Exam 64: Heating and Air-Conditioning System Diagnosis

Technician A says heater temperature may be controlled by regulating the amount of coolant flowing Through the heater core. Technician B says heater temperature may be controlled by regulating the amount of air flowing through the heater core. Which technician is correct?

The ambient temperature is 70° F and the humidity is low. What should the high side gauge pressure be (AC system on)?

Technician A says refrigerant leaks are most common where components join together. Technician B says many manufacturers put leak-tracing dye in the refrigerant systems of new vehicles. Which technician is correct?

What must the technician do before checking an air conditioning system for refrigerant leaks using a black light?

Technician A says AC system lines and hoses that are cold have lower refrigerant pressure than warmer lines and hoses. Technician B says frost on a system component usually indicates a refrigerant leak in that area. Which technician is correct?

An air conditioning performance check requires a ________.

If the performance test shows less than 45° F at the center vent, the AC is working normally.

The outlet line from the evaporator should be ________.

Technician A says oily residue on hoses, components, or fittings indicates an area where refrigerant may be leaking. Technician B says damaged condenser fins may cause inefficient air conditioning operation at all blower speeds. Which technician is correct?

On a cold day it is normal for the thermostat to stay closed for more than 15 minutes.

Technician A says electronic leak detectors make a noise when a leak is detected. Technician B says that often the same leak detector can be used for R-12 and R 134a. Which technician is correct?

An AC system has had about 0.5 lbs of R-22 refrigerant added. What would this cause?

Technician A says that evaporator leaks can be detected by installing dye into the system and looking for yellowish-green dye stains. Technician B says that a leak at the evaporator can be detected by removing the blower motor resistor pack and inserting an electronic leak detector probe into the air stream. Which technician is correct?

Technician A says a thermostat which opens too soon can cause poor heater operation. Technician B says low coolant level can cause poor heater operation. Which technician is correct?

It is 90°F in the shop and the humidity is high. What pressure will be shown on the high side pressure gauge (AC system on)?

Technician A says that with a properly operating air-conditioning system, the inlet to the compressor should be cold and the outlet from the compressor hot. Technician B says that the condenser should be hot and the evaporator cold. Which technician is correct?

A customer complains that the heater works sometimes, but sometimes only cold air comes out while Driving. Technician A says that the water pump is defective. Technician B says that the cooling system could be low on coolant. Which technician is correct?

Technician A says that one heater hose should be hot and the other hose cool if the heater is functioning okay. Technician B says that both hoses should be hot to the touch. Which technician is correct?

If both the low side and the high side show low readings, what might be the problem?

Technician A checks ambient temperature as part of an AC performance test. Technician B says that if the AC compressor has not been operating, the high side and low side refrigerant pressure should be equal. Who is correct?