How to Test a Cordless Drill Trigger Switch With a Multimeter

How to Test a Cordless Drill Trigger Switch With a Multimeter

ByKen

How to Test a Cordless Drill Trigger Switch With a Multimeter

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The person typing how to check a cordless drill trigger switch with a multimeter wants to know whether the trigger has failed, or whether the drill has a battery, motor or wiring fault. A multimeter can show whether the trigger contacts open and close as the trigger moves. It cannot show the speed control curve, the reversing action or the motor’s health. This guide covers battery removal, the continuity steps, how to read the trigger, and where a bench check stops being useful.

Quick answer

  • Remove the battery pack before you test. Never test the trigger with the pack attached.
  • Use continuity mode or the lowest ohms range, with the red lead in VΩ and the black lead in COM.
  • With the trigger released the switch should be open, and with it pressed fully the switch should close.
  • An open reading when pressed, or a closed reading when released, points to a switch fault.
  • A passing trigger does not clear the motor, the brushes, the electronics or the battery. Check those separately.

Safety first

A cordless drill runs from a battery pack that can deliver a large current. The trigger switch sits in the same circuit as the battery and the motor. The first step is always to take the battery pack out of the drill. Fluke’s automotive continuity article advises disconnecting battery power or isolating the circuit before testing for continuity, and that rule applies here.

Do not test the trigger with the battery in place. Do not short the battery terminals to test the switch. If the drill has a fault that produces heat, smoke or a burning smell, stop, remove the pack and do not use the tool until it has been inspected. Keep fingers clear of the chuck and the bit when the trigger is moved during the test.

What you need

  • A digital multimeter with continuity mode or a resistance range.
  • Test leads in good condition, with the red lead in the VΩ jack and the black lead in COM.
  • The drill’s service information or the screw driver that opens the housing.
  • A notepad or phone to record each trigger position and reading.

Step 1: Remove the battery and open the housing

Pull the battery pack off the drill and set it aside, away from the workbench. Open the housing with the correct screws or clips. Take photographs of the wire routing before you disconnect anything. A trigger switch usually has two or more wires and sits on a spring-loaded plunger. The wire positions matter when you reassemble the tool.

If the housing does not open with normal tools, stop. Forcing a housing can break the plastic tabs or the wiring.

Step 2: Set up the meter

Put the black lead in COM and the red lead in VΩ. Fluke’s dial page lists the COM jack as the black test lead input for all measurements, and the VΩ jack as the red lead input for voltage, resistance, diode, capacitance and temperature measurements. Turn the dial to continuity, or to the lowest resistance range if your meter has no continuity mode.

Fluke’s continuity guide says the continuity mode is common on DMMs, often combined with resistance. Check your own meter’s dial, because the labels differ by brand.

Step 3: Isolate the switch

Disconnect the trigger switch from the wiring harness, or at least one of its terminals, so the reading applies to the switch alone. Fluke’s automotive continuity article lists “Across switch terminals” as a standard test point. The idea is to measure the switch, not the motor or the wiring behind it.

Keep the wire labels with the switch. Some triggers have three terminals, with one terminal for forward and another for reverse. Identify the common terminal before you test.

Step 4: Test with the trigger released

With the trigger fully released, touch the probes to the two terminals you need to test. A normal trigger switch should read open in the released position. Fluke’s continuity guide states that a circuit is complete only when its switch is closed, and that the meter will not beep when the circuit is open. A released trigger that beeps or reads a low resistance is a sign the contacts are stuck closed.

Step 5: Test with the trigger fully pressed

Press the trigger fully and hold it in place. The contacts should close and the meter should beep or read a low resistance. Fluke’s guide notes that the meter beeps if a complete path is detected. A pressed trigger that stays open points to a worn contact, a broken internal part or a damaged plunger.

Move the trigger slowly through its travel. A switch that reads closed at one point and open at another can have a worn section or a dirty contact. Repeat the test two or three times to see whether the reading is consistent.

Step 6: Read the result

  • Open when released, closed when pressed: the switch is behaving as expected.
  • Closed when released: the contacts may be stuck or the plunger may not return. Do not use the drill until this is corrected.
  • Open when pressed: the contacts may be worn, dirty or broken. The switch is a likely cause.
  • Erratic reading: clean the contacts with an approved contact cleaner and test again. If the reading stays erratic, replace the switch.

Fluke’s continuity guide says a good fuse or closed switch should show continuity. The same rule applies to the trigger in the pressed position. Thresholds for the beep vary by meter, so read your meter’s manual.

Step 7: Check the rest of the circuit

Once the switch passes, check the wiring between the switch and the battery contacts for continuity. Fluke’s automotive continuity article describes testing a wire or a switch for breaks. A broken wire can give the same symptom as a failed switch: the drill does not run when the trigger is pressed. Check the battery contacts, the terminal blocks and the motor leads separately.

The motor, the brushes, the speed controller and the electronic board are outside the scope of a simple continuity check. If the switch passes and the drill still does not run, the fault is likely elsewhere. Test each part and record the reading.

Reassembly and a final check

Before reassembling, make sure the wires are routed as they were in the photograph. Pinched wires can short when the housing closes. Refit the housing screws without over-tightening, because over-tightening can crack the plastic. Reinsert the battery only after the housing is fully closed.

With the battery in place, test the trigger by pressing it lightly. The drill should run only when the trigger is pressed. If it runs with the trigger released, stop and remove the battery. Do not use the tool.

Mistakes to avoid

  • Testing with the battery pack attached. Remove it first every time.
  • Reading the motor and the switch together. Isolate the switch before you test.
  • Assuming a closed reading means the trigger is fine under load. A bench check does not show contact wear under a high current.
  • Forcing the housing or the plunger to get the reading you expect.
  • Replacing the switch without checking the wiring and the battery contacts.

Buying checklist for a replacement switch

  • Match the drill’s model number and the switch’s terminal layout.
  • Check the number of terminals and whether the switch has a reverse function.
  • Use a switch from the drill maker or a source that lists the same ratings.
  • Do not fit a switch with no rating information.

How we chose

This guide covers the test steps that the Fluke learning pages listed in the sources describe: setting up the meter, isolating the part, and reading continuity or DC voltage. We left out steps and numbers that these pages do not state. The sources were opened on 2026-10-27. We did not compare products or rank parts in this guide.

What we could not verify

The sources we opened do not give the contact resistance, current rating or service life of any cordless drill trigger switch. They do not describe the wiring or terminal layout of any particular drill model. They also do not state a reading threshold for a trigger switch. Check the maker’s service information for those figures. The steps here show how to read continuity, not how a specific trigger should measure.

FAQ

Can I test the trigger switch with the battery in the drill?

No. Remove the battery first. Fluke’s guidance says to isolate the circuit before continuity testing, and a drill battery can deliver a large current.

Why does my drill run even when the trigger is released?

Stop using the drill. A switch that stays closed when released can be stuck or damaged. Remove the battery and inspect the trigger and its plunger before you run the tool again.

Does a passing trigger mean the drill is safe?

No. A passing trigger shows only that the switch contacts open and close. It does not show the motor, brushes, electronics or wiring are sound.

Can I clean the contacts?

Use a contact cleaner approved for electrical switches, and follow its label. Do not use abrasive tools on the contacts.

Do I need to test the speed control?

Many triggers are variable-speed. A simple continuity check does not show the speed curve. Use the maker’s information for that.

Bottom line

Remove the battery, isolate the trigger switch, and read continuity with the trigger released and fully pressed. A switch that is open when released and closed when pressed passes this check. A switch that stays closed when released, or stays open when pressed, is a likely cause of the fault. Check the wiring and the motor before you blame the switch alone.

Related guides

Sources

  • Fluke, “A Guide to Continuity Testing with a Multimeter”, https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-for-continuity (opened 2026-10-27).
  • Fluke, “How to Perform Automotive Continuity Checks with a Multimeter”, https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-perform-automotive-continuity-checks-with-a-multimeter (opened 2026-10-27).
  • Fluke, “The Dials, Buttons, Symbols, and Display of a Digital Multimeter”, https://www.fluke.com/en-us/learn/blog/digital-multimeters/multimeter-dial-button-jacks-display (opened 2026-10-27).

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