Electrical Systems - Chassis
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2 0 0 2 N E P T U N E
9 • 277
R-134a Refrigerant:
R134a is classified non-explosive, non-flammable and non-corrosive. It
has hardly any odor and is much heavier than air. R134a is ozone friendly;
however, it is not technician friendly. Proper care in handling and adequate
ventilation is a must. Under normal atmospheric pressures and temperatures
R134a evaporates so quickly it freezes anything it comes in contact with. The
open container boiling point for R134a is minus 21.7º F, which makes it an ideal
refrigerant. The tremendous amount of heat transfer which occurs when a liquid
boils, or vapors condense, forms the basic principles of all A/C systems. The
amount of heat required to raise or lower the temperature of 1 lb. of water by 1º
F equals 1 BTU (British Thermal Unit). The BTU is the standard measurement of
an air conditioner system.
Safety and Handling of 134A and Pag Oil:
• Wear eye and hand protection when working with any refrigerant system.
• Pag Oil irritates the skin. Flush with water immediately if in contact
with any body part.
• Service work performed on the A/C system must be performed in a
well ventilated work area.
• Keep open flame away from service area. The discharge of a refriger-
ant gas near an open flame can produce a very poisonous gas.
NOTE: O-rings used in a 134A system are Hydrogenated
Nitrile Butadiene Rubber (HNBR). These are green in color
and required for the 134A system.
A/C Heater:
The A/C system will also produce heat to warm the air in the dash area.
Much like the refrigeration side of the system, a liquid will be used in the
process. This liquid is the engine coolant. The coolant is passed from the radia-
tor to an electronic water valve. The water valve, when open, will allow the
coolant to flow through the heater core. The heater core is tubing and fins. Air
is drawn into the system by a blower motor through the outside recircula-
tion door opening. Air is blown through the A/C evaporator core and then
through the heater core. When the temperature control is in the
WARM
posi-
tion coolant flows through the heater core. When the temperature is in the
COOL
position coolant flow bypasses the heater core. In either position the air
flow is felt at the discharge vents.
Diagnosis of Electric Water Valve:
Theory of Operation: Models with a center dial temperature control use a
potentiometer at the control head for input of desired temperature. The water
valve, which controls the water flow to the heater core, is opened and closed by a
stepper motor mounted on the water valve. A control module compares the
output voltage from the control to that of the feedback for the stepper motor of
water valve. The control module then drives the motor to within one-half Volt of
the control potentiometer voltage.
Summary of Contents for 2002 NEPTUNE
Page 12: ......
Page 28: ...General Information 2 0 0 2 N E P T U N E 1 28 NOTES...
Page 32: ......
Page 73: ...Driving Safety 2 0 0 2 N E P T U N E 2 73 Rear View VIEWS Front View OM010726 OM010725...
Page 74: ...Driving Safety 2 0 0 2 N E P T U N E 2 74 Curbside View Roadside View OM010724 OM010723...
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Page 202: ...Water Systems 2 0 0 2 N E P T U N E 6 202 NOTES...
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Page 218: ...LP Gas System 2 0 0 2 N E P T U N E 7 218 NOTES...
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Page 279: ...Electrical Systems Chassis 2 0 0 2 N E P T U N E 9 279 NOTES...
Page 280: ...Electrical Systems Chassis 2 0 0 2 N E P T U N E 9 280 NOTES...
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Page 331: ...Chassis Information 2 0 0 2 N E P T U N E 10 331 MAINTENANCE RECORD...
Page 332: ...Chassis Information 2 0 0 2 N E P T U N E 10 332 MAINTENANCE RECORD...
Page 333: ...Chassis Information 2 0 0 2 N E P T U N E 10 333 MAINTENANCE RECORD...
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Page 337: ...INDEX...
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