WD Catalog 2018

7-9

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Table of Contents

Index

Performance Inspection

SIGHT GLASS

CLEAR

FOAM, BUBBLES

OR MIST

STREAKED

CLOUDED

• SYSTEM OK

• OVERCHARGE

• NO REFRIGERANT

• LOW ON

REFRIGERANT

• MAY BE AIR

IN SYSTEM

• MAY BE LOW ON

REFRIGERANT

• MAY BE OIL STREAKS

AS OIL CIRCULATES

• DESSICANT

BREAKDOWN

• CONTAMINATED

SYSTEM

• A FEW INTERMITTENT

BUBBLES DURING

CLUTCH CYCLING

IS OK

Note:

A roof mounted condenser or AC unit assembly often

includes a roof mounted receiver-drier (and sight

glass) close to the condenser.

Heater System Inspection

A heater system inspection is really a combination engine cooling system and

heater inspection. All heater/cooling system rubber parts deteriorate due to the

air (ozone), heat, coolant and oils. They should be replaced at regular intervals

to prevent breakdown on the road. Metal parts and gaskets are subject to

malfunction or breakdown due to fatigue and corrosion.

Coolant has a limited life and should be replaced regularly. If it is dirty, the

cooling system should be drained and flushed or back flushed (using special

equipment) before refilling with clean water and anti-freeze. Coolant must be

hot when using the hydrometer to check protection (freeze-up) level. The

following inspection procedures are explained in more detail below:

1. Check Heater Control Valve Function

2. Inspect Other Functions

1. Check Heater Control Valve Function

Many air conditioner/heater systems depend on the heater control valve

for temperature control and positive closure. You can easily check heater

control valve function as follows.

A. Cool engine

– Start with the engine cool, set the temperature to

cold and leave the fan off. As the engine warms up, feel the heater

return hose. If the hose feels warm or hot, the heater control valve is

leaking internally. This type of leak can seriously reduce air condi-

tioning performance.

Figure 7-7

These drawings illustrate

conditions you may observe

in the sight glass window.