Trane 4WHC3036 Installer's Manual page 16

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