Ingersoll-Rand 900829, Maintenance Manual

Page: 64 / 142

Compressor Maintenance
62
3. Pulley or Rotor Spin Check
With clutch disengaged the pulley should spin
freely with no wobbling or roughness.
Figure 43: Pulley or Rotor Spin Check
4. Air Gap Check
Air gaps exceeding 0.051 in. (1.3 mm) can
prevent engagement. This condition is seen at the
end of normal clutch life as the friction surfaces
wear away, like brake pads.
Figure 44: Air Gap Check
5. Coil Resistance Check
Field coils with internal shorts can be tested by
measuring resistance across the field coil.
Resistance should fall within these values.
• 12 Volt coil resistance read between 2.8 and
4.4 ohms at room temperature
• 24 Volt coil resistance read between 14 and
18.2 ohms at room temperature
Figure 45: Coil Resistance Check
6. Pressure or Pumping Test
Compressors circulate refrigerant through the
system by creating a pressure differential, high
and low pressures. If the compressor can be
forced to produce a high pressure in excess of 350
psig (2413 kPa) it is a good compressor.
IMPORTANT: This test must be performed with
a full system charge! Confirm the system is fully
charged before proceeding.
1. Cover the condenser with sheet of card board.
The purpose is to limit heat rejection from the
system and build compressor discharge
pressure.
2. Start engine and engage clutch.
3. Compressors operating within specification
should be capable of reaching 350 psig (2413
kPa).
IMPORTANT: This test should only be run
for a short time period. Shut the system down
immediately once 350 psig (2413 kPa) is
achieved.
Figure 46: Pressure or Pumping Test