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DEFROST
CONTROL
TROUBLESHOOTING
FLOWCHART
START HERE
I
Check control transformer
primary
and secondary voltages.
Repair or
replace as necessary.
I
Turn off power to unit.
I
Check defrost sensor. Is sensor
temperature
or pressure
acti-
vated? For help in determining,
re-
fer to operation of control in unit
installation instructions
and unit
wiring diagram.
I
I
I
Pressure
Temperatu re
I
Is sensor making good
contact with coil?
Yes _
No
I
Repair or
replace sensor
bracket.
Check all electrical connections
at the defrost control. Defrost
sensor and defrost relay.
I
Connect a jumper across
the defrost relay.
I
Connect a jumper across the two
"TST" pins on the delrost Control,
I
Turn indoor thermostat to
heat mode and adjust to high-
est temperature
setting.
1
Turn on power to unit.
I
Check voltage across "HLD"
terminal and "COM" termi-
nal, Is voltage 24 + 6VAC?
1
I
ls solenoid engaging?
Yes _t
No
i
1
Replace reversing
Replace solenoid.
valve. Repeat
Repeat troubleshoot-
troubleshooting
ing procedure,
procedure.
Yes
............
i ....
1 .o___1
Is defrost control set for
Is compressor
contactor
30, 60 or 90 minute de =
energized?
frost intervals?
i---No ................
I Yes
Check thermostat and
thermostat widng. Repair
or replace as necessary
I
Repeat troubleshooting
procedure.
Does un_ go into defrost
t
within appropriate
time?
I
Repeat troubleshooting
|
Yes
No _
procedure.
i
]
Unit is operating properly.
Check voltage across "OUT"
Turn off power to unit,
terminal and "COM" terminal.
Remove all test jumpers.
Is voltage 24 ± 6VAC?
Reassemble unit.
Yes
I
Connect a jumper between "OUT" terminal
and "COM" terminal. CAUTION-Be
careful
not to short "OUT" terminal to "24v" terminal,
Permanent
controt damage could result.
I
Does unit go immediately
into defrost?
Yes
t
I
Turn off power to unit.
Remove all test jumpers.
Replace defrost control with new
control board,
Repeat troubleshooting
procedure.
Check circuit from "HLD"
terminal back to thermo-
stat, Repair or replace
as
necessary.
Yes
Check voltage across re=
versing valve coil. Is volt-
age 24 ÷ 6VAC?
I
I
No
No
I
Turn off power to unit.
Check and repair circuit
from reversing valve
through defrost relay to
control transformer.
Repeat troubleshooting
procedure.
Check voltage across de-
frost relay coil.
Is voltage
24 ± 6VAC?
I
["-_
Yes _
No
Is defrost relay
energized?
I
No
Check voltage across "24Y"
terminal
and "COM" terminal.
Is
voltage 24 ± 6VAC?
I
_ .....
Yes
I
Turn off power to unit.
Replace defrost relay,
Repeat troubleshooting
procedure.
NO
,,,, ,,,,,,
I
Turn off power to unit.
Check circuit from defrost
switch back to control
transformer.
Repair of re-
place as necessary,
Repeat troubleshooting
procedure,
Page 4
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