Voltage Checks - L.B. White Pilot Light Ignition Installation And Service Manual

Procedure
Testing for voltage at any of the components is a relatively
easy procedure. The following illustrates how to check
voltage at some of the components used in the heater.
Electrical S S hock H H azard
Troubleshooting may require the heater to be
connected to its electrical supply.
Do not directly
connections when checking voltage. Use only the
insulated probes of the voltage tester.
Failure to follow this warning may result in
electrical shock leading to personal injury.
First, set the function selector switch of the tester to "AC"
(alternating current). Check for voltage at either the ignition
module or the individual component. To test, place one of
your tester probes at the "hot" power supply terminal of the
component being tested and the other probe to a grounded
portion of the heater's cabinet. (Normally, a sheet metal
screw on the cabinet will serve this purpose.) Or, place your
probes across the terminals of component being tested. The
following are some examples showing both procedures:
Checking f f or v v oltage s s upply t t o m m otor.
Apply a tester probe to the end of the black motor wire and
the other probe to ground. When the thermostat calls for
heat, you will see approximately 120 volts readout on the
meter display. This verifies the thermostat is supplying
voltage and the wiring between the thermostat and the
motor is in good condition.
August 1999
Warning
touch exposed terminal
Motor
Wire
Checking f f or v v oltage s s upply t t o h h igh l l imit s s witch.
Apply the probe to the power input side of the limit switch
and the other to ground. Voltage will appear after the air
proving switch makes.
Checking f f or v v oltage s s upply t t o g g as c c ontrol v v alve
from t t he h h igh-l l imit s s witch.
Apply one probe to female terminal at end of gas control
valve wire and the other to ground. You will see voltage
appear, proving the air proving switch, high-limit switch, and
respective wires are in order.

Voltage Checks

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