2-1. Indicators, Controls, and Accessories.
Tester indicators and controls are shown in figure 1-
40 and listed with their functions in table 1-12.
Tester accessories are shown in figure 4-30 and
listed with their functions in table 1-13. Table 1-14
lists those accessories common to most aircraft.
2-2. Instruction Plate. The lid of the instrument
case contains an operating instruction plate that
covers all tests performed with the tester. The fol-
lowing paragraphs include all the tests as well as
test setup diagrams.
G r o u n d t h e t e s t e r w i t h t h e p i g t a il
ground wire in the power inlet cable
before using the tester.
A flashing indicator indicated an out-
of-range condition. Temperature indi-
cator is designed to drift upscale to
the out-of-range condition when input
To prevent overheating of and possi-
ble damage to the heater probes, de-
termine that all probes being used
will heat per paragraph 3-4b.
2-3. Aircraft Temperature System Check. Para-
graphs a and b give procedures necessary to check
the aircraft temperature system. Perform the pro-
cedures in the order given.
a. Thermocouple System Continuity (Heat
Rise) Check. The continuity test checks continuity
of aircraft thermocouple system by heating each en-
gine thermocouple independently and checking for
a temperature increase on aircraft temperature in-
dicator. Refer to figure 2-1 and proceed as follows:
(1) Turn FUNCTION SELECT, STD DAY,
and MASTER POWER switches to OFF position.
If continuity probe is not available perform
continuity check with applicable heater
probe. Junction box must be connected be-
tween BH405 heater cable and heater probe,
refer to Fig. 2-2.
To prevent overheating of and possible
damage to heater probe if used in place of
applicable continuity probe, insure probe
has cooled to ambient temperature before
performing temperature system accuracy
check, para 2-3 b.
(2) Connect BH405 heater cable between
HEATER CABLE receptacle on tester and applicable
(3) Place T/C INPUT switch in HEATER CABLE
position and turn PROBE CONTROL potentiometer full
(4) Turn FUNCTION SELECT switch to
HEATER PROBE, TEMPERATURE switch to
HEATER PROBE TEMP SET, and MASTER
POWER switch to ON position. Adjust PROBE
CONTROL to test temperature (approximately 700°
C). Place TEMPERATURE switch in OPERATE
L o w e r t e s t t e m p e r a t u r e s r e q u i r e a
l o n g e r s t a b i l i z a t i o n o f t i m e t h a n
higher test temperatures. When probe
c o n t r o l o v e r s h o o t s t h e t e s t t e m -
p e r a t u r e , t h e P R O B E P O W E R l a mp
t u r n s o f f t o i n d i c a t e t h a t p o w e r h as
b e e n r e m o v e d f r o m t h e c o n t i n u i ty
probe. Monitor the probe temperature
b y t u r n i n g t h e T E M P E R A T U R E
switch to OPERATE.
(5) When temperature stabilizes at test tem-
perature, PROBE POWER lamp flashes on and off
rapidly. Apply continuity probe to each aircraft
thermocouple junction. Aircraft indicator should
indicate a temperature rise as each thermocouple is
heated. A slight temperature rise on indicator is
sufficient. The continuity check determines if all
thermocouples are operating. All thermocouples
must be operating before additional tests can be
(6) In some instances, the aircraft indicator may
not be sensitive enough to detect temperature rise. If this
occurs, connect BH450 check cable to CHECK CABLE
receptacle and to engine thermocouple harness. Use
check cable adapter if required. Apply applicable con-
tinuity probe or heater probe to each aircraft ther-
mocouple junction. With T/C INPUT switch in CHECK