open gas tank VOLKSWAGEN CORRADO 1993 Repair Manual

A/C SYSTEM GENERAL SERVICING
Article Text
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 08:48PM
ARTICLE BEGINNING
1993 GENERAL SERVICING
General Servicing Procedures
USING R-12 & R-134a REFRIGERANT
HANDLING/SAFETY PRECAUTIONS
1) Always work in a well-ventilated, clean area. Refrigerant
R-134a is colorless and is invisible as a gas. Refrigerant (R-12 or R-
134a) is heavier than oxygen and will displace oxygen in a confined
area. Avoid breathing refrigerant vapors. Exposure may irritate eyes,
nose and throat.
2) The system's high pressure can cause severe injury to eyes
and skin if a hose were to burst. Always wear eye protection when
working around A/C system and refrigerant. If necessary, wear rubber
gloves or other protective clothing.
3) Refrigerant evaporates quickly when exposed to atmosphere,
freezing anything it contacts. If liquid refrigerant contacts eyes or
skin, DO NOT rub eyes or skin. Immediately flush affected area with
cool water for 15 minutes and consult a doctor or hospital.
4) Never use R-134a in combination with compressed air for
leak testing. Pressurized R-134a in the presence of oxygen (air
concentrations greater than 60% by volume) may form a combustible
mixture. DO NOT introduce compressed air into R-134a containers (full
or empty), A/C system components or service equipment.
5) DO NOT expose A/C system components to high temperatures,
steam cleaning for example, as excessive heat will cause
refrigerant/system pressure to increase. Never expose refrigerant
directly to open flame. If refrigerant needs to be warmed, place
bottom of refrigerant tank in warm water. Water temperature MUST NOT
exceed 125øF (52øC).
6) Use care when handling refrigerant containers. DO NOT
drop, strike, puncture or incinerate containers. Use Department Of
Transportation (DOT) approved, DOT 4BW or DOT 4BA, refrigerant
containers.
7) Never overfill refrigerant containers. The safe filling
level of a refrigerant container MUST NOT exceed 60% of the
container's gross weight rating. Store refrigerant containers at
temperature less than 125
øF (52øC).
8) R-12 refrigerant (Freon) will be sold and stored in White
containers, while R-134a refrigerant will be sold and stored in 30 or
50-pound Light Blue containers.
9) R-12 and R-134a refrigerants must never be mixed, as their
desiccants and lubricants are not compatible. If the refrigerants are
mixed, system cross-contamination or A/C system component failure may
occur. Always use separate servicing and refrigerant
recovery/recycling equipment.
10) Follow equipment manufacturer instructions of all service
equipment to be used. The Material Safety Data Sheet (MSDS), provided
by refrigerant manufacturer/suppliers, contains valuable information

E - THEORY/OPERATION
Article Text (p. 6)
1993 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Wednesday, March 22, 2000 09:09PM
EMISSION SYSTEMS
AIR INJECTION SYSTEM
The air injection system consists of electrically operated
air pump, inlet valve, shut-off valve (mounted between intake ports
for cylinders No. 2 and 4), and air pump control relay.
The Electronic Control Module (ECM) control operation of air
injection system air pump by completing the ground circuit of the air
pump control relay (located above brake master cylinder). In addition,
the relay operates the secondary air injection inlet valve.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
The EGR system consist of EGR valve, EGR frequency valve, and
EGR temperature sensor. All Corrado SLC models are equipped with the
EGR system. The EGR system is switched on when engine coolant
temperature reaches 122øF (50øC). The system recirculates a small
portion of exhaust gas into the intake air/fuel mixture to reduce
nitrous oxide emissions (NOx).
EGR Frequency Valve
The EGR frequency valve is mounted on back of intake
manifold. The frequency valve controls the amount of vacuum supplied
to the EGR valve. The ECM, depending on engine speed and load,
controls the frequency valve's ground circuit. In doing so, the ECM
controls the amount of recirculated exhaust gas entering the engine.
EGR Temperature Sensor
Sensor is located in EGR valve exhaust gas recirculation
channel. The EGR temperature sensor measures exhaust gas temperature.
The electrical resistance of the sensor decreases as the temperature
of the exhaust gas increases. The signal generated by the EGR
temperature sensor is ONLY used for diagnosis of the EGR system.
FUEL EVAPORATIVE EMISSIONS SYSTEM
Fuel Evaporative (Frequency) Valve
The ECM determines the duty cycle of the frequency valve to
regulate the flow of fuel vapors from fuel evaporative (carbon)
canister into engine. When no current is supplied to valve, it remains
in the open position. The valve is closed (100% duty cycle) when the
engine is started cold. A spring operated check valve inside the
frequency valve closes when the engine is off. This prevents fuel
vapors from entering intake manifold and causing a rich mixture during
engine restart.
Fuel Tank Venting
The engine speed, engine load, engine coolant temperature,
and throttle valve potentiometer input signals are used by the ECM to
control fuel tank venting. Fuel vapors from fuel tank are vented to
fuel evaporative (carbon) canister. When engine is warm and above idle