Download With a basic understanding of schematics, a schematic can be used

With a basic understanding of schematics, a schematic can be used to troubleshoot why an operator is
not working. The most important tool for a field technician is a working and reliable voltage multi-meter.
The meter should be able to read AC and DC voltages, and continuity. Continuity checks if a circuit is
complete or not. Remember, for an electrical device to activate, the electrical circuit or path to it must
be complete. Again, we will use diagram 10118-1 to illustrate, assuming a 120VAC operator. This
diagram uses AC voltage, so the meter should be set to VAC or V~. When using a meter, polarity does
not matter. Also, do not check to ground, it will not provide an accurate reading (DC voltage is checked
to ground).
The first step is to check if the operator is getting properly powered. Place one lead at L1, the other at
L2:
The meter should read the operator’s rated line voltage, +/- 10%. If there is no voltage, check the
operator’s breaker.
Mechanical operators use a centrifugal start switch in the motor. Voltage to the IR relay is feed through
this start switch:
When the unit is powered and the IR relay is energized, the contacts on it close allowing the open and
close buttons to work:
If the operator has power, but the open or close buttons do not work, check that the IR relay is getting
line voltage at the two black wires on the coil of the relay. A common problem with mechanical motors
is that the start switch can stick open, cutting off voltage to the IR relay. A typical symptom for a stuck
start switch is the unit will not respond to open or close commands. When pressing open, the R1 relay
will click; there will be no response with the close button.
Another possible issue is that the transformer is not supplying 24VAC control voltage. With the meter,
test the yellow and brown wire leads on the secondary side of the transformer; there should be 24VAC
(Figure 1). If there is no voltage, test the black and white wires to the primary side of the transformer,
there should be the same line voltage as seen at L1 and L2 (Figure 2).
Figure 1:
Figure 2:
Let us run through the steps for checking a circuit. For example, the door is closed and will not open. The
R1 relay clicks but the open contactor does not engage.
The first step is to remove all external accessory wiring, including the three button control station.
Ensure the factory jumper wire is in place at terminals 4 and 5, and then install a second jumper wire
between terminals 3 and 4. Take another jumper wire and short terminals 1 to 3 for a second and see if
the door opens. If it does, the push buttons or the wiring is the issue.
If it does not open, test for voltage at terminal 5 and the wire nut. This test verifies the transformer is
good and the interlock (if equipped) is working.
If there is voltage, check terminal 1 to 3. The open part of the open control circuit, it should have 24VAC.
If there is no voltage, the open button will not work. Test the open limit switch next. Read each orange
wire on the limit to terminal 3; each should show 24VAC. Another way to test the limit switch is to
remove the orange wires from it and stick them together, this bypasses the switch.
If one orange wire has voltage, but the other does not, replace the limit switch. If both have voltage,
check the contactor. Read A2 to terminal 3, then A1 to terminal 3; each should have 24VAC.
If A2 has voltage, but A1 does not, the coil of the contactor is damaged, replace the contactor. This is
very rare.
Next, check terminal 3 to the orange and yellow wires on the IR relay.
If there is no voltage at the yellow wire and terminal 3, trace back to 13NO on the open contactor,
making sure the wires are connected. If the yellow wire has voltage but the orange wire does not, check
that the wires are on the C (common) and NO (normally open) contacts. You can also bypass the IR relay
but touching the orange and yellow wires together. If they are on the correct contacts, and the relay has
line voltage to the coil, replace the relay.
Similar steps can be taken to check the close circuit. The close circuit also has an additional set of
contacts from the R1 relay. These contacts are NC. To test the R1 relay, check terminal 3 to each of the
purple wires on the relay.
If one purple wire has voltage, but the other does not, double check that all external accessories are
removed so an accessory is not giving an open command. Remove one of the red wires from the R1
relay, and then check each purple wire again. If only one still has voltage, make sure they are on the C
and NC contacts. If they are, replace the relay.