Description

Front & Rear Heat & A/C (C69):

Front & Rear Heat & A/C (Recreational Vehicle):

Front Heat & A/C (C60):

The Cycling Clutch Orifice Tube (CCOT) refrigerant system is designed to cycle the compressor on and off to maintain desired cooling and prevent evaporator freeze-up. Passenger compartment comfort is maintained by the temperature selector on the controller.

Control of the refrigeration cycle (on and off operation of the compressor) is done with a switch that senses low side pressure as an indicator of evaporator pressure. The cycling pressure switch is the freeze protection device in the system and senses refrigerant pressure on the suction side of the system. This switch is located on the accumulator. During air temperatures of 10°C (50°F), the equalized pressures within the charged air conditioning system close the contacts of the pressure switch.

When an air conditioning mode is selected, electrical energy is supplied to the compressor clutch coil. As the compressor reduces the evaporator pressure to approximately 159 kPa (23 psi), the pressure switch opens, de-energizing the compressor clutch. As the system equalizes and the pressure reaches approximately 315 kPa (46 psi), the pressure switch contacts close, re-energizing the clutch coil. This cycling continues and attempts to maintain evaporator discharge air temperature at approximately 1°C (33°F).

Because of this cycling, some slight increases and decreases of engine speed/power may be noticed under certain conditions. This is normal as the system is designed to cycle to maintain desired cooling and prevent evaporator freeze-up.

Additional compressor protection results from the operating characteristics of the low-side cycling pressure system. If a massive discharge occurs in the low side of the system, or the orifice tube becomes plugged, low-side pressures could be insufficient to close the contacts of the pressure switch. In the event of a low charge, insufficient cooling accompanied by rapid compressor clutch cycling will be noticed at high air temperatures.

When the engine is turned "OFF" after the air conditioning system has been operating, the refrigerant in the system flows from the high-pressure side of the expansion (orifice) tube to the low-pressure side until the pressure is equalized. This may be detected as a hissing sound for 30 to 60 seconds and is a normal condition. This sound actually occurs during operation as well, but is not audible with the engine running.
The heating and air conditioning systems that are available for this vehicle are described below and in the illustrations.

^ C36 Rear Auxiliary Heat Only
^ C42 Front Base Heat
^ C60 Front Heat and A/C
^ C69 Rear Auxiliary A/C and Heat
^ C42 & C36 Front and Rear Heat
^ C60 & C36 Front Heat A/C and Rear Heat
^ C60 & C69 Front and Rear A/C and Heat

Rear A/C System (C69)

The rear A/C system operates with the front system. It does not operate independently. However, control of the rear blower motor speed is possible when the front system is off. Rear air circulation without the refrigerant function is possible by operating the rear blower control switch.

These units operate on inside (recirculated) air. Air enters the unit and passes through the evaporator core into the passenger compartment through the air distributor duct. The front system controls the rear system. A three-speed blower switch controls the rear overhead system.