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PROBLEM
"MP / HPCO" FAULT
COMPRESSOR(S) WON'T
START
LACK OF COOLING EFFECT
YORK INTERNATIONAL
CAUSE
1. Compressor internal motor
protector (MP) open.
2. External overload tripped.
3. HPCO switch open
4. Defective HPCO switch
5. Defective CR relay
1. Demand not great enough.
2. Defective discharge air temp.
sensor.
3. Contactor/Overload failure
4. Compressor failure
1. Dirty evaporator surface.
Low suction pressure will
be observed.
2. Improper CFM through the
evaporator.
3. Low refrigerant charge.
Low suction pressure will
be observed.
FORM 150.63-NM2
SOLUTION
1. Verify refrigerant charge is
not low. Verify superheat
setting of °10 - 15°F (5.6° -
8.3°C). Verify correct com-
pressor rotation. Verify
compressor is not over
loaded.
2. Determine cause and reset.
3. See "High Press. Disch."
Fault
4. Replace HPCO switch
5. Replace relay
1. No problem. Consult
"Installation" Manual to aid
in understanding compres-
sor operation and capacity
control.
2. Compare the display with a
thermometer. Should be
within +/- 2 degrees. Refer
to Service section for Dis-
charge Air temp./voltage tbl.
3. Replace defective part.
4. Diagnose cause of failure
and replace.
1. Contact the local YORK
service representative.
2. Verify nominal 400 CFM/ton
airflow through evaporator
3. Check subcooling and add
charge as needed.
4
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