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10-9

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Chapter Start - Table of C

o

ntents

- Index

Solenoid Valve—

Located on the HVAC unit or near the water valve.

It receives power from the circuit board and controls the air supply to the

water valve.

Air operated Water Valve—

The preferred location is on the engine

side of the firewall. Air pressure to the water valve is controlled by the

opening and closing of the solenoid valve. When the solenoid valve is open,

air pressure closes the water valve. The water valve is located on the inlet

side of the heater core.

You will need Constant Temperature Control analyzers to troubleshoot

the CTC™ systems. The vehicle must be operating at proper engine

coolant temperature, air pressure and voltage output in order to trouble-

shoot the two possible failure modes.

Servicing and Repairing the Heater

Heater service and repair may be necessary because of lack of maintenance.

The rubber parts: belts, heater and radiator hoses all fail in time. Engine

coolant should be replaced every year and the whole system should be flushed

when this is done. The thermostat and radiator pressure cap may fail from

metal fatigue.

Heater valves (water and air), the core, or control devices may malfunction

and require adjustment or replacement. In addition to your normal tool chest

items, the cooling system test equipment required is described in

Chapter 6

.

Summary

By now you should have a pretty good idea about what is involved in HVAC

function, service and repair. With a sound knowledge and understanding of

fundamentals and typical problem areas, your experience on the job will

quickly add to your ability and confidence.

Chapter 11

gives you a better

understanding of where components may be located and how they go together.

A series of photos and exploded view illustrations of the typical air conditioner,

heater and combo systems are described. Before you study them, you might

want to review the photos and drawings in earlier chapters.

HVAC Control System Variations