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May 15/77 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 21-61-0 Page 105
1. Temperature Control System Test
A. General
(1)
Two tests are presented for checking the temperature control system. The first, Temperature Control System Electrical Test, requires only that electrical continuity and functional ability of all components of the systems. However, the pack valve will not open without pneumatic pressure in the system. To simulate an open position of the valve to do the test, the electrical connector on the side of visual indicator (valve closed switch) should be disconnected. The procedure for disconnecting the connector is noted in the applicable step. The second, Temperature Control System Operation Test, requires operation of cooling packs which means that in addition to electrical power the pneumatic system must be pressurized. This check also proves the system to be operationally correct, however it checks only the response to normal operation.
(2)
The following tests are written for the passenger cabin temperature control system. The control cabin system is identical except respective control components must be used and only one system may be tested at a time.
(3)
It is recommended that 20-10-171, Maintenance Practices, be reviewed before using heating equipment on temperature control system components during this test.
B. Temperature Control System Electrical Test
(1) Equipment and Materials
(a) Temp Cal Probe Heater BH 3884-40 (attachment to Jet Cal engine analyzer) or H294 Temp Cal Thermal Switch Tester, or H394 Temp Cal Tester with adapter cable BH405 BH24944 Heater Probe Kit (basic P/N)
NOTE: This kit is necessary to use the testers listed above. Consult with the supplier for the appropriate dash number for a specific airplane model and tester combination.
Howell Instruments
3479 West Vickery Blvd.
Fort Worth, Texas 76107
(b)
Controlled cooling source, if ambient temperature is 85°F (30°C) or above
(c)
Standard Thermometer (°F or °C)
(2)
Prepare to Test Temperature Control System
(a)
Remove aft bulkhead of forward cargo compartment.
(b)
Provide electrical power.
(c)
Open air conditioning equipment bay doors.
(d)
Check that all air conditioning circuit breakers on panel P6-3 and P6-4 are closed and that air conditioning switches are off.
(e)
Move LIGHTS switch on pilots' center panel to TEST position and check that DUCT OVERHEAT light on overhead panel and master caution annunciators on light shield come on.
(3)
Test Manual Control
(a)
Move AIR TEMP selector knob to PASS CABIN.
(b)
Record indicator reading.
(c)
Move selector knob to SUPPLY DUCT.
(d)
Check that indicator reading is approximately the same as that recorded in step (b).
(e)
Move selector knob back to PASS CABIN and check that temperature sensor fan is operating.
NOTE: A thin sheet of paper or streamer held at air inlet grille will verify air movement.
(f)
Apply heat to the passenger cabin temperature bulb and check that temperature indicator reading goes up. Do not heat temperature bulb enough to cause the indicator to go off scale.
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CAUTION: IF TEMPERATURE APPLIED IS ENOUGH TO CAUSE INDICATOR NEEDLE TO MOVE PAST ITS LIMIT, THE UNIT MAY BE DAMAGED.
NOTE: It will be necessary to remove the bullnose cover and the temperature bulb from the sensor duct before heat may be applied directly to the bulb. As an alternate method, hot or cold air may be blown through the sensor duct inlet to raise or lower bulb temperature.
(g)
Check that mix valves are in the full cold position.
(h)
Disconnect electrical connector from side of visual indicator or pack valve.
(i)
Move the PACK switch to ON.
(j)
Hold the temperature selector knob to manual WARM until the CABIN AIR MIX VALVE indicator moves to full HOT.
NOTE: Full HOT is indicated when the pointer aligns with the inner of the two closely spaced index marks at HOT end of the indicator scale. Full COLD is at the inner of the two closely spaced index marks at the other end of the scale.
(k)
Check that indicator on mix valve has also moved to the full hot position.
(l)
Hold temperature selector knob in the manual COOL position until indicator reads full COLD.
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