Switches; Heating Elements; Thermostats; Diode Check - GB Instruments GDT-190A Manual Del Propietário

7.4 Switches

Cut off the power source to the switch. If necessary, remove
the switch. Turn the switch to the ON position and touch the
test leads to the switches terminals (see fig. 11). If the switch
is good, the display should read -0- ohms. If the display
doesn't change at all, replace the switch. On other than two-
way SPST (single pole, single throw) switches such as three-
way light switches or double pole double throw (ON-OFF-ON)
switches, in each ON position you will need to alternate the
test leads between the switches terminals to determine which
two terminals control that ON position.

7.5 Heating Elements

Household appliances such as coffee makers and water
heaters contain heating elements which may require
troubleshooting. When making continuity checks on heating
elements, disconnect the element(s) from the circuit(s) that
supply it/them. Touch the test leads, one on each end of the
element and observe the display. The reading should indicate
low ohms. If the display doesn't change, the heating element
may be broken. If the element(s) show that continuity exists,
test for continuity of the circuit(s) that feed the element(s).

7.6 Thermostats

Make sure the thermostat control is in the OFF position.
Remove the thermostat cover. Touch the test leads to the contact
points on the thermostat. The display should read -0- ohms. If not,
either one of the contacts may be loose or broken.
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Figure 11

8. Diode Check

Diodes should be tested with both forward and reverse
voltages applied:
1) Plug the red (+) test lead into the (+) input jack, and the
black (-) test lead into the COM input jack. Set the
function/range switch to the diode test setting.
2) Touch the test leads to the diode, one lead on the anode
and the other on the cathode. The indication of a diode in
good condition is a low resistance reading when the red
lead (+) is on the anode and the black (-) lead is on the
cathode (see fig. 11). When the test leads are reversed
(reverse voltage is being applied), a high resistance
reading should be displayed.
NOTE: A low resistance in both directions indicates a
shorted diode; a high resistance in both directions indicates an
open diode. In either case the diode is defective and should
be replaced.

9. Battery Replacement

1) Remove the screws in the back cover of the tester and
carefully separate the back cover from the front.
2) Note the polarity of the battery terminals when removing it
from its connector and replace.
3) Carefully replace the back cover and tighten the screws.
Do not overtighten the screws as this may strip the threads
in the tester housing.
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