Troubleshooting - Test D, Minimum Motor Speed Test; Troubleshooting - Test E, Thermal Cut-Out Of Electronic Unit; Troubleshooting - Test F, Not Cooling, Not Turning On - Norcold DC558 Service Manual

Troubleshooting, cont'd.

Troubleshooting - Test D, Minimum Motor Speed Test

1. Perform the "Diagnostic Pre-checks".
2. Remove the unit from its enclosure leaving the DC power sup-
ply connected.
3. Check that the unit is ventilated properly and condenser coil
(11) is clean and fan is operational. Max operational ambient
temperature is 131° F (55° C).
4. Check to make sure the input voltage is:
• Between 10.9 VDC and 17 VDC (12 VDC nominal input).
• Between 23.8 VDC and 31.5 VDC (24 VDC nominal input).
• Refrigerator is not overloaded with hot items or trying to
operate in high ambient conditions.
Is input voltage within specifi cation?
• Yes: Go to next step.
• No: Fix voltage level.
5. Is unit overloaded?
• Yes: Reduce load on unit.
• No: Go to next step.
6. Is fan running and the coils clean and not restricted?
• Yes: Replace cooling unit.
• No: Replace control module.
Troubleshooting - Test E, Thermal Cut-Out of
Electronic Unit
1. Perform the "Diagnostic Pre-checks".
2. Remove the unit from its enclosure leaving the DC power sup-
ply connected.
3. The control module (3) has a built in thermal protection which
stops the compressor operation if the control module circuit
board temperature is higher than 212° F (100° C). Check that
the unit is ventilated properly and condenser coil (11) is clean
and fan is operational. Max operational ambient temperature is
131° F (55° C).
4. Test unit.
Did code 5 return?
• Yes: Replace control module.
• No: Repair complete.
DC558

Troubleshooting - Test F, Not Cooling, Not Turning On

1. Perform the "Diagnostic Pre-checks".
2. Remove the unit from its enclosure leaving the DC power sup-
ply connected.
Have any wires become disconnected from their terminals?
• Yes: Reattach wire(s) and test unit. Refer to wiring sche-
matic.
• No: Go to next step.
3. Does green "ON" indicator light and or interior light come on
when unit is turned ON?
• Yes: Both come on. Go to step 6 (Polarity check).
• No: Neither come on. Go to next step.
4. Is DC fuse intact?
• No: Replace fuse. Test unit.
• Yes: Go to next step.
5. With the thermostat 6) in the OFF position, use a DVOM to
check the input voltage. Is input voltage higher than cut-in volt-
age? See "Specifi cations" section.
• Yes: Go to next step.
• No: Repair input voltage, test unit.
6. Is DC input connected correctly (Positive lead to "+" terminal
and negative lead to "-" terminal)?
• Yes: Go to next step.
• No: Correct DC input connections, test unit.
7. Verify continuity of compressor wiring harness. Remove control
module and control module base, remove compressor interface
cover, unplug the harness at each end and check for continuity.
Is the wire OK?
• Yes: Go to next step.
• No: Replace compressor wiring harness, test unit.
8. With the compressor wiring harness unplugged from the
compressor, check to ensure resistance between all three (3)
current lead-in pins on the compressor is .37 OHMS. Are the
measured values approximately the same?
• Yes: Problem is in the control module. Replace control
module.
• No: Problem is in the compressor motor. Replace cool-
ing unit.
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