TM 55-4920-401-13&P
Table 4-11. Aircraft Indicator Check Circuit Troubleshooting Table.
Malfunction
T E M P º C i n d i c a t i o n c a n n o t b e
adjusted with A/C IND ADJ.
R a n g e o f A / C I N D A D J i s t oo
high when RESISTANCE & A/C IN-
DICATOR CHECK switch is in NULL
BAL position.
A i r c r a f t i n d i c a t o r c h e c k c i r c u it
c a b l e w i l l n o t d r i v e a i r c r a f t i n-
dicator.
Probable Cause
a. Defective A/C IND
ADJ potentiometer
b. Defective 9 vdc power
supply on probe control and
function switch board.
c . Defective RESIST-
ANCE & A/C INDICATOR
CHECK switch
d. Defective FUNCTION
SELECT switch
a. Resistor R19 open on
resistance and insulation
check board
a. Defective instrument
cable
b. Defective egt indicator
check adapter
c. Defective FUNCTION
SELECT switch
d .
D e f e c t i v e R E -
SISTANCE & A/C INDI-
CATOR CHECK switch
e. One of resistors R22,
R23, or R24 on resistance
a n d i n s u l a t i o n c h e c k
b o a r d o p e n ( D ’ A r s o n v al
indicator)
Corrective Action
a. Replace potentiometer
(25, figure FO-8).
b. Repair power supply.
c. Replace switch (18, figure 4-
38) .
d. Replace switch (32, figure 4-
37).
a. Replace resistor (25,
figure 4-38).
a. Repair or replace cable.
b. Repair or replace adapter.
c. Replace switch (32, figure
4-37).
d. Replace switch (18, figure 4-
38).
e. Replace defective resistor
(21, 20, 19).
4-13
