WD Catalog 2018

10-3

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Table of Contents

Index

Replacing & Repairing AC Components

POWER IN

CIRCUIT BREAKER

OR FUSE

CLUTCH COIL

RELAY (OPTIONAL)

TRINARY™ OR BINARY™ SWITCH

THERMOSTAT SWITCH

PRESSURE SWITCH (NEAR CONTROL

PANEL ON AIR CONTROL SYSTEM)

CONTROL SWITCH (HEAT/AC SWITCH

OR INCLUDED IN FAN SPEED SWITCH)

CIRCUIT BREAKER OR FUSE

POWER IN (12V DC)

LOW SIDE LOW PRESSURE SWITCH (LSLP)

HIGH SIDE LOW PRESSURE SWITCH (HSLP)

HIGH SIDE HIGH PRESSURE SWITCH (HSHP)

Servicing the Compressor

Every AC system and compressor depends on refrigeration oil for lubrication

and safe operation. Whenever an AC system is opened for service, check the

compressor oil level and add clean refrigeration oil as required by manufac-

turer specs. This is especially important with a rotary compressor that has no

oil sump.

WARNING

Different lubricants are used in R-12 and R-134a sys-

tems. They must not be mixed.

Compressor Repair

Vehicle down time or travel delay can be very costly to the heavy duty rig

operator. For this reason, compressor service and repair is usually more

costly than replacement with a new or rebuilt compressor. We have

limited compressor and clutch service and repair coverage because each

compressor make (and model) requires special tools and procedures for

complete repair capability. Compressor manufacturers publish service

manuals for their products.

HVAC Control System Variations—Troubleshooting

We described Binary™ and Trinary™ switches, air operated controls (Air

Block) and CTC™ or Constant Temperature Control in

Chapter 5

. These

control devices are often specified on heavy duty vehicle HVAC systems.

Troubleshooting and servicing are explained here.

Figure 10-1

Wiring schematic for the

clutch circuit. Two or more

of these switches may be

found in a clutch circuit.