Use a known-good machine. Have students physically locate and touch every component before moving to the next. Students should be able to find each part on any Bobcat variant.
The heart of the AC system. Belt-driven pump that compresses low-pressure refrigerant vapor into high-pressure vapor. Includes clutch, pulley, and Schrader service ports.
Heat exchanger that dumps heat from refrigerant to ambient air. With the cooling package and is often dirty.
Cold heat exchanger inside HVAC box. Absorbs heat from cab air. Includes freeze protection and drain system for condensate removal. Often plugged with debris and requires cleaning.
Stores liquid refrigerant, filters debris, and removes moisture with desiccant. Includes 535 psi pressure relief valve. Must be replaced when system is opened.
TXV (Thermal Expansion Valve) or orifice tube that meters refrigerant flow. Creates pressure drop that makes evaporator cold. Critical for proper system operation.
High-side pressure switch cuts out below 28 psi and above 384 psi. Prevents compressor operation under unsafe pressure conditions. Can be bypassed for testing with proper procedures.
AC switch, clutch, EDT (Electronic De-icing Thermostat), MCC integration. Voltage-drop testing critical for AC switch diagnosis.
Fresh air and recirculating cab filters. Restricted airflow mimics low charge symptoms. Critical for proper evaporator performance and freeze prevention.
Heater control valve and temperature blending system. Hot coolant bypass can cause warm duct complaints even when AC is working properly.
Components work as an integrated system. A failure in one component often affects others. For example: a restricted condenser raises high-side pressure, which can trigger the pressure switch and prevent compressor engagement. Understanding these relationships is key to accurate diagnosis.
Bobcat AC systems vary by model series:
- R-Series: Low-side service port accessible without raising cab, different condenser mounting
- S-Series/T-Series: Traditional port locations, different HVAC box configurations
- Compact Models: Smaller condensers, different compressor mounting arrangements