Chevrolet 10 Series 1968, Service Manual, Page: 406 / 713

ENGINE FUEL 6M-13
F ig . 7 A —Thermostatical ly Controlled A ir Cle an er
O p e ra tio n a l
1. Remove air cleaner cover and install temperature
gauge as close as possible to sensor.
2. If engine has been in decent operation allow it to
cool to below 85°F. Replace air cleaner cover with­
out wing nut.
CA U T IO N : IF INSPECTION OF CONTROL
DAMPER ASSEMBLY IS DIFFICULT DUE TO
SNORKLE TUBE POSITION, THE USE OF A
MIRROR IS RECOMMENDED.
3. Start and idle engine. When control damper assembly
begins to open, remove air cleaner cover and
observe temperature reading. Opening temperature
must be between 85° and 115°F.
4. If damper assembly does not open at the correct
temperature, continue with the following vacuum
motor and sensor checks.
5. With the engine off the position of the control damper
assembly should be in the cold air delivery mode.
6. To determine if the vacuum motor is operable apply
at least nine (9) inches of vacuum (either from the
engine or an independent source) to the fitting on
the vacuum motor.
7. The control damper should close the cold air passage
as long as vacuum is applied (the hot air pipe will be
open).
8. If the vacuum motor fails to operate the control
damper assembly with the direct application of
vacuum, check to determine if the vacuum motor
linkage is properly connected to the door or if a
bind is present.
9. If the linkage is found satisfactory, then motor re­
placement is indicated. If the vacuum motor check
is found to be satisfactory, then sensor replacement
is indicated.
VACUUM MOTOR REPLACEMENT
Rem oval
1. Remove air cleaner from engine.
2. Drill out spot welds fastening vacuum motor re­
taining strap to snorkel tube.
3. Remove vacuum motor by lifting and unhooking
linkage rod from damper door.
Replacement
1. Drill 7/64" hole in snorkle tube at center of vacuum
motor retaining strap (fig. 9A).
2. Connect vacuum motor linkage to damper door.
Fasten retaining strap to air cleaner with sheet
metal screw.
3. Replace air cleaner on engine and check operation
of vacuum motor and control damper assembly.
TEMPERATURE SENSOR REPLACEMENT
Rem oval
1. Remove air cleaner from engine and disconnect
vacuum hoses at sensor.
2. Pry up tabs of sensor retaining clip.
CHEVROLET TRUCK SERVICE MANUAL