Cessna 1969-1976 172 Series Service Manual page 252

16-33. TROUBLE SHOOTING (Cont).
TROUBLE
PROBABLE CAUSE
I
REMEDY
Faulty contacts in external
power contactor.
5. With master switch off and
ground power applied, check for
voltage drop between two large
terminals of external power
(turn on
taxi light for a
load).
Normal indication is z e r o volts.
I f voltage is intermittently p r e s -
ent or present all the time,
replace contactor.
.
~ ~~~~~
Figure 16-2. Ground Service Receptacle Installation
16-8 Change 3