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Rev. A.1, 8/01 Page- i
APPENDIX A: TROUBLESHOOTING
PROBLEM-- Unit will not operate when trigger wire is connected to +V.
On a new installation, make sure that DC power (12 or 24 volts depending on the model) is connected to the red
and black wires with correct polarity. When this is confirmed, note that the Mortise UnLatch will never operate
unless the springlatch plunger is pushed in by the springlatch (see Section 3.3). You can be “fooled” by this feature
if you’re trying to test operate the Mortise UnLatch with the door open. To do this, use a pencil or other similar
object to lightly push in the springlatch plunger and then close the trigger wire to +V and you will see the Mortise
UnLatch plungers move.
On a service call for a unit with successful operating history, in addition to the checks mentioned above, check to
see if the door and latch have gotten into a warped situation where there is heavy pre-loading on the door. The
Mortise UnLatch’s motor may not be able to release the latch under this condition but you should be able to hear it
trying to release the latch. The Mortise UnLatch will automatically shut down its motor if it can’t release the latch
within 1.5 seconds. It will operate normally when it is re-triggered. You should be able to try operation by removing
the pre-loading by pushing the door closed with enough force to counteract the pre-loading. Note that this situation
is more likely if power supply capacity is less than 2 or 4 Amps (see Section 3.1). Corrections for this type of
warped door situation is to have the door serviced and possibly increase the capacity of the power supply.
If the unit still will not function, note that it does have an internal microprocessor that could have gotten into a crash
condition. This can happen some times if the unit is under-powered (see Section 3.1) and has consequently stalled
(the motor is not receiving enough power to operate the latch). While the motor is in the process of stalling, voltage
to the processor will sharply drop and this can crash the microprocessor. A crash can also occur as a random
event but this is unusual. The recovery technique is to de-power the unit, and then re-power it with the red and
orange wires already connected (both then connect to +V). This re-initializes the firmware. Naturally, once this
operation has been performed, return the unit to standard wiring (orange only connects to +V to trigger the unit.)
Finally, the unit could have experienced motor failure or other internal electronic failure. It is repairable by the
factory.
PROBLEM -- Unit will occasionally not operate.
Generally, this comes from too much door pre-loading possibly coupled with a low capacity power source. When
the Mortise UnLatch can’t generate enough torque to release the latch, it automatically shuts down but then
operates the next time it is triggered. See the previous paragraph.
PROBLEM -- Latch does not re-secure when the door re-closes.
This is not a problem with the Mortise UnLatch but is rather a problem with the installation. The latch is simply not
moving into position. Make sure the door closer is properly operating to re-close the door with reasonable force.
Next, re-read Section 2.5 to make sure the Mortise UnLatch is in the correct position with respect to the door stop.
PROBLEM -- Latch status sensing does not function.
The latch status output contacts (see Section 3.3) will change state when the springlatch plunger is pushed in. To
check this, therefore, push the springlatch plunger lightly in with a pencil or other similar object. Make sure the unit
is receiving power when you make this check or the output contacts will not switch. If they still do not switch, the
unit will need to be returned to the factory for repair.
PATENTS
The Mortise UnLatch is covered under U.S. patents #5,474,342 and #6,022,056 with other US
and international patents pending.