Refrigeration System
Refrigeration SystemA/C Components:
Air conditioning
In an effort to lessen the impact of the motor vehicle on the environment, the 1993 model year Sedan Range vehicles use an HFC refrigerant air conditioning system. HFC [hydro-fluorocarbon) refrigerants are more compatible with the environment than the former CFC [chlorofluorocarbon) refrigerants.
HFC Refrigerant
The use of HFC refrigerant required a redesigned air conditioning system plus revised service procedures with equipment especially designed for charging, recovery and servicing.
PAG Compressor oil
HFC refrigerant requires the use of PAG [polyalkaline glycol) synthetic lubricating oil. Because of the extreme hygroscopic [moisture absorbing) nature of PAG oil, containers of PAG oil must not be left uncapped.
Refrigerant and lubricant specifications:
^ Refrigerant type HFC 134a
^ Refrigerant charge [weight) 2.5 pounds
^ Lubricating oil type PAG type SP2
^ Compressor initial oil charge 4.5 fluid ounces
Servicing with PAG oil
The following precautions must be observed during servicing to ensure that PAG oil in the air conditioning system does not become contaminated.
^ During system replenishing, exposure of lubricating oil to the atmosphere must be kept to an absolute minimum.
^ Recovered PAG oil must not be reused. An equivalent amount of fresh oil must be injected into the system before recharging. Use a PAG oil injection device.
Compressor
An HFC-compatible Sanden SD 7H 15 compressor (a modified 709 compressor) is used to compress and circulate the refrigerant.
Condenser And Receiver/Drier:
Condenser and receiver/dryer
The condenser is constructed of extruded aluminum tubes with corrugated fins. The HFC-compatible receiver/dryer is mounted horizontally on the top of the condenser. The receiver/dryer sight glass has been eliminated because the combination of HFC refrigerant and PAG lubricating oil gives a milky appearance, making observation unreliable.
Expansion Valve:
Evaporator and expansion valve
The evaporator is constructed entirely from aluminum. The expansion valve uses clamp plate connections on both sides of the valve. Some of the expansion valve internal parts are made from stainless steel to be compatible with PAG oil.
Quick Connect Couplers:
Refrigerant lines and couplings
The refrigerant lines are constructed from aluminum pipes and HFC-compatible flexible hose. Couplings at the compressor and at the condenser inlet are quick-connect fittings. The couplings are disconnected by fully unscrewing the connection [after the system has been depressurized). Connection is made by pushing the pipe into the connector after it has been assembled and fully tightened.
Pressure Switches:
Refrigerant pressure switches
Two pressure switches (one triple, one single) are located in the high pressure [liquid refrigerant) line between the compressor and the expansion valve.
Triple switch
The triple switch has three functions: compressor cut-out if the high side pressure is high, compressor cut-out if the high side pressure is low and auxiliary cooling fans parallel operation (high speed). The three functions are accomplished as follows:
^ Compressor on - refrigerant pressure between 2 and 27 bar [29-392 psi)
^ Parallel fans on - refrigerant pressure greater than 20 bar [290 psi).
Single switch
The single switch operates the auxiliary cooling fans in series [low speed).
^ Series fans on - refrigerant pressure greater than 15 bar (218 psi).
Charge Valve:
Refrigerant charge valves
The low and high side charge valves are designed to accept only HFC-type connection, preventing incorrect system charging.