Thermo King 914970, Manual

Page: 72 / 186

Electronic Controls
72
Testing the TG-V Thermostat
Tools and Materials Required for Testing
1. Volt/ohm meter capable of accurately reading
1/100 volt increments.
2. Jumper Wires
3. Three Relays, Part No. 44-5847
4. One 12 Vdc Power Supply
5. Mercury Thermometer
TG-V Calibration
The TG-V thermostat is permanently calibrated,
and no attempt should be made to recalibrate it.
The thermostat module is a non-serviceable item
and repairs should not be attempted. If the
thermostat is found to be defective, replace it.
Ice-Water Bath Preparation
1. Fill an insulated container full of ice. Add
enough water to cover the top of the ice during
the test procedure.
2. Remove the sensor bulb from the unit or use a
known good sensor for testing the thermostat
module.
3. Stir the ice-water bath for one minute or until
stabilized at 32 F (0 C).
4. Monitor the ice-water bath temperature with a
mercury thermometer during testing to ensure
test accuracy.
NOTE: Before testing a questionable thermostat
module, it is a good idea to check the thermostat
sensor first.
Sensor Test
1. Visually check the bulb end, lead, and
terminal end of the sensor. Make sure that it is
not damaged.
2. Using an ohmmeter capable of reading at least
4000 ohms, check resistance between the
sensor leads.
3. Sensor resistance should be approximately
3000 to 3500 ohms. Use the following method
to give the sensor a more accurate test:
a. Cool the sensor down to 32 F (0 C) and
check the resistance—reading should be
3266 ± 3.4 ohms.
b. Warm the sensor up to 70 F (21.1 C) and
check the resistance—reading should be
3450 ± 6.9 ohms.
4. If the sensor does not meet specifications,
replace it.
5. If the sensor does meet specifications, proceed
to TG-V thermostat bench test.