Piper Cherokee Six - Page 488

PIPER
CHEROKEE SIX
SERVICE MANUAL
NOTE
The
latest
systems
which
employ
a
central
filter
in
combination
with
a
differential
vacuum
gauge
will
indicate
a
decline
in
panel
gauge
reading
when
the
filter
becomes
clogged
and vacuum
declines
below
the
recommended
value.
The
filters
should
be
replaced
when
gauge
reading
declines
below
the
recommended
value; do
not adjust
regulator.
d. Vacuum
Regulator:
1. The
vacuum
regulating
valve
seldom
needs
replacement.
Symptoms
that
suggest
replacement
are:
(a)
Chatter
as
indicated
by
rapid
fluctuation
of
the
vacuum
gauge
needle
or an
audible
sound.
(b)
Non-repeatability
of
the vacuum
gauge
reading
when
the panel
gauge
is not
suspect
or has
been
checked
against
a
known
test
gauge
(cruise
RPM
only).
2.
All modes
of
regulator
malfunction
tend
to increase
the
vacuum
power
applied
to the
gyros.
Thus,
although
excess
vacuum
is
applied,
a loss
of
vacuum
does
not occur.
3.
The
gyros themselves
act
as a limiting
device
to keep
the vacuum
power
applied
from
exceeding
safe
levels.
NOTE
If the
panel
gauge
has been
checked
and found
OK
and
the
vacuum
gauge
reading
does not
repeat
within
the
range
of 4.8
to 5.2
inches
of mercury,
then
the regulating
valve
should
be
changed.
Observe
the
usual
precautions
for
maintaining
system
cleanliness
to
avoid
premature
pump
service.
9-5. TROUBLESHOOTING.
TABLE
IX-I.
VACUUM
SYSTEM
NOTE
For
Serial
Numbers
before
32-7100001
and
32-7140001.
Trouble
Cause
Remedy
No
vacuum
pressure
Pump
inoperative,
dis-
Replace
pump.
Locate
gauge
indication.
connected.
Broken
or
trouble
and correct.
restricted
lines.
INSTRUMENTS
Revised:
8/7/74
2J20