Skope B2412, Service Manual

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57
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Troubleshooting
Service Manual
Compressor will not start:
hums but trips on overload
protector.
• Improperly wired. • Check wiring against diagram (see
page 22).
• Low voltage to unit. • Determine reason and correct.
• Start capacitor defective on
CSIR or CSR motor.
• Determine reason and replace.
• Run capacitor defective on
PSC motor.
• Determine reason and replace.
• Relay failing to close. • Determine reason and correct.
Replace if necessary.
• Compressor motor has a
winding open or shorted.
• Check resistance values. Replace
compressor if necessary.
• Internal mechanical trouble in
compressor.
• Replace compressor.
Compressor starts, but does
not switch off.
• Improperly wired. • Check wiring against diagram (see
page 22).
• Low voltage to unit. • Determine reason and correct.
• Relay failing to open, due to
welded contacts or relay
incorrectly mounted.
• Determine reason and correct.
Replace if necessary.
• Run capacitor defective on
CSR motor.
• Determine reason and replace.
• Excessively high discharge
pressure.
• Clean condenser. Check power input
Watts. Possible overcharge,
insufficient condenser cooling, or non-
condensible gasses.
• Compressor motor has
winding open or shorted.
Check continuity and
resistance.
• Replace compressor if faulty.
• Internal mechanical trouble in
compressor (tight). May be
lubrication.
• Replace compressor.
Compressor starts and runs,
but short cycles on overload
protector (relay may chatter on
RSIR, CSIR and CSR motors).
• Additional current passing
through overload protector.
• Check wiring diagram. Check for
added fan motors etc., connected to
wrong side of protector.
• Low voltage to unit. • Determine reason and correct.
• Overload protector defective. • Check current, replace protector.
• Run capacitor defective on
CSR motor.
• Determine reason and replace.
• Excessive discharge
pressure.
• Check condenser, check ventilation,
check for restrictions in refrigeration
system.
• Suction pressure too high. • Check for possibility of misapplication.
• Compressor too hot -
insufficient suction gas
cooling.
• Check refrigerant charge (fix leak),
add if necessary. Check return vapour
temperature and suction superheat.
• Compressor motor has a
winding shorted.
• Replace compressor.
Unit runs OK, but short cycles. • Overload protector. • See section above.
• Electronic controller not
operating correctly
• Diagnose fault with controller and
service as necessary (see page 10).
• Incorrect refrigerant charge. • Adjust refrigerant charge.
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Problem Possible Cause Suggestions