Chapter 55: A/C and Heating Test

air, too much refrigerant, a restriction in the high-side, and poor airflow across the condenser.

If the high-side pressure is too high, What to suspect in the system?

Using a UV lamp, and in some cases special glasses or goggles. (Remember system leaks will be apparent by a luminous yellow-green trace.)

Explain how dye can be used to find leaks in the A/C.

Permanently minimize the risk of cross-contamination 80

Guidelines for converting (Retro fitting) R-12 to R-134a: -_______________________ install conversion fittings using a thread locking chemical. -Unique service fittings for R-134a should be used to ___________________________________________________. -Recharge the system with R-134a to _________ percent of the original R-12 charge.

a faulty metering device, poor airflow across the evaporator, a restriction in the low-side of the system, or a system that is undercharged with refrigerant.

If the low-side pressure is lower than normal, What to suspect?

It indicates that the expansion valve is flooding the evaporator.

If the suction line is covered with thick frost, What does this indicate?

D. The system being overcharged with refrigerant

In an A/C system, if the low-side pressure is lower than normal, Which of the following is the least likely cause? A. A faulty metering device B. Poor airflow across the evaporator C. A restriction in the low side of the system D. The system being overcharged with refrigerant

Belt Slippage

Inspection: -______________________ may be evident by large amounts of black dust around the clutch plate.

The entire system must be completely evacuated and a new accumulator or desiccant bag must be installed.

Service Precautions: If the system has been open for more than two minutes, explain what needs to be done to the system.

Orifice tube Flash the line, Replace Carefully, colder, same temperature

Simple checks: - On vehicles equipped with the _______________________ , feel the liquid line from the condenser outlet to the evaporator inlet. A restriction is indicated by any temperature change in the liquid line before the orifice tube. -____________________ or ____________________ the orifice tube if restricted. -________________ place your hand on the inlet line of the evaporator. Do the same on the outlet. Both tubes should be _____________ than the ambient temperature and both should be about the ___________ ______________________.

B. The system is overcharged

The high-side pressure on a system with a cycling clutch and pressure cycling switch is 245 psi, the low-side pressure is 28 psi, and the ambient temperature is 78 degrees Fahrenheit. What do these gauge readings indicate? A. The system is undercharged B. The system is overcharged C. The system is normal D. The evaporator pressure regulator is bad

True

True or False? Refrigerant gas is heavier than air, so the probe should be positioned below the test point.

False, it should be cold to touch

True or False? The suction line to the compressor should be hot to the touch from the evaporator to the compressor.

B. Correct charge of refrigerant in the system

When checking an A/C system, the evaporator's inlet and outlet tubes feel like they are at the same temperature. Which of these could cause this? A. A plugged evaporator B. Correct charge of refrigerant in the system C. Restricted orifice tube D. Leaking condenser

When you are not sure of the refrigerant used in a system or if you suspect that a mixing of refrigerants has occurred.

When should you run a purity test and/or use a refrigerant identifier?

B. The liquid line from the condenser outlet to the evaporator inlet should be cool.

Which of the following statements is not true about orifice tube system? A. The suction line must be cool to touch from the evaporator outlet to the compressor. B. The liquid line from the condenser outlet to the evaporator inlet should be cool. C. The evaporator should feel very cold. D. The accumulator must be cool to the touch.

A. low refrigerant level

While conducting a pressure test on an A/C system, the ambient temperature is 80 degrees Fahrenheit, the low-side gauge reads low (8 psi), and the high side also reads low (85 psi). Which of these could cause these readings? A. low refrigerant level B. normal operation C. bad compressor D. a high-side restriction

Testing undercharged overcharged, insufficient

_____________ Procedures: -If the observed pressures are below the normal ranges, this indicates an ________________________ system. -If both pressures are above normal pressures, the system is ______________________ or there is _______________________ air flowing through the condenser.

Refrigerant Never 60 125 degrees Fahrenheit (52 degrees Celsius) Sunlight

______________ Safety Precautions: - ______________ overfill refrigerant containers. - The filling level of the container should never exceed _________ percent of the container's gross weight rating. -Always store refrigerant containers in temperatures below __________________________________________ and keep them out of direct ___________________.

Electronic electronic test probe

______________________ Leak Detectors: -The hand-held battery-operated ______________ leak detector contains a _____________________that is moved under the areas of suspected leaks.