Wheel Alignment: Caster/Camber Adjustment

Caster affects steering stability and steering wheel returnability. Zero (0) caster is present when the upper ball joint or top strut bearing and lower ball joint are in the same plane as viewed from the side of the vehicle. Positive caster exists when the upper ball joint or top strut bearing is toward the rear of the vehicle in relationship to the lower ball joint. When the upper ball joint or top strut bearing is toward the front of the vehicle in relationship to the lower ball joint, negative caster is present. If the caster at both wheels is not equal, the vehicle will tend to drift toward the side with the lowest caster.

Examples of the screens available on the latest alignment machines.

Camber is the inward or outward tilt of the top of the wheel. Adjusting camber centers the vehicle’s weight on the tire. Proper camber adjustment minimizes

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Air-Conditioning Performance Testing

Performance testing provides a measure of A/C system operating efficiency. A manifold pressure gauge set is used to determine both high and low pressures in the refrigeration system. The desired pressure readings will vary according to temperature. Use temperature/pressure charts as a guide to determine the proper pressures. At the same time, a thermometer is used to determine air discharge temperature in the passenger compartment.

SERVICE VALVES
System service valves provide the attachment point for the manifold pressure gauge set. They are located in the low and high sides of most A/C systems. Two basic types of service valves were used on R-12 systems: stem and Schrader. R-134a systems have quick-connect fittings. The fittings for the gauges are connected to the system’s fittings. The gauge’s fitting has a knob that is turned in the clockwise direction to open the valve. No refrigerant should leak out when the gauge set is connected.

A thermometer is used to determine air discharge temperature in the passenger compartment.

Stem Valves. The stem valve was sometimes used on twocylinder reciprocating-piston compressors. The service valves are mounted on the compressor head. These valves can be used to

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Air-Conditioning Diagnosis: Noise and Odors on Your A/C system?

Often diagnosis of an A/C system can be done by observing the operation of the system, including listening for noises. When abnormal noises are heard, they can lead to the problem area.

A typical cabin air filter and housing.

NOISE
Often a customer’s concern is the noise emitted by the A/C system. The following discussion covers the common abnormal noises and their causes.

1. Clutch Noises. The clutch normally makes a clicking noise when it engages and disengages. This noise will become louder as the clutch wears. Once the clutch is severely worn, it will make a squealing noise when it is engaged. This noise can also result from oil on the clutch. A very loud screech or squeal can indicate a seized compressor. A bent drive pulley also can cause a growling or rubbing noise.
2. Hose Noise. The change in pressures in the suction/discharge hoses can set up vibrations that cause sounds to appear from the inside of the vehicle. The noise is typically caused by

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