AIR CONDITIONING SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
REFRIGERANT SYSTEM CHARGE - CONTINUED
Relationship Between Temperature and Pressure (R-134a Refrigerant) - Continued
Table 3. Relationship Between Temperature and Pressure (R-134a Refrigerant) - Continued.
TEMPERATURE °F (°C)
PRESSURE PSI(1) (KPA)
186.3 psi (1,285 kPa)
189.1 psi (1,304 kPa)
191.9 psi (1,323 kPa)
194.7 psi (1,342 kPa)
197.6 psi (1,362 kPa)
200.5 psi (1,382 kPa)
203.4 psi (1,402 kPa)
206.3 psi (1,422 kPa)
209.3 psi (1,443 kPa)
(1) All pressures in this table are gage pressures.
REFRIGERANT COMPRESSOR TEST
N OT E
· If compressor fails any one of the steps, AC system should be diagnosed in order to find root cause of fail-
ure. Root cause of failure should be repaired. If compressor is considered to be "good", additional assis-
tance with diagnosis of AC system can be found by contacting your Caterpillar dealer.
· Identifying compressors that function is the purpose of this test. Compressors that function should be iden-
tified before compressors are removed from a machine. Compressors that function should produce both
high pressure and low pressure.
Check Air Filters. If complaint of customer is poor cooling of cab, past experience has shown plugged air filters can
often be cause. Most AC systems have return air filters and fresh air filters. Be sure to check both return air filters and
Test Voltage. While engine is running and AC is switched ON, check voltage at compressor. Voltage at compressor
should be a minimum 23V. Routinely used electrical loads should be turned ON. For example, a lighting system which
is added by customer could cause available voltage to decrease below minimum specification.
Test Resistance. Measure resistance of clutch coil at compressor connector. Measured resistance should be within -1.3
to +5.5 of 17.6 + 0.6 Ohms. Resistance range listed compensates for effect of temperature on clutch coil.
Check Belt Tension. Refer to WP 0046 00.