364 Auto Heating & Air Conditioning
Copyright by Goodheart-Willcox Co., Inc.
To remove the power module, fi rst locate it under the
dashboard or hood. Then disconnect the electrical leads
and remove the fasteners holding the module to the duct.
Then pull the module from the duct. Compare the old
and new modules to ensure the new module is the correct
replacement. Then place the new module in the duct and
attach the fasteners. Reconnect the electrical leads and
check HVAC system operation
Engine and Coolant Temperature Sensors
Warning: Before removing any coolant
sensors, review the cooling system safety
precautions in Chapter 20.
Most engine and coolant temperature sensors are
located on the engine. A few sensors are installed in the
heater hoses. To remove the sensor, locate it on the engine
and remove the electrical connector.
If the sensor extends into the cooling system, depres-
surize and drain the cooling system. Then use the correct
tool to unscrew the sensor from the engine block. If the
sensor is installed on a heater hose, remove the clamps and
pull the sensor from the hose. Coat the new sensor with
sealant if required.
Caution: Some sensors must not be
installed using sealant as this will affect the
electrical fl ow between the sensor and
engine block.
Install the new sensor and tighten it into place.
Tighten the hose clamps if applicable. Refill the cool-
ing system and bleed according to the procedures in
Chapter 20. Then start the engine and make sure the
sensor is operating properly.
Note: After all repairs are made and the
HVAC system has operated for about 10
minutes, re-enter the self-diagnosis mode
and make sure no trouble codes have appeared.
Mechanical and Electromechanical
System Service
These systems have fewer parts than electronic sys-
tems. Service procedures are identifi ed in the following
paragraphs.
Adjusting Transducer Cables
All mechanical temperature control transducer cables
are adjustable. To adjust the cable, it will be necessary to
remove dashboard parts to gain access to the transducer
and control panel.
Early cables were adjusted by a turnbuckle. To adjust
this type of cable, insert a gauge tool in the transducer.
Then turn the turnbuckle until the temperature lever is in
the middle position (usually 75°F or 24°C). Then remove
the gauge tool.
Later mechanical system cables use an adjusting slot
at the transducer. To adjust the cable, move the transducer
cable arm to line up with the mark on the transducer
body. Then loosen the adjusting slot mounting bolt and
move the temperature lever to the middle position (75°F
or 24°C). Then tighten the slot mounting bolt and recheck
operation.
Replacing System Parts
Mechanical and electromechanical temperature con-
trols are easy to replace by following the instructions in the
following paragraphs. Remember to readjust the trans ducer
cable whenever the cable is disturbed.
Note: Mechanical and electromechanical
control panels are replaced in the same
way as manual control panels. Refer to
manual control panel procedures in Chapter 21.
Electromechanical sensors are replaced in the same
manner as electronic sensors.
Transducers
To replace a transducer, remove the trim panel cov-
ering the transducer air inlet. This is usually a small lou-
vered cover held by trim screws. Then remove the cable
connection and aspirator duct. Remove the vacuum lines,
and electrical connector if used. Remove the fasteners
and remove the transducer. Install the new transducer and
tighten the fasteners. Install the aspirator tube, vacuum
lines, and cable, then adjust the cable. Reinstall the air inlet
cover and recheck HVAC system operation.
Power Servo
Locate the power servo next to the blend door.
Remove the electrical connectors, vacuum line, and blend
door linkage. Then remove the fasteners holding the power
servo to the case. Remove the power servo from the case.
Place the new power servo in position and attach the blend
door linkage. Install the fasteners and reattach the vacuum
line and electrical connectors. Recheck HVAC system
operation, and adjust servo position if needed. After all
adjustments are made, reinstall other dashboard parts.