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TM 5-4120-270-15
24V DC provided by a step-down transformer and
rectifier
circuit.
The
condenser
fan
motor
and
compressor motor contactors are rated at 50 amperes.
The evaporator fan motor and heater contactors are
rated at 25 amperes.
b. Removal. Refer to figure 6-4 and remove
contactors from the junction box.
c. Disassembly. Do not disassemble unless contacts
are dirty or pitted and require cleaning or dressing.
d. Testing (fig. 6-6).
(1) 50-ampere contactors.
(a) With contactor open, test for continuity across
control coil terminals X, and X,. If coil is open, replace
contactor.
(b) With contactor open, test for continuity
across each pair of line and load terminals L,-T,, L2-T2,
and L,-T,. If continuity exists, contacts are welded or
contact springs are broken. Replace contactor.
(c) Using a multimeter on high OHM’ range, a
megger or an insulation tester, test insulation resistance
between contactor frame and each terminal in turn. If
insulation resistance is less than 0.5 megohm, replace
contactor.
Key to fig. 6-1:
11 Screw, machine, pan head, No. 10-2 x 1/2 in
1 Knob
12 Switch, thermostat
2 Rivet, blind
13 Nut, hex, locking, No. 8-32
3 Plate, instruction
14 Washer, flat, No. 10
4 Panel assy.
15 Lead, electrical, ground
5 Screw, machine, pan head, No. 8-32 x 1/2 in.
16 Nut, hex, No. 10-32
6 Switch, selector
17 Screw, machine, pan head, No. -62 x 1
7 Nut, hex, locking, No. 832
18 Connector, receptacle, electrical
8 Plate, mounting
19 Spacer
9 Clamp, loop
20 Nut, hex, No. 642
10 Washer, lock, No. 10
21 Grommet
Figure 6-1. Control panel, exploded view.
6-2
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