34
C13. Reversing Valve
The reversing valve is the heart of the heat pump. It directs
refrigerant flow to the coils to achieve proper direction of
flow that allows the same system to supply heated or cooled
air to enter the inside atmosphere of the structure accord-
ing to occupants’ desires.
The reversing valve’s solenoid can be energized in either
HEAT or COOL mode of operation. Most Duo-Therm Heat
Pumps have the solenoid energized in the COOL mode of
operation. The Dual (Model 39424) has the solenoid ener-
gized in the HEAT mode of operation. See FIG. C19. The
solenoid on the reversing valve can be loose, this will cause
a humming noise during the off cycle; especially is the
blower shuts off with the compressor. Check the screw
holding the solenoid coil on the reversing valve for tight-
ness.
One way to check the reversing valve is to feel the refriger-
ant line at the top of the inside coil. In the COOL mode, this
line will be cool or cold to the touch. In the HEAT mode, this
line will be warm or hot to the touch. If you do not achieve
these results, direction of refrigerant flow is not correct.
The ohms resistance of the reversing valve solenoid coil is
approximately 465 ohms plus or minus (±) 10%. If ohms
reading is within this range, the solenoid coil is good. If
ohms reading is outside this range, replace the solenoid
coil.
On Model 39424, verify AC volts are to the solenoid coil
when in HEAT mode. If AC volts are NOT present, verify
wiring is correct, especially to the 9-pin terminal connector.
Check that the connection is completed through it. Next,
verify power module board and the relay are good. If AC
volts are present and solenoid coil is good, but refrigerant
flow is not proper, the reversing valve assembly needs to
be replaced.
On all other models verify AC volts to the solenoid coil when
in COOL mode. If AC voltage is NOT present, verify wiring
is correct, especially to the 6-pin terminal connector. Check
that the connection is completed through it. Next, verify
power module board is correct, then verify relay is correct.
If AC volts are present and solenoid coil is good, but the
refrigerant flow is not proper, the reversing valve assembly
needs to be replaced.
Section C - Components, cont’d.
C14. Transformer
The transformer supplies low AC volts for the control cir-
cuit on the following air conditioner models:
39025.XXX, 39035.XXX and 39045.XXX
The transformer is a 120 volt AC, 50/60 Hz. primary (line
terminals) with a 24 volt AC secondary (load terminals),
and will handle up to 20 volt-amps.
To check the transformer, first verify AC voltage is to the
line terminals. Next, verify at least 24 volt AC is on the load
terminals. If 24 volt AC is present on the load terminals, the
transformer is good. If 24 volt AC is
NOT
present on the
load terminals and AC voltage is present on the line termi-
nals, the transformer is defective. See FIG. C20.
FIG. C20
C15. Fuse, DC
A 3-amp fuse is installed in the Analog Control Box and
CCC Power Module to protect the system from shorts or
overload created by disconnecting or reconnecting com-
ponents, when DC power is still connected to the system.
One test is to remove the fuse and do a continuity check.
No continuity requires the fuse to be replaced. Another test
can be done without removing the fuse. Use a DC voltme-
ter to check between ground and to each side of the fuse.
If there is voltage on one side only, the fuse is bad and
requires replacement. See FIG. C21
FIG. C19
FIG. C21
Manual
Compliments
of
Northwest
RV
Supply
Printed
From
http://www.nwrvsupply.com
