Simplex 900 Series Mechanical Pushbutton Lockset

Aug. 1, 2005
We will install, change the combination, clear a lost combination, and troubleshoot some common problems on this workhorse of a pushbutton lock.

Pushbutton access control was one of the first alternatives to mechanical key control for entry doors. The ability to unlock a lock by pressing numbered buttons eliminated problems associated with the issuance, control, and collection of keys. The Simplex® 900 Series was one of the first mechanical pushbutton locks.

The Simplex 900 Series mechanical pushbutton locks are designed for light commercial and residential applications. They are equipped with a friction clutch that disconnects the outside thumbturn from the lock housing when excessive force is exerted. These field-reversible, rim type auxiliary locks are available having a spring latch with deadlocking trigger or one-inch throw deadbolt. The combination can be changed without having to remove the lock from the door or disassemble the lock.

The surface-mounted Simplex 900 Series mechanical pushbutton lock has five buttons through which the combination is entered. The combination can be any variation from one up to using all five buttons in sequence. Simplex was developed with the capability of pressing either one button or multiple buttons simultaneously. For example, the default combination is pressing "2" and "4" simultaneously, and then the "3".

There are approximately 500 combinations when each button is fully depressed and additional 500 theoretical combinations when buttons are only partially depressed.

Note: Before entering the combination, always turn the outside operating knob counterclockwise until it stops. This clears the combination chamber.

Once the combination has been entered in the correct sequence, turning the outside operating knob clockwise retracts the spring latch or deadbolt. The deadlocking spring latch models automatically relock when the door closes. The deadbolt models manually relock. Egress is attained using the interior thumbturn, which is free at all times.

For this article, we will install, change the combination, clear a lost combination, and troubleshoot some common problems. We will be working with Simplex Part # 9040000-26D-41, a deadbolt lock with no options.

Remember: For retrofit installations, the exterior faceplate can cover existing 2-1/8" diameter cross bore openings.

The Simplex 900 Series locks are surface-mounted. Follow these steps to install the lock.

Step 1. Determine the location for the lock. Kaba Access Control recommends the Simplex 900 Series be 8 to 10 inches above the existing lockset.

Step 2. Use the included template to locate the 5 cross bore openings. An additional hole is required if the lock has key override. The backset is determined by the handing of the door.

Step 3. Drill the two cross bore openings. When drilling a cross bore hole in a wood or hollow metal door, do not drill completely through the door. Stop drilling once the pilot bit or drill tip has exited the obverse side of the door. Remove the drill and begin to drill from the other side. This will ensure a more accurate cross bore opening and will stop the bit from causing damage to the face of a wood door.

Step 4. Drill the three mounting screw holes approximately 1/2"deep in a wood door, or through the skin of a hollow metal door. Remove any burrs prior to installation.

Step 5. From the rear of the door, slide the 900 Series lock assembly through the cross bore openings. Make certain the lock is flush against the face of the door. For doors that do not have an even mounting surface, use an adjustable riser plate, part number 74468.

Step 6. Install the three 1-1/2" long Phillips head mounting screws.

Step 7. On the front side of the door, place the holding bracket onto the keypad assembly with the slotted legs engaging the aligning pin. Make sure the bracket does not cover the thumbturn opening.

Step 8. Attach the holding bracket onto the door using the two 1/2" Phillips head screws.

Step 9. Remove the three screws securing the lock assembly to the door. Remove the lock assembly.

Step 10. Slide the faceplate onto the holding bracket. Make sure the faceplate aligns with the cross bore opening.

Step 11. Insert the lock assembly from the rear of the door into the cross bore openings. Position and rotate the thumbturn to the vertical position to accommodate the shaft of the ball bearing clutch assembly.

Step 12. Install the three mounting screws while keeping the lock assembly in place.

Once the lock has been installed, test the operation with the door open. If there is a problem, the lock can be easily accessed.

Step 1. With the door open, turn the outside thumbturn counterclockwise to the stop position. This clears any numbers that have been entered into the combination chamber.

Step 2. Enter the combination. The factory preset combination is two and four pressed together, then three. Each time a button or buttons are pressed, you should hear distinctive clicks.

Step 3. If the operating combination has been properly entered, turning the outside thumbturn clockwise will retract the deadbolt. Note: If at any time a mistake is made, turn the outside thumbturn counterclockwise to clear the combination chamber.

To extend the deadbolt from the outside, turn the thumbturn counterclockwise until it stops.

Changing The Combination

Most Simplex pushbutton locks have the same factory default combination. It is important to change the factory default combination once the lock has been installed.

The combination can be changed without removing the lock from the door. Choose the new combination carefully before changing. Remember: A combination cannot use any number more than once. When setting up a new combination, two or more numbers can be pressed simultaneously as part of the combination.

When changing the combination of a Simplex 900 lock, have the door open to prevent accidental lockout. This is especially important when changing a deadbolt model combination because turning the deadbolt model's thumbturn to clear the chamber causes the bolt to extend and lock in position.

Step 1. Clear any entry by turning the outside thumbturn to the left (counterclockwise) until it stops. Then release the thumbturn.

Step 2. Remove the hex head screw from end of the lock housing using a 1/8" hex wrench.

Step 3. Enter the operating combination. A slight click should be heard as each button is depressed.

Step 4. Insert the long end of the Allen wrench into the screw hole and gently depress the internal lockout slide until there is a slight click. Do not force. Remove the hex wrench from the lock. Depressing this slide permits the combination to be changed.

Step 5. Clear the combination by turning the outside thumbturn counterclockwise to the stop position. Then release the thumbturn.

Step 6. Enter the new combination by carefully depressing the buttons. A slight click should be felt as each button is depressed.

Step 7. Turn the outside thumbturn clockwise to the stop position to set the new combination. Then release the thumbturn.

Test the new combination at least three times before closing the door. Reinstall the hex head screw.

Clearing a lost combination

The following instructions enable the user to set a new combination when the combination is no longer available. The only way to determine an unknown combination is to remove the combination chamber from the lock, which requires disassembly of the lock.

Step 1. Remove the lock from the inside of the door by removing the three Phillips head screws.

Step 2. Remove the two screws and flange washers from the opposite ends of the center plate containing the barrel assembly from the lock housing.

Step 3. Lift out the center plate.

Step 4. Remove the two screws securing the gear plate.

Step 5. Carefully lift out the gear plate and disconnect the armature from the sector cam.

Step 6. Remove the two screws securing the combination chamber in the housing.

Step 7. Lift the combination chamber out of the housing.

Step 8. Use a small straight slot screwdriver to remove the "e" ring from the unlocking slide stud.

Step 9. Gently lift the end of the unlocking slide over the unlocking slide stud. The unlocking slide is connected and under spring pressure. Once disconnected, carefully swing the unlocking slide to clear the gears.

Step 10. Press the lockout slide to clear the combination.

Step 11. Turn each gear until its pocket aligns with the opening for each of the unlocking slide toes.

Step 12. Once all five gears are aligned, install the unlocking slide so the five toes enter the five gear pockets.

Step 13. Attach the "e" ring onto the unlocking stud.

Step 14. Install the combination chamber into its housing.

Re-assemble and install the Simplex 900 Series lock into the door before trying to enter a combination.


Condition: The deadbolt or latch retracts when the thumbturn is rotated clockwise and you have not entered your combination.

Problem: The lock has been set to a zero combination.

Solution: Reset the combination.

Condition: The bolt will not retract when proper combination is pressed and thumbturn is rotated to the unlocked direction.

Problem: The buttons were probably not fully pressed when entering the combination.

Solution: Turn the thumbturn to the stop position to clear the combination. Re-enter the combination pressing each button until there is a click sound. Rotate thumbturn to retract the bolt.

Condition: Turning outside thumbturn always retracts latch/bolt without depressing any buttons.

Problem: Lock has a "zero" combination.

Solution: Enter a new combination. However, do not enter the existing combination.

The Simplex 900 Series pushbutton locks are manufactured of metal, having a cast rear housing and a brass trim plate. The exterior thumbturn is clutch protected. The numeric pushbuttons are vandal resistant, manufactured of anodized aluminum. The locks are available in Satin Brass or Satin Chrome.

For more information, contact your local locksmith wholesaler or Kaba Access Control, 2941 Indiana Ave, Winston-Salem, NC 27105. Telephone: 800-849-8324. Fax: 800-346-9640 .Website:

Time for new installation:
30 to 60 minutes

One year

Tools required:

  • 1-5/8" diameter hole saw
  • 3/4" and 1/8" diameter drill bit
  • 1/8" hex wrench
  • drill motor
  • chisel
  • punch
  • screwdrivers
  • hammer