Filter
Top Products
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