Chapter 8- Troubleshooting & Service Procedures
The low side gauge needle may fluctuate in an
above normal range as the clutch cycles. This may
be an indication that the thermostat is set too high
(someone may have attempted to adjust the fac-
tory setting). A new thermostat may have been
installed incorrectly (capillary tube not inserted
tion).
The thermostatic switch is not functioning prop-
Cause:
erly or at all.
Repair Procedure:
Replace the thermostatic switch. When you re-
move the old thermostat, replace it with one of the
same type. (They operate in a factory preset tem-
perature range.) Take care in removing and han-
dling the thermostat and thin capillary tube at-
tached to it. Don't kink or break the tube.
Position the new thermostat capillary tube at or
close to the same location and seating depth be-
tween the evaporator coil fins as the old one. Con-
nect the electrical leads.
See the Thermostat section in Chapter 10. Fan
Note:
clutch, radiator shutter, condenser, compressor,
and the newer air and water valve control sys-
tems are covered in Chapter 10.
Review of Frequent Problem Areas
In HVAC systems a limited number of things can go wrong. Moving parts of the
compressor, clutch, and expansion valve or refrigerant metering device can
malfunction or break down from metal fatigue, contamination, abnormal pres-
sure or lack of lubrication. Electrical connections may corrode, become discon-
nected or break. Fuses blow from shorts or overload. Belts slip or break.
Vibration from the engine or road surface can work bolts and air or vacuum
lines loose, or rub and break or wear parts out. Motors may burn out. The
inside of the system can become contaminated from moisture, air or desiccant
material breakdown. Refrigerant may leak out of the system quickly or very
slowly. Moisture in the system can combine with refrigerant to form acid and
attack (corrode) metal parts from the inside. Moisture and refrigeration oil can
combine to form sludge that may block refrigerant flow.
The following problems are discussed in more detail in this section: