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Simplex locks are push-button models created by Kaba that allow private areas such as homes and offices to be accessed through the entry of a numerical code. This negates the need to have keys made and also eliminates the risk of a key being lost or duplicated, though there is a master key option as well in some models. The combination can be changed at any time and only takes a few seconds. If your Simplex lock is not functioning properly, try troubleshooting it first before calling a repair technician.
Turn the bolt or knob on the lock to see if it opens without any code entered. If it does, the lock is in "zero combination." Program a new code into the lock when the door is open. The specific way of doing this varies depending on the lock model. Generally, you turn the latch or knob to the left once to reset the lock of any numerical entries. Use an Allen wrench to remove a screw from the back of the lock housing and then to depress the internal lockout slide. Turn the knob or bolt to the left one more time and then enter your new combination on the keypad. Turn the knob or bolt to the right when finished to activate the combination. Test the new combination several times before replacing the screw on the lock housing and closing the door.
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Use the master key on the lock if your lock model has one to get the lock open. If the key isn't working and the combination won't open the lock either, you likely need professional service. Once you have the door open, reset the lock combination using the method in step 1. The only difference is you enter the old combination into the lock before you take the screw out of the lock housing with the Allen wrench.
Use a strong magnet to apply a magnetic field to the left side of the lock housing while jiggling the knob or the latch. Many Simplex models as of 2010 respond to magnetic fields by opening but this should only be done on your own lock if you can't get it open other ways. Once the door is open, try to reset the code to get the lock working again because the code cannot be reset when the door is closed. Get the lock professionally serviced if it is still not working.