Compressor - Small Hvac System; Removal - When The Compressor Is Operational; Removal - When The Compressor Is Inoperable - PREVOST H3-41 Maintenance Manual

divided into suction and discharge areas. The
upper central section of the cylinder is the
suction side and it should be relatively cool to
the touch, as opposed to the hot discharge area
which is the lower perimeter area of the cylinder
head. If a valve plate or head gasket is blown, or
a compressor unloader is stuck open, partially
compressed refrigerant vapor will be circulated
between the suction and discharge sides of the
head. The affected cylinder head will then have
a relatively even temperature across its surface
and be neither as hot as the normal discharge
temperature nor as cool as the normal suction
temperature.
Blown Head Gaskets
Symptom:
• Loss of unit capacity at low temperature.
• Even cylinder head temperature.
Cause:
• Improperly torqued cylinder head bolts.
• Improperly positioned gasket at assembly.
• Warped cylinder head.
• Severe liquid refrigerant floodback.
Blown Valve Plate Gaskets
Symptom:
• Loss of unit capacity at medium and low
temperatures.
• Very hot cylinder head surface.
• Higher than normal suction pressure.
Cause:
• Improperly torqued cylinder head bolts.
• Severe liquid refrigerant floodback.
• Oil slugging caused by an overcharge of oil
or flood starts.
• Discharge valves not seated properly (liquid
drainback during shutdown).
Broken Suction Valves
Symptom:
• Loss of unit capacity at all temperatures.
• Compressor unable to pull extremely low
vacuum with suction
frontseated.
Cause:
SECTION 22: HEATING AND AIR CONDITIONING
shutoff valve
PA1621 Maintenance Manual All Series | Revised February 2019
• Repeated liquid refrigerant floodback.
• Flooded starts.
• Overcharge of oil.
• Discharge valves not seated properly (liquid
drainback during shutdown).
• Expansion valve not controlling properly.
Unloader Valve Stuck Open
Symptom:
• Loss of unit capacity at all temperatures.
• Higher than normal suction pressure.
• Even cylinder head temperature.
Cause:
• Unloader body stem bent.
• Foreign material binding unloader piston or
plunger.
4.2 COMPRESSOR – SMALL HVAC
SYSTEM
Read the cautionary information in the small
compressor service manual: Sanden SD/SD7
Compressor Service Manual, found on your
Technical Publications USB flash drive.
4.2.1 Removal - When The Compressor Is
Operational
Perform the "OIL RETURN OPERATION" (Refer
to paragraph 7.9).
NOTE
Belts specifications may vary. For proper belt
selection, always consult your vehicle Coach
Final Record.
4.2.2 Removal - When The Compressor Is
Inoperable
• Perform the "Refrigerant Recovery" operation
(paragraph7.5).
• Remove any tension on the belts
Slacken bolts fixing small compressor.
(FIGURE 37 and Figure 38)
• Remove the compressor.
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