ARMY TM 9-6115-604-12
NAVY NAVFAC P 8 633-12
4-126. EXHAUST TEMPERATURE GAGE (M6) AND THERMOCOUPLES. EXHAUST TEMPERATURE GAGE
operates on the thermo-electric principle, consists of a rugged galvanometer which measures the voltage generated by
the thermocouple on the exhaust elbow of each turbocharger Since this voltage is very small, use extreme care in
making connections that is to be sure of putting together only clean, bright, dry wires and contacts The thermocouple
element is a pair of special alloy wires enclosed In a protecting tube. A special pair of alloy (iron and constantan) wires
are used to connect the gage (M8) to each thermocouple
CAUTION
If you have to check continuity of these circuits with an ohmmeter, be sure the
EXHAUST TEMPERATURE GAGE is disconnected because battery voltage of the
ohmmeter will seriously damage the EXHAUST TEMPERATURE GAGE.
a.
Adjustments.
(1) With the EXHAUST TEMPERATURE GAGE selector switch in the off position and system wires connected
the gage should indicate cold end temperature (temperature at terminals of gage). If this reading is not
correct adjust the "Cold End Adjuster' screw until the pointer reads the correct cold end temperature. Never
set the Indicator pointer to zero mark on the scale unless the cold end temperature actually is zero degrees.
b.
Test.
(1) Tag and disconnect wires from exhaust temperature gage (Figure 4-75, Item 5).
(2) Using a multimeter set to RX1 scale, check continuity of each pair of wires going to each thermocouple.
Multimeter should read less than ten ohms through each pair of wires and thermocouple If more than ten
ohms, repair or replace wires or thermocouples.
(3) Using a short length of alloy wires (Iron constantan) connect white wire to + and red wire - to EXHAUST
TEMPERATURE GAGE No 1 + & - and No 2 + & - terminals. Twist other end of each pair of wires together.
Set exhaust temperature gage selector switch to position one and heat (with match) the twisted end of the
wires from terminals and observe meter deflection repeat for switch position two and its wires.
(4) To test complete system disconnect wires used in step 3, reconnect wires removed in step (1), remove
thermocouples from exhaust elbows (IAW Para. 3-15d(2)(a), reconnect wiring to thermocouples, heat
thermocouples probe to a known temperature and compare to exhaust temperature meter. Repair or replace
defective components if there is an error of 40 degrees or more noted.
c.
Remove. See Figure 4-75
(1) Set MAINTENANCE LOCKOUT switch S100 to MAINTENANCE.
(2) Tag and disconnect wiring to EXHAUST TEMPERATURE GAGE M6 (5)
(3) Remove mounting hardware and gage M6
d.
Install. See Figure 4-75
(1) Install EXHAUST TEMPERATURE GAGE M6 and mounting hardware
(2) Connect wires to gage M6 and discard tags
(3) Set MAINTENANCE LOCKOUT switch S100 to OPERATE.
4-127. FUEL PUMP SWITCH S8 (4, Figure 2-1). FUEL PUMP switch S8 allows manual or automatic operation of the
fuel transfer pump and is also used to turn the pump off
a.
Test.
(1) Tag and disconnect wires from switch terminals
(2) Place FUEL PUMP switch S8 in OFF position.
(3) Using a multimeter set to RX1 scale, check continuity across terminals 2 and 3, and 2 and 1 Meter should
read Infinite
(4) Place FUEL PUMP switch S8 in MANUAL position Multimeter should read zero ohm across terminals 2 and
3 Terminals 2 and 1 should read infinite.
4-189
