TM 55-4920-328-13
i.
If the millivolt signal is present at 1A5J6-A
and -B and no output signal is present at 1A5J7-A and -
B, a relay card in data multiplexer 1A5 is defective or
there is discontinuity through data selector assembly
1A2. Check the circuits through 1A2 to verify the
integrity of the switching, using figure FO-26 and table
3-1 as a guide.
NOTE
Temperature digital indicator 1A1 is provided
with a self-test feature which shorts the input
and provides an internal offset to indicate
150°F. Faulty operation of the indicator will be
found during system checkout prior to test of
an engine, as outlined in chapter 2.
j.
If a millivolt signal is present at 1A5J7-A and
-B, and no temperature is displayed on temperature
digital indicator 1Al, the indicator is faulty.
k.
Repeat steps (d) through (j) for other high
temperature circuits input at 11J18-C and -D, -E and -F,
and -G and -H.
I.
After isolation of a defective component,
deenergize all system electrical power as specified in
chapter 2.
m.
Replace the faulty unit using the part number
identification contained in chapter 7, then verify system
operation using the applicable portions of the foregoing
procedures.
5-24. Low Temperature System.
Troubleshoot the low temperature system in
accordance with the circuit information contained in
figure FO-6 and as follows:
a.
With all system power off, accomplish
continuity checks of system wiring and interconnect
cabling.
b.
Energize the METS electrical systems as
specified in chapter 2, Preliminary Checkout Prior to
Test paragraph. Allow the specified warm-up and
stabilization period.
c.
Use an appropriate voltmeter to check all ac
and dc power and signal voltage levels shown in figure
FO-6.
NOTE
If an alarm is initiated by the application of an
electrical signal in a low temperature circuit at
11J16, depress the ACK switchlight unit on
services panel 4A1 to silence the alarm.
d.
Apply +5.03mv dc to connector pins 11J16-J
and -K, using a precision dc millivolt source.
e.
Observe temperature digital indicator 1A1 for
an
indication
of
approximately
200 °F.
If
the
temperature displayed is not approximately as specified,
but there is a significant temperature indication, the
system should be recalibrated in accordance with the
calibration TB. If no temperature is displayed on 1A1,
check the millivolt signal level at pins 5(+) and 5(-) in
1A9J1.
f.
If no signal is available at the points specified
in step (e), thermocouple reference junction 1A9 is
defective.
g.
If the signal is available at 1A9J1, check the
signal output at data multiplexer connector 1A5J7-A and
-B. Verify that the applicable push-button switch (table
3-1) on data selector assembly 1A2 has been depressed
and that continuity is present through the applicable
circuit in this unit. (Refer to figure FO-26 located in the
back of this manual.)
h.
If no signal is present at 1A5J7-A and -B, a
relay card in data multiplexer 1A5 is defective.
i.
If continuity and signal level is correct
through data selector assembly 1A2 and no temperature
is displayed on unit 1A1, the temperature digital
indicator is faulty.
j.
Repeat steps (d) through (j) to isolate trouble
in the remaining 19 low temperature circuits shown in
figure FO-6.
k.
After
isolation
of
a
faulty
component,
deenergize all system power as outlined in chapter 2.
l.
Replace the defective unit, using the part
number information contained in chapter 7, then verify
system operation using the applicable portions of the
preceding instructions.
5-25. Water Temperature System.
Troubleshoot the water temperature system as
shown in figure FO-7 and as follows:
NOTE
It is assumed that continuity and input power
checks have been accomplished prior to the
start of fault isolation. A thermocouple must
be connected to the circuit in the following
procedures.
a.
Prior to a detailed checkout of all system
5-29
