June 1, 2016

How to replace a chain-drive garage door opener RPM sensor

By Lyle Weischwill
How to replace a chain-drive garage door opener RPM sensor

This DIY repair guide explains how to replace the RPM sensor on a chain-drive garage door opener. The RPM sensor detects motor speed. If the RPM sensor breaks, the garage door only moves 6 to 8 inches at a time and the LED light flashes 5 times. Replace the RPM sensor with the manufacturer-approved replacement part.

This basic procedure works for common Craftsman, LiftMaster and Chamberlain garage door openers.

Quick links
Tools required
Step ladder
Work table
Needle-nose pliers
Socket wrench set
Nut driver set
Work gloves
Repair difficulty
Time required
60 minutes or less
Repair difficulty
Time required
60 minutes or less
Replacing the RPM sensor on a garage door opener

This video explains how to replace the RPM sensor on a garage door opener.

Instructions

  1. 01.

    Disconnect power

    Use a step ladder to access the garage door opener’s power cord and motor unit.

    Unplug the garage door opener.

    Unplug the garage door opener.

    Unplug the garage door opener.

  2. 02.

    Take the garage door opener down

    Position a work table near the area under your motor unit to hold the garage door opener during the repair.

    Pull the emergency release rope to release the trolley from the garage door.

    Shut the garage door if it's not already closed.

    Remove the fastener ring from the straight door arm connected to the outer trolley.

    Pull out the clevis pin while supporting the straight arm to disconnect the garage door from the outer trolley.

    Lower the straight and curved arms down and rest them against the garage door. Use a helper if necessary.

    Open the light cover to access the wall control and safety sensor wires connected to the motor unit.

    Take a digital photo of the wall control and safety sensor wires connected to the motor unit. You'll refer to the photo later when reconnecting the wires.

    Disconnect the wall control and safety sensor wires from the motor unit.

    Close the light cover.

    Remove the nuts, bolts, and lock washers that secure the motor unit to the ceiling bracket. Support the motor unit with one hand as you remove the last bolt from the ceiling bracket.

    Carefully lower the motor unit down and rest it securely on top of the step ladder.

    Climb down the stepladder, lower the motor unit down and rest it on your work table.

    Move your stepladder by the garage door so you can remove the rail from the header bracket.

    Remove the fastener ring from the header bracket clevis pin.

    Pull the clevis pin out of the rail and header bracket while supporting the rail with one hand.

    Lower the rail and rest it on a rung of the stepladder so the rail is level with the motor unit on your work table.

    Tip: To avoid scratching a decorative garage door, remove the nuts, bolts and washers from the curved arm and carefully rest the curved arm against the door when disconnecting the garage door from the outer trolley.
    Tip: You may want to have a helper assist you when taking the garage door opener down.
    Remove the motor unit bolt.

    Remove the motor unit bolt.

  3. 03.

    Remove the RPM sensor

    Remove the light covers and light bulbs from the motor unit.

    Flip the motor unit over, remove the screws from the motor unit cover and pull the cover off.

    Unplug the RPM sensor wire harness.

    Remove the interrupter cup from the motor shaft.

    Release the RPM sensor from the mounting clip and remove it.

    Tip: The left-side motor unit cover doesn't have the wiring connections for the wall control and safety sensors.
    Remove the motor unit cover.

    Remove the motor unit cover.

  4. 04.

    Install the new RPM sensor

    Push the new RPM sensor into the mounting clip, locking the sensor into place.

    Connect the RPM sensor wire harness to the new sensor.

    Reinstall the interrupter cup on the motor shaft.

    Reinstall the motor unit cover, securing it with the mounting screws.

    Reinstall the light bulbs and light covers on the motor unit.

    Install the new RPM sensor.

    Install the new RPM sensor.

  5. 05.

    Reinstall the garage door opener

    Reconnect the rail end to the header bracket using the clevis pin and fastener ring.

    Position your step ladder under the motor unit ceiling bracket and carefully set the motor unit on top of the step ladder.

    Climb the step ladder and reinstall the motor unit to the ceiling bracket using the nuts, bolts and lock washers.

    Open the light cover to access the wall control and safety sensor terminals on the motor unit.

    Using your digital photo for reference, reconnect the wall control and safety sensor wires to the motor unit.

    Close the light cover.

    Reconnect the straight door arm to the outer trolley using the clevis pin and fastener ring.

    Re-engage the trolley.

    Tip: Reconnect the curved door arm to the straight door arm using the bolts, lock washers and nut if you disconnected the curved arm from the straight arm when freeing the garage door from the outer trolley.
    Reconnect the rail to the header bracket.

    Reconnect the rail to the header bracket.

  6. 06.

    Reconnect electrical power

    Plug in the garage door opener.

Warning: Undertaking repairs or maintenance to appliances or power equipment can be hazardous. Should you choose to undertake repairs or maintenance, you are assuming the risk of injury to your person or property. In an effort to reduce the risk, use the proper tools and safety equipment noted in the applicable guide and follow all instructions. Do not proceed until you are confident that you understand all of the steps and are capable of completing the repair. Some repairs or maintenance, however, should only be performed by a qualified technician.

Symptoms common to all garage door openers

Choose a symptom to see related garage door opener repairs.

Main causes: loose fasteners, broken brackets, need preventive maintenance, worn drive gears, loose or worn belt, loose chain
Main causes: safety sensor beams blocked, safety sensors not aligned, downforce setting needs adjustment, damaged garage door tracks
Things to do: check garage door travel, tighten brackets and fasteners, test safety sensors, check travel limits and force limits
Main causes: faulty logic control board, bad RPM sensor, broken gears in the drive system, bad drive motor
Main causes: garage door opener misaligned, travel limits need adjustment, bad travel limit switches, faulty logic control board
Main causes: neighbor's remote programmed at the same time as yours, faulty wall control wiring, bad wall control unit
Main causes: radio interference, weak remote batteries, sunlight interference with safety sensor beams, safety sensors need adjustment
Main causes: garage door locked, damaged garage door tracks, up-force setting needs adjustment, RPM sensor failure, bad drive motor

Repair guides common to all garage door openers

These step-by-step repair guides will help you safely fix what’s broken on your garage door opener.

June 20, 2016
By Lyle Weischwill
How to replace a garage door opener battery

The garage door won't move during a power outage if the battery is dead. Here’s how to replace it.

Repair difficulty
Time required
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January 6, 2016
By Lyle Weischwill
How to replace a garage door opener drive belt

A damaged or broken belt on your garage door opener could be the reason it won’t move the door. Here’s how to fix it.

Repair difficulty
Time required
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How to replace a chain-drive garage door opener drive and worm gears

If your garage door won’t move, the drive and worm gears could be broken. This guide will help you replace the gears.

Repair difficulty
Time required
 60 minutes or less

Articles and videos common to all garage door openers

Use the advice and tips in these articles and videos to get the most out of your garage door opener.

May 11, 2018

Garage door won't move: motor and travel troubleshooting video

By Sears PartsDirect staff

Diagnose and repair problems if your garage door won’t move and the motor unit indicator light flashes 5 times.

October 26, 2016

How to repair broken or damaged wires video

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Learn how to repair broken, frayed or damaged wires in your appliances.

March 4, 2015

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Learn what maintenance a garage door opener needs, and when to perform the maintenance.