Section XVII: MAINTENANCE OF TRANSFORMER, RECTIFIER, AND PRESSURE SWITCHES

TM 5-4120-352-14

circuit breaker (18) through opening in junction

(3) Condenser Fan Relay. Refer to figure 4-

box with locating projection in opening provided.

19 and remove relay as follows:

Install breaker nut.

(a) Remove two screws (6), nuts (7), and

(3) Time Delay Relay, Install time delay

flat washers (8). Remove relay and bracket from

relay (17) on junction box. Secure relay to junction

junction box.

box with four screws (13), nuts (14), and washers

(b) Remove three nuts (9) and flat washers

(15).

(10) to separate bracket ( 11) from condenser fan

(4) Condenser Fan Relay. Install condenser

relay (12).

fan relay (12) on bracket (11) and secure relay with

(4) Time-Delay Relay. To remove the time

three nuts (9) and flat washers (10). Install bracket

delay relay, refer to figure 4-19 and remove relay as

on junction box and install two screws (6), nuts (7),

follows:

and washers (8).

(a) Remove four screws (13), nuts (14), and

(5) Heater and Compressor Motor Re-

washers (15).

lays. Install heater relay (5) or compressor motor

(b) Remove relay (17) and two each of

relay (4) and secure relay with four screws (1), nuts

washers (15) and (16).

(2) and flat washers (3).

(5) Control Circuit Breaker. To remove the

e. Installation.

control circuit breaker (18, fig, 4-19), remove circuit

(1) Make any electrical connections that were

breaker nut from front of junction box and pull

disconnected during removal.

breaker to the rear of the junction box.

d. Assembly.

(2) Carefully install junction box into housing

and install seven screws and Iockwashers.

(1) General. Refer to figure 4-19 and install

(3) Refer to paragraphs 4-42 and install con-

any components that were removed. After installa-

trol module.

tion of components, make all the necessary elec-

(4) Refer to figure 4-5 and install top front

trical connections.

cover.

(2) Control Circuit Breaker. Install control

MAINTENANCE OF TRANSFORMER, RECTIFIER, AND PRES-

S e c t i o n XVII.

SURE SWITCHES

4-44. General.

(1) Refer to figure 4-5 and remove top cover.

Refer to paragraph 4-43 and partially remove junc-

The power transformer and rectifier reduce the

tion box.

power voltage and convert the alternating currect

(2) Disconnect leads and check for continuity

to 24-volt direct currect to operate the coils and

across the primary winding and then across the sec-

switches in the control circuit. The transformer is

ondary winding. If eighter winding is open, replace

rated at a secondary voltage of 30 VAC with a pri-

the transformer.

mary voltage of 120 VAC. The transformer and rec-

tifier are located below the junction box. The high

(3) Check for grounds between one terminal of

each winding and transformer case and for shorts

and low pressure cutout switches are also located

between one primary terminal and one secondary

below the junction box with the reset buttons ex-

terminal using an insulation tester, megger or mul-

tending through the front of the housing. The pres-

timeter on high ohms setting. Replace transformer

sure cutout switches are connected in the refrig-

if a short or ground is indicated.

eration system and are electrically connected in the

b. Removal. With junction box removed, re-

control system to the compressor motor relay coil.

Extreme high or low pressure opens the circuit

rfer to figure 4-20 and remove four screws and lock-

washers. Disconnect and remove transformer,

causing the compressor to stop.

c. Installation. Refer to figure 4-20 and in-

stall transformer, four screws, and four lock-

4-45.

washers. Connect leads. Refer to paragraph 4-43

a. Testing. Test transformer as follows:

and install junction box.

4-40