Specifications

6. Testing and replacing programmable defrost timer.

With electric defrost it is critical that the defrost terminate at the earliest

possible time. The defrost timer controls the following events:

A. Evaporator fans stop.

B. Compressor stops after the pump down cycle.

C. Electric heaters are energized.

NOTE: 3-wire thermodisc (single pole double throw) is used to terminate defrost when

the coil is above freezing. A maximum defrost time should be programmed into the timer

in the event the defrost termination switch fails to terminate defrost.

To test defrost timer first,

examine dial to see if time on dial

is actual time, in case either the

power has been off, or the timer

motor is not advancing. Next,

advance the timer by hand until the

defrost cycle starts. After defrost

is terminated by the thermodisc

check to see that unit returns to

normal operation, after

approximately one half hour. If not

replace defrost timer or motor.

Visually inspect for broken or

loose wire connections to defrost

timer. If a defective connection is

found, tighten or repair

connection, if not check with

multimeter to confirm power is

reaching timer. If power is going

to timer troubleshoot timer, if not

trace for source of open circuit.