Cessna 177 SERIES Service Manual page 229

15-27. TROUBLE SHOOTING--GYROS. (Cont).
TROUBLE PROBABLE CAUSE REMEDY
HORIZON BAR OSCILLATES Central filter dirty. Check filter. Clean or replace
OR VIBRATES EXCESSIVELY.
filter.
Suction relief valve im- Adjust or replace relief valve.
properly adjusted.
Faulty suction gage.
Substitute known-good suction
gage and check gyro indication.
Replace suction gage.
Defective mechanism. Substitute known-good gyro and
check indication. Replace in-
strument.
Excessive vibration. Check panel shock-mounts. Re-
place defective shock-mounts.
EXCESSIVE DRIFT IN
Central air filter dirty. Check filter. Clean or replace
EITHER DIRECTION. filter.
Low vacuum. relief valve Adjust or replace relief valve.
improperly adjusted.
Faulty suction gage. Substitute known-good suction
gage and check gyro indication.
Replace suction gage.
Vacuum pump failure. Check pump. Replace pump.
Vacuum line kinked or Check lines for damage and
leaking. leaks. Repair or replace dam-
aged lines, tighten connections.
DIAL SPINS IN ONE Operating limits have been
Replace instrument.
DIRECTION CONTINU- exceeded.
OUSLY.
Defective mechanism.
Substitute known-good gyro
and check indication. Replace
instrument.
SHOP NOTES:
Change 2 15-13