Page 16
Installer’s Guide
SYMPTOMS
CHECKS
YES/NO
ACTIONS
1. LED off.
1. 24V R-B & Y-B at board, with unit running?
N
Repair low voltage wiring.
Y
Complete Check #2.
2.Short FRC_DFT pin to TEST_COMMON pin. Is
defrost cycle initiated?
N
Replace defrost control.
Y
LED is bad but control will still function.
2. LED flashing very rapidly (greater than
4 times/sec) or appears to be on continu-
ously.
TEST_COMMON pin shorted to TST pin?
Y
Remove short.
N
Replace defrost control.
3. Control does not initiate a normal
defrost.
OD Temp. below 49°F.
OD Coil temp. below 35°F.?
"Delta" T increasing?
N
Check refrigerant circuits for balanced distribu-
tion of refrigerant if OD coil is frosting and
delta T is not increasing
1. LED flashing?
N
Refer to SYMPTOM #1.
Y
Complete Check #2.
2. Check for 24V Y-B at board with unit running.
N
Repair low voltage wiring.
Y
Complete Check #3.
3. Check sensors for correct mounting (connection)
and resistance.
Remount or replace sensor if necessary.
4. Short FRC_DFT pin to TEST_COMMON pin.
Is defrost cycle initiated?
N
Replace defrost control.
Y
Y-B signal or control may be intermittent
4. Control does not initiate a forced
defrost.
24V R-B & Y-B at board with unit running?
N
Repair low voltage wiring.
Y
Replace defrost control.
5. Defrost initiates manually but terminates in less than 10 seconds.
Replace defrost control.
6. Defrost initiates manually but terminates
on time.
1. Coil sensor circuit open or reading at a very high
resistance?
Y
Replace coil sensor.
2. Does OD fan cycle off in defrost?
N
Replace defrost control.
3. Windy weather preventing normal termination?
7. Defrost initiates on approximately 15/25
minute intervals.
Be sure OD coil is clean.
N
Complete Check #2.
1. Coil sensor open or reading a very
high resistance?
Y
Replace coil sensor.
2. Ambient sensor reading less than normal?
N
Complete Check #3.
Y
Replace ambient sensor.
3. OD fan off in defrost?
N
Replace defrost control.
