328 | Section 8 Electrical System ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------- Monarch SE 2004
Safety and Handling of 134A and Pag Oil:
• When working with any refrigerant system wear eye protection and
hand protection.
• Pag Oil irritates the skin. Flush with water immediately if in contact
with any body part.
• Ensure any service work performed on the A/C system is in a well
ventilated work area.
• Keep open flame away from service area. The discharge of a refrigerant
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 radiator 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 recirculation 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 position 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: The thermostat is a potentiometer. 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 potentiometer to the feedback for the stepper motor of the water valve.
The control module then drives the motor to within one-half volt of the control
potentiometer voltage.
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