Outside Air Thermostat - TM-5-4120-337-140047

and using an ohmmeter measure for continuity

in the LOW speed position. Using an ohmmeter a

a c r o s s terminals 2 and 3 of terminal board TB2 in

high resistance should be read between contacts 1

the junction box. If the temperature at the ther-

a n d 2. Place the switch in the High speed position.

mostat (located on the rear panel above the con-

Zero ohms should be read between contacts 1 and

d e n s e r coil) is above 50 F., the resistance should

be very low. An open circuit (high resistance)

c. Removal. Remove the hexagon nut which

indicates that the thermostat is defective.

s e c u r e s the switch to the front of the control panel.

c. R e m o v a l . R e m o v e t h e t w o s c r e w s w h i c h

d. Installation. Installation shall be in the

reverse order of removal.

s e c u r e the thermostat and gasket to the rear panel.

Remove the junction box from the air conditioner

4-47.

Fan Motor

and

Compressor

Motor

(para 4 - 3 6 b ) . Remove electrical plug P4 from the

Capacitors

l e f t back of the junction box. Disconnect electrical

a. Function. Two capacitors are incorporated in

connector P4 per paragraph 4-49. Unsolder only

the electrical circuit to improve the power factor,

the two wires V8D16 and V9A16 which are an

reduce motor currents, supply the required starting

integral part of the outside air thermostat.

torque for the fan and compressor motors and to

d. Installation. Installation shall be in the

i m p r o v e the efficiency of the two motors. One run

reverse order of removal.

c a p a c i t o r C2 is utilized to improve the compressor

4-49. Wiring Harness Repair

motor characteristics and the second capacitor C1

i s utilized to improve the fan motor characteristics.

a . General. Six wiring harnesses are used in the

air conditioner to distribute the control and elec-

b. Removal. Remove the junction box from the

trical power supply. If a harness is severely

air conditioner (para 4 - 3 6 d ) . Tag and disconnect

t h e four leads to the two capacitors located behind

damaged, it should be replaced. The procedures

the left side junction box mounting bracket.

c o n t a i n e d here provide for repair to minor damage.

Remove the four screws located on the lower left

b. Test and Inspection.

o u t s i d e panel of the air conditioner casing. Lift the

(1) Inspect the connectors for cracked or

capacitor and bracket assembly out of the air

damaged shells and for bent pins.

c o n d i t i o n e r . Remove the two nuts and screws which

(2) Inspect the harness wiring for broken

s e c u r e the capacitor retaining strap to the mounting

wires and frayed or damaged insulation.

bracket and remove the capacitors.

(3) Use an ohmmeter and check continuity of

c. Testing. A c a p a c i t o r s u s p e c t e d o f b e i n g

each wire from the pin of one connector to the

d e f e c t i v e should be inspected for cracks or external

corresponding pin of the other connector, (wiring

diagram fig. 1-5). Ohmmeter should read ap-

deformation. If a visual defect is observed the

proximately zero ohms.

c a p a c i t o r may be assumed to be defective. Shorted

fuses or a tripped circuit breaker is an indication

( 4 ) Check continuity between each pin and all

other pins on all connectors. Infinite ohms should

t h a t a capacitor is shorted. A shorted run capacitor

exist between all pins, unless connected as shown

will also run hot. If the compressor or fan motor

on wiring diagram.

starts and runs but fails to carry the load or trips

c. Disassembly.

out the protector when not overloaded, an open

running capacitor is indicated. Take an amp

(1) Disassemble the connector to gain access

to the wiring soldered to the connector pins.

reading of the motor associated with a suspect

(2) To remove a wire, unsolder it from the

c a p a c i t o r with the capacitor both in and out of the

p i n s on each connector and pull the wire from the

circuit. If the current draw of the motor does not

harness assembly.

i n c r e a s e with the run capacitor out of the circuit, it

indicates an open capacitor. The capitance rating

( 3 ) To remove a connector, unsolder all wires.

one at a time, from the connector to be removed.

may be checked using the procedures specified in

Tag each wire as it is unsoldered.

paragraph 4-43b. Test voltage shall not exceed

d. Reassembly. Reassemble the connector shells

370 volts for this test.

i n reverse order of removal. Be sure that the shell

d. installation. Installation shall be in the

reverse order of removal.

insulator is in place and not damaged.

4-48. Outside Air Thermostat

4-50. Heating Elements

a. Function. The outside air thermostat is a

a. Function. There are two banks of three

normally open device which opens at 50 F. to

heating elements per bank. Their purpose is to

prevent operation of the compressor below this

p r o v i d e heated air on demand. They are controlled

temperature.

by a relay and a selector switch. When the mode

b . Testing. R e m o v e t h e f r o n t a c c e s s p a n e l ( p a r a

s e l e c t o r switch is placed in LO-HEAT position, one

4-12) and the junction box cover (para 4 - 3 6 b ) .

bank of three heating elements is energized; with

P l a c e the mode selector switch in the OFF position

the selector switch in HI-HEAT position, both

4-15