Figure 3-10. Capacitor removal and installation.

TM 5-4120-273-15

3-37. Compressor Motor Relay and

Electrical Heater Relay

a. General. Both relays are located in the junc-

tion box, figure 3-13. A motor relay starts the

compressor motor and a heater relay is connected

to the electrical heaters.

b. Removal. Refer to figure 3-13 and remove

relays.

c. Inspection and Testing.

(1) Inspect for pitted or burned contacts.

(2) Test for continuity across coil with mul-

timeter set on OHMS. Refer to wiring diagram

figure 1-5 to establish points of continuity.

d. Installation. Refer to figure 3-13, and in-

stall relays.

3-38. Rectifier

a. General. The rectifier changes alternating

current to direct current.

b. Removal. Refer to figure 3-13 and remove

rectifier.

NOTE: TAG AND DISCONNECT

ELECTRICAL LEADS AS

c. Inspection and Testing.

NECESSARY.

(1) Inspect for cracked or broken casing and

burned or damaged contacts.

ME 4120-273-15/3-10

(2) Test for continuity with multimeter set

on OHMS. Refer-to wiring diagram figure 1-5 to

Figure 3-10. Capacitor removal and installation.

establish points of continuity.

d. Installation. Refer to figure 3-13, and install

rectifier.

3-39. Heater Elements

c. Testing. Test the circuit breaker for continu-

a. General. The electrical resistance heaters are

ity with a multimeter set on OHMS. Refer to the

mounted directly behind the evaporator coil. These

wiring diagram figure 1-5 for points to establish

heaters provide the heat called for by the thermo-

continuity.

stat to maintain the required temperature of the

conditioned air. The heaters provide two ranges

d. Installation. Refer to figure 3-13 and install

of heating and are manually controlled by placing

circuit breaker.

the selector switch in the proper position (LO-

HEAT or HI-HEAT) to maintain the required

3-36. Phase Sequence Relay (Model

temperature.

CV-6-3-08-400 only)

b. Removal. Refer to figure 3-11, 3-12 and

a. General. The phase sequence relay prevents

remove the heater elements.

operation of the unit unless the phase sequence is

c. Inspection and Testing.

correct and the fan and compressor motor rotate

(1) Inspect for broken or damaged elements.

in the proper direction.

(2) Test for continuity across elements with

b. Removal. Refer to figure 3-13 and remove

multimeter set on OHMS. Refer to wiring diagram

phase sequence relay.

figure 1-5 to establish points of continuity.

c. Inspection and Testing.

d. Installation. Refer to figures 3-11, 3-12 and

(1) Inspect for cracked or broken casing.

install heating elements.

(2) Test for continuity with multimeter set

3-40. High Pressure Switch

on OHMS. Refer to wiring diagram figure 1-5 to

establish points of continuity.

a. General. The high pressure switch prevents

d. Installation. Refer to figure 3-18 and install

the compressor from operating if the head pres-

the phase sequence relay.

sure exceeds 445 psig (fig. 3-14).

3-14