Skip to product information
1 of 1

The Genie Company

Optical Encoder (RPM Sensor) 39155R.S- DC Screw Drive Models

Optical Encoder (RPM Sensor) 39155R.S- DC Screw Drive Models

Regular price $24.99 USD
Regular price Sale price $24.99 USD
Sale Sold out

The Optical Encoder is also known as the RPM sensor. The 39155R.S is used in certain model Genie screw drive garage door openers. (See below list for compatibility by model) Replacing this part may resolve any issue of short traveling problems or limits drifting on the garage door opener. 

  • Compatible with models; TriloG™1200 (3064), TriloG™ 1500 (4064), PowerMax® 1200 (3062), MachForce (4063), PowerMax® 1500, Excelerator® 1000, Excelerator® II (4062)
  • If your garage door opener model is not on this list, please contact Genie for additional compatibility questions
  • Genuine Genie Replacement Part 

SKU: 39155R.S

In Stock! Usually ships within 24 hours.

ASK A QUESTION View full details
Optical Encoder (RPM Sensor) 39155R.S- DC Screw Drive Models
Optical Encoder (RPM Sensor) 39155R.S- DC Screw Drive Models


Ask a Question
  • I have 4063 did not see that model number on your optical encoder. My door will not hold a program. I set it and works fine for a hour sometimes a day. The door will close and it keeps trying to push the door down bending the rail.

    Yes, the 4063 is compatible with the Optical Encoder (RPM Sensor) 39155R.S- DC Screw Drive Models and this would likely be the issue based on your symptom.

  • I have a TriloG 1500 4064. The door stops at ~4 foot on opening. I reset the limits and the door goes up and down once. At the next "open", it stops at 4 foot again. I believe it may be dust on the optical reader (I took the case off and it was VERY dusty). Can I get a copy of the optical reader install instructions so I can take it apart and clean it? If that doesn't work, I'll order a new one Thanks

    You can view the instructions for replacing the optical encoder here.

PDF Printable version of instructions for replacing the 39155R.S Optical Encoder 

39155R.S DC Opto Sensor Assembly Replacement, for Screw Drive Openers

This repair will require removal of the unit from it’s mounting hardware and repairs made on a clean work surface. Refer to your Owners Manual and/or Installation Poster for proper assembly and carefully read and understand all warnings and cautions pertaining to your unit.



1. Before pulling emergency release cord, make certain people and objects are clear of door opening. Pull emergency release cord on carriage to disengage opener to close door if necessary. If unable to lower door using opener, use extreme caution manually closing door.

2. Unplug the garage door opener power cord from power receptacle.

3. Open lens cover by pressing middle tab inward to swing down and remove light bulbs. FIG. 1.

4. Mark wires to help facilitate replacement and remove wall control and Safe-T-Beam wires from terminal block located on side of opener FIG. 1. Use small common screwdriver to press in on orange tabs while gently pulling wires from block.

39155R.S Optical Encoder replacement instructions


5. Remove network and battery backup harnesses from the front of opener (if applicable).

6. Remove the cotter pin & clevis from door arm to separate the garage door from the garage door opener. FIG. 2.

Optical encoder 39155R.S replacement instructions

7. Remove motorhead and rail assembly from mounting brackets/ hardware and set on a clean work surface or floor.

Note: Be aware of the motion detector bulb on bottom of powerhead cover (if
equipped). Do not set operator weight on this bulb.

8. Remove the 6-7/16” self-tapping bolts from the rail/motor mounting straps and pull rail from motorhead. FIG.3. Set the screw drive rail assembly aside.

replacing the optical sensor 39155R.S for Genie screw drive model garage door openers

9. Remove two 5/16” screws securing powerhead cover to chassis and swing open to expose control board. Fig. 4.
NOTE: Do not remove control board from cover, shown for clarity only.

39155R.S Optical Encoder replacement instructions
10. Unplug these harnesses from the control board. FIG. 5.
• Motor harness
• Opto harness
• AC in harness
• Green ground wire to chassis from light harness (if equipped).

Genie Screw Drive Optical Encoder replacement

11. Powerhead cover can now be removed from opener chassis.

12. Remove three motor mounting bolts from motor frame FIG. 6. Remove motor assembly.

39155R.S Optical encoder replacement for Genie screw drive openers

13. Using an 11/32 socket or nut driver, press down on encoder wheel mounting clips while pulling wheel off of spline shaft. FIG. 7.

14. Remove and retain screw(s) holding encoder to motor frame FIG. 8.

15. Remove and retain e-ring holding motor gear to motor shaft. FIG. 8.

16. Remove and retain motor gear. FIG. 8.

Genie 39155R.S screw drive optical encoder replacement instructions

17. Install replacement encoder assembly with screw(s).

18. Install motor gear and e-ring to motor shaft.

19. Snap encoder wheel into place. (Interrupter fins face encoder.)

20. Install motor assembly in reverse order.

Note: Be certain to install all harnesses in the correct position being sure to install with locking tabs facing each other. (Detailed in FIG. 5 - Step 10)

21. Hang powerhead cover to chassis to install harnesses. Including green ground wire to chassis (if equipped)

HARNESS NOTE: Check the type of circuit board installed in your opener (see FIG. 9). Use appropriate harness included
with this kit.

39155R.S Screw drive optical encoder replacement instructions for Genie garage door openers

22. Install powerhead cover onto chassis using 2- 5/16” screws.

23. Install rail to motor head assembly using the screw drive coupler, mounting flange and 6-7/16” self-tapping screws.

24. Reinstall opener assembly in reverse order as removed. Reference your owners manual and installation poster.

25. Install the wall console and Safe-T-Beam® wires. Install battery backup and/or network harnesses if applicable.

26. Install the light bulbs and close the light lens cover.

27. Plug the garage door opener into the power receptacle.

28. Clear and reprogram the limit setting controls per the garage door opener owners manual.

  • Shipping Truck

    Free Shipping

    We offer FREE shipping and handling on all orders that total over $17.99 and are shipped to a US address. All orders are shipped using UPS ground, directly from The Genie Company.

  • Genuine Genie Accessories and Parts

    Genuine Replacements

    Buying GENUINE Genie accessories and parts guarantees that you are getting quality OEM materials backed by a Genie warranty.

  • Customer support chat


    Need assistance? We are here for you! We offer a wide range of customer support options including contact by phone or email, web chat services with a live agent, and a robust support section also located on our website.  All customer care teams and services are based in the USA.