Amana VCA Service Instructions Manual page 34

SERVICING
INTEGRATED DEFROST CONTROL (RHA-B2*,
RHE**A*B/D & RHF** mdls)
1. The following checks may be made with a VOM. Mea-
suring the voltage between:
a) (C) common terminal to the lower (DF) terminal,
reads 24VAC if the defrost sensor is closed (only if the
contactor coil is energized).
b) (C) common terminal to (W2) will read 24VAC during
defrosting.
c) (C) common terminal to either (O) terminals will read
zero in the heating mode and 24VAC in cooling or
defrost.
d) (C) common terminal to (PS2 terminal A) will read
24VAC when all pressure switches are closed.
e) (C) common terminal to (Y OUT) will read 24VAC
when the contactor coil is energized.
f) (FAN) left and (FAN) right terminals will read zero
when not in defrost and 230VAC when in defrost.
2. If the defrost sensor is not closed, place a jumper wire
between both terminals marked “DF”.
3. The contactor coil must be energized to initiate a defrost
cycle. Also a coil load must be on the (O and OUT)
terminals, if bench testing the defrost control.
4. With a VOM connected to (C) and (W2), move the time
select jumper to the “TEST” position. Test time will take
up to 42 seconds, depending on prior run time, before
initiating defrost. (Ranco board will take up to 14 sec-
onds). Remove the jumper quickly when defrost starts,
to allow the control to terminate defrost when the sensor
opens. If the jumper is left on “TEST”, the defrost mode
will end in about 7 seconds.
T2 Terminal
OD Fan Common
COM
Y OUT
CC
A
PS2
T'stat LPC
B
B
PS1
A
DT
DF
O
RS OUT
34 Rev 1
LED's
90
60
30
E
C
R
ATK
W2
O
Y
1. The board will ignore the jumper if left in the test position
for more than 5 minutes. It will go back to normal timing,
using a 90 minute defrost interval. To start over, remove
the jumper and cycle 24VAC power off for 1 minute.
(Ranco board remove and replace the jumper to start
over)
2. The board will ignore the test speed up mode if powered
up with the jumper in the “TEST” position.
3. If the jumper is missing from the board, the control will
default to a 90 minute defrost interval.
4. The “TEST” position of the jumper may be used to speed
up the short cycle lockout time.
5. The (FAN) terminals are the only high voltage terminals
on the board.
ADAPTIVE DEFROST CONTROL (RHD/RHE mdls)
1. Jumper defrost control (30/60) by placing jumper wire
from (R) wire of low voltage terminal board, to (SEN)
terminal of defrost timer board.
2. Using a VOM, measure voltage between (SEN) terminal
and (COM) terminal of defrost timer board - should read
24 VAC.
3. Connect VOM between (SEN) terminal and (OUT) ter-
minal - should read 0 VAC. If it reads 24 VAC, board may
be in defrost mode.
4. With VOM still connected, and the unit in operation, short
or jumper two TST terminals on board. (Test Terminals
Jumpered - Count time speeds up - 90 minutes =
approximately 21 seconds).
5. Watch VOM - should read 24 VAC at end of frost build
interval, - then read 0 VAC at end of defrost interval (about
2 to 3 seconds after first reading).