us continue making repair videos and guides.

Tools & Parts Used in This Video: (You can use these Amazon affiliate links below to help support our channel.)

1. Multimeter
2. Crocodile Clip Adapters
3. Torx Safety Set
4. Desoldering station
5. Desoldering Wire
6. Replacement Motor (317005100)