General Maintenance and Troubleshooting
3-16 SM 6495, Rev. 7, December 2008
3.3.2. Testing and Troubleshooting the Power Down Module for 24-Volt Systems
The following procedure describes the steps taken to test the power down module (Figure 5-12 or
Figure 5-13, Item 275).
1. With arm in the clear position, place voltmeter on terminals 6B(-) and 3C(+). The meter should
read approximately 0 volts (refer to
Figure 2-4 for terminal locations).
2. With arm descending, place voltmeter on 6B(-) and 3C(+). The meter should read 24 VDC.
3. There will also be 24 VDC between 6B(-) and 3A(+) until the arm reaches the 45° point (halfway
down or at point No. 3 contact opens). The meter should read 0 volts on 3A at this point.
If this test resulted in incorrect readings, check the following:
1. Check the No. 3 contact for proper adjustment.
2. Check the limit resistor to ensure it is not open.
3. Check for proper wiring (refer to Figure 2-4).
4. If no problems are found with items one through three above, then replace the Power Down Relay.
3.3.3. Verification of Maintenance Switch Operation
Note that the function of the maintenance switch is to drive the mechanism to the down position
without the arm installed. The following procedure is recommended instead of a functional test.
1. Loosen the gold nut on Terminal 5B and reconnect power to the gate mechanism (refer to
Figure
3-2 for terminal location).
2. Connect a voltage meter to the gate mechanism, with the positive meter lead on motor Terminal T6
and the negative meter lead on Terminal T7.
3. With the arm in the up position, operate the toggle switch on the maintenance switch to the
MAINTENANCE position and momentarily push the PUSH AND HOLD button. The arm should
power down, giving a positive reading on the voltage meter. The positive meter reading verifies
proper wiring terminations.
4. Return the toggle switch to the NORMAL position and power arm to up position by resecuring the
gold nut on Terminal 5B.
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