MacDon 9250 Operator's Manual page 114

Cab Air System
COMPRESSOR PROTECTION
The compressor is protected from excessively low
suction and high discharge pressures by two
switches:
• Low suction pressure switch is located at the
outlet of the evaporator (under seat in cab). It
will close when the pressure drops below 4±2
psi and re-open when pressure rises above
20±5 psi.
• High discharge pressure switch is located on
the receiver drier (rear of tractor, behind right
side panel). It will close if pressure exceeds
325±10 psi and re-open when pressure drops
below 250±30 psi.
LOW SIDE
PRESSURE
VERY LOW
LOW
LOW
HIGH
HIGH
HIGH
NORMAL
LOW
NOTE: Service ports are located on suction and discharge hoses at compressor.
Form # 46584
MAINTENANCE/SERVICE
HIGH SIDE
PRESSURE
VERY LOW Lack of R134a
LOW Loss of R134a
Restriction between condenser and drier
LOW OR Restriction between drier and expansion valve
NORMAL Expansion valve plugged
Expansion valve stuck closed
Inoperative blower motor
Plugged filter or evaporator core
Moisture in system
Defective temperature control switch
Restriction at expansion valve
Restriction in evaporator
Restriction between evaporator and compressor suction
LOW Compressor belt slipping
Magnetic clutch slipping
Compressor internal failure
HIGH Condenser malfunction
Condenser coil plugged
Expansion valve stuck open
Restriction between compressor and condenser
Restriction inside condenser
Overcharge of refrigerant
Air in system
NORMAL Expansion valve stuck open
HIGH Restriction between compressor and condenser
Restriction inside condenser
Overcharge of refrigerant
HIGH Restriction between compressor and condenser
Restriction inside condenser
112
To prevent damage to the compressor, if the air
conditioning system is shut down by either switch,
locate the source of the problem and correct it
before operating the system.
REFRIGERANT OIL
Whenever the machine is first started after storage
for more than one week: Turn blower switch to
"OFF" and turn A/C temperature control switch to
maximum cooling. Start engine and operate at low
idle. Click blower switch from "OFF" to "LOW" for
one second, then back to "OFF" for 5 to 10
seconds. Repeat this cycle ten times to distribute
the oil throughout the system.
POSSIBLE
CAUSE
Issue 11/06 Web Rev_01