When you are troubleshooting and doing repair
work, TREAT ELECTRICITY WITH
RESPECT. Working with electricity is
hazardous, and you must take every precaution
to avoid electrical shocks, burns, and
electrocution. Regard all circuits as live until
you have opened the switches or have made
voltage tests and know that the circuit is dead.
Lock and tag all switches in the OPEN position
to keep other personnel from tampering with
them and creating a safety hazardous condition.
Remove protective devices, such as fuses, from
their holders. REMEMBER, YOU WILL BE
WORKING ON THAT CIRCUIT.
Controls and Elements
Controls and elements on appliances or equipment
will most likely be your biggest problem. Check
switches and controls with an ohmmeter for the making
or breaking of contacts.
If the switch is ON, the
ohmmeter should read "0." The operation of a switch
can be checked with a voltmeter. Check for voltage
input and output.
New switches are usually inexpensive, so repairing
an old one is not economical. The contacts may be
reformed as a temporary measure to ensure a positive
contact for completing the circuit. Lubricating the
contacts and spring mechanics with a nonoxide grease
reactivates the switch operation.
Repair of the bimetallic blade control switch is
limited to an adjustment in the temperature setting of the
control to agree with the temperature recorded in the
appliance or equipment being tested. Temperature of
equipment should be tested by a reliable temperature
tester or a good thermometer.
Repair of the helix control is limited to adjusting the
temperature setting of the control to agree with the
temperature recorded in the appliance or equipment
being tested. If the control cannot be adjusted, the
complete control assembly must be replaced.
If a timer fails to operate, use the following
procedures to locate the trouble:
Test the electrical circuit for a blown fuse.
Check for friction between the hands of the timer
and timer crystal.
Check all wire connections.
To repair an inoperative electric timer, perform the
Replace the blown fuse with a fuse of the proper
Replace the complete rotor if the rotor is
Replace the complete coil assembly if the field
coil is burned out.
Repair the timer switch assembly by cleaning
contacts or reforming the contact arm to ensure
positive contact. If the contact shows excessive
wear, replace the switch assembly.
Adjust the hands of the timer if they are binding.
Check all connections at the back of the timer for
positive contact to ensure a complete circuit.
Elements can be checked using a -voltmeter or
ohmmeter. If a voltmeter is being used remove one
wire from the element and check for voltage between
the empty terminal and ground. A voltage reading
indicates a good element, and no voltage indicates an
open or defective element.
If an ohmmeter is used, first ensure that the power is
disconnected. Remove both conductors to prevent a
false reading. Connect the two leads of the ohmmeter to
the two terminals of the element. A reading of zero
indicates a good element. A reading of infinity symbol
indicates an open element.
PORTABLE ELECTRIC TOOL
If you have ever had an encounter with an
ungrounded electric drill while working in the rain, you
have a feel for the importance of tool testing. You will
also have gained a healthy respect for the person who
tests tools at the battalion central tool room (CTR) or the
Public Works Department (PWD) when he or she fmds
and corrects the problem with portable electric power
The tool tester shown in figure 7-16 is an example
of a tool tester that personnel from CTR or PWD might
The tool tester consists of a transformer, sensing
relays, indicator lights, an audible warning buzzer, and
leads suitable for tool or appliance connections.