DANA SPICER PACCAR 220ev, Troubleshooting Manual, Page: 522 / 761

522
Troubleshooting
HVAC System
The Heating, Ventilation and Air Conditioning
(HVAC) system provides heating, cooling, and
ventilation to the driver cab.
Component descriptions
Air Conditioning System
The air conditioning system consists of a standard
refrigeration circuit which uses a compressor,
condenser, expansion valve, and evaporator to
remove excess heat from the cab and reject it to the
surrounding atmosphere. The working fluid is R-
134a refrigerant.
The only parts of the air conditioning system which
are supplied by Dana are the A/C compressor and
the condenser fans. The remaining components are
outside the scope of this troubleshooting guide and
are presented here only to aid in understanding how
the system operates.
Condenser and Evaporator
The evaporator and condenser are forced-air heat
exchangers. The evaporator transfers heat from the
cab to the refrigerant, thereby cooling the cab. In the
process, the refrigerant undergoes a phase change
from liquid to vapor. Conversely, the condenser
transfers heat from the refrigerant to the surrounding
atmosphere as the refrigerant undergoes a phase
change from vapor to liquid. These components are
not supplied by Dana and are outside the scope of
this troubleshooting guide.
Expansion Valve
The expansion valve is between the condenser and
evaporator. It cools the refrigerant by causing it to
undergo a sudden decrease in pressure. It is not
supplied by Dana and is outside the scope of this
troubleshooting guide.
A/C Compressor
The A/C compressor is between the evaporator and
condenser. Its function is to compress and superheat
the refrigerant, which is in vapor phase, before it
enters the condenser. It is a variable-speed, screw-
type compressor. It is powered by high voltage and
communicates via the CAN network.
Condenser Fans
The two condenser fans circulate forced air through
the condenser to carry away the waste heat. The
same fans are also used by the cooling system to
circulate air through the radiator.
Blower
The blower circulates air through both the evaporator
and the heating system heat exchanger and into the
cab. The same blower is used for heating and
cooling. It is not supplied by Dana and is outside the
scope of this troubleshooting guide.
Heating System
The heating system uses a hot water circuit to
deliver heat to the cab. The heating circuit consists
of a reservoir, pump, heater, and a forced-air heat
exchanger which delivers hot air to the cab. The
working fluid is a 50/50 water and ethylene glycol
mix.
The heat exchanger is not supplied by Dana and is
outside the scope of this troubleshooting guide.
Cabin heater
The heater uses electric heating elements to heat
the water in the heating circuit. It is powered by high
voltage and communicates through the CAN/LIN.
Heater Pump
The heater pump circulates the hot water through
the heating circuit. It is powered by 12V low voltage
and is controlled by the VCU through a hardwired LV
connection.
CAN/LIN
The CAN/LIN enables the heater, which uses a
Local Interconnect Network (LIN) interface, to
communicate with the CAN network. It is powered by
12V low voltage.