Viking DDBF036LSS, Service Manual

Page: 25 / 50

Component Testing
©2007 Viking Preferred Service 25
Component Description Test Procedures
Drier (cont.) 7. Apply heat trap paste on post condenser tubes
to protect grommets from high heat.
8. Unbraze remaining part of drier. Remove drier
from system.
9. Discard drier in safe place. Do not leave drier
with customer. If refrigerator is under warranty,
old drier must accompany warranty claim.
WARNING
To avoid death or severe personal injury, cut
drier at correct location. Cutting drier at
incorrect location will allow desiccant beads to
scatter. If spilled, completely clean area of
beads.
Evaporator
defrost heater Activated when defrost thermostat,
defrost timer, and freezer control
complete circuit through heater. Check resistance across heater.
To check defrost system :
1. Thermocouple defrost thermostat and plug
refrigerator into wattmeter.
2. Turn into defrost mode. Wattmeter should read
specified watts (according to Technical Data
Sheet).
3. When defrost thermostat reaches specified
temperature ±5°F (see Technical Data Sheet),
thermostat should interrupt power to heater.
Thermostat Thermostat is in a series circuit with
terminal 2 of defrost timer, and defrost
heater. Circuit complete if evaporator fan
motor operates when cold.
Controls the circuit from freezer
thermostat through defrost terminator to
defrost heater. Opens and breaks circuit
when thermostat senses preset high
temperature.
Test continuity across terminals.
With power off and evaporator coil below freezing,
thermostat should show continuity when checked
with ohmmeter. See Heater, evaporator (defrost)
section for additional tests.
After defrost thermostat opens, thermostat remains
open until end of defrost cycle and refrigerator starts
cooling again. Defrost thermostat senses a preset
low temperature and resets (closes).
Evaporator Inner volume of evaporator allows liquid
refrigerant discharged from capillary to
expand into refrigerant gas.
Expansion cools evaporator tube and fin
temperature to approximately -20°F
transferring heat from freezer section to
refrigerant.
Passing through suction line to
compressor, the refrigerant picks up
superheat (a relationship between
pressure and temperature that assures
complete vaporization of liquid
refrigerant) as the result of capillary tube
soldered to suction line.
Refrigerant gas is pulled through suction
line by compressor, completing
refrigeration cycle.
Test for leaks in evaporator with electronic leak
detector or with soap solution. Compressor oil is
circulated with refrigerant; check for oil when
checking for leaks.
For minute leaks
1. Separate evaporator from rest of refrigeration
system and pressurize evaporator up to a
maximum of 140 PSI with a refrigerant and dry
nitrogen combination.
2. Recheck for leaks.
WARNING
To avoid severe personal injury or death from
sudden eruptions of high pressure gases,
observe the following:
•
Protect against a sudden eruption if high
pressures are required for leak checking.
•
Do not use high pressure compressed
gases in refrigeration systems without a
reliable pressure regulator and pressure
relief valve in the lines.