Friedrich SM21L30-A, Service Manual

Page: 15 / 36

15
NORMAL FUNCTION OF VALVE
VALVE
OPERATING
CONDITION
DIS
C
H
A
R
G
E
TU
BE
fr
o
m
Co
m
p
re
sso
r
SU
C
T
IO
N
TU
B
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t
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Co
m
p
re
s
s
o
r
Tu
b
e
t
o
I
N
S
ID
E
COI
L
Tu
b
e
t
o
O
U
T
S
ID
E
COI
L
LE
F
T
P
ilo
t
Ca
p
ill
a
ry
T
u
be
RIG
H
T
P
ilo
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p
ill
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ry
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u
be
NOTES:
* TEMPERATURE OF VALVE BODY
** WARMER THAN VALVE BODY
1 2 3 4 5 6 POSSIBLE CAUSES CORRECTIONS
Normal Cooling
Hot Cool
Cool
as (2)
Hot
as (1)
*TVB TVB
Normal Heating
Hot Cool
Hot
as (1)
Cool
as (2)
*TVB TVB
MALFUNCTION OF VALVE
Valve will not
shift from cool
to heat.
Check Electrical circuit and coil
No voltage to coil. Repair electrical circuit.
Defective coil. Replace coil.
Check refrigeration charge
Low charge. Repair leak, recharge system.
Pressure differential too high. Recheck system.
Hot Cool Cool,
as (2)
Hot,
as (1)
*TVB Hot
Pilot valve okay. Dirt in one bleeder hole.
De-energize solenoid, raise head pres-
sure, reenergize solenoid to break dirt
loose. If unsuccessful, remove valve, wash
out. Check on air before installing. If no
movement, replace valve, add strainer to
discharge tube, mount valve horizontally.
Piston cup leak
Stop unit. After pressures equalize, restart
with solenoid energized. If valve shifts,
reattempt with compressor running. If still
no shift, replace valve.
Valve will not
shift from cool
to heat.
Hot Cool
Cool,
as (2)
Hot,
as (1)
*TVB *TVB Clogged pilot tubes.
Raise head pressure, operate solenoid to
free. If still no shift, replace valve.
Hot Cool
Cool,
as (2)
Hot,
as (1)
Hot Hot
Both ports of pilot open. (Back seat port did
not close).
Raise head pressure, operate solenoid to
free partially clogged port. If still no shift,
replace valve.
Warm Cool
Cool,
as (2)
Hot,
as (1)
*TVB Warm Defective Compressor. Replace compressor
Starts to shift
but does not
complete
reversal.
Hot Warm Warm Hot *TVB Hot
Not enough pressure differential at start of
stroke or not enough fl ow to maintain pres-
sure differential. Check unit for correct operating pressures
and charge. Raise head pressure. If no
shift, use valve with smaller port.
Body damage. Replace valve
Hot Warm Warm Hot Hot Hot Both ports of pilot open.
Raise head pressure, operate solenoid.
If no shift, use valve with smaller ports.
Hot Hot Hot Hot *TVB Hot Body damage. Replace valve
Valve hung up at mid-stroke. Pumping vol-
ume of compressor not suffi cient to maintain
reversal.
Raise head pressure, operate solenoid.
If no shift, use valve with smaller ports.
Hot Hot Hot Hot Hot Hot Both ports of pilot open.
Raise head pressure, operate solenoid.
If no shift, replace valve.
Apparent
leap in heating.
Hot Cool
Hot,
as (1)
Cool,
as (2)
*TVB *TVB Piston needle on end of slide leaking.
Operate valve several times, then recheck.
If excessive leak, replace valve.
Hot Cool
Hot,
as (1)
Cool,
as (2)
** WVB ** WVB Pilot needle and piston needle leaking.
Operate valve several times, then recheck.
If excessive leak, replace valve.
Will not shift
from heat to
cool.
Hot Cool
Hot,
as (1)
Cool,
as (2)
*TVB *TVB Pressure differential too high.
Stop unit. Will reverse during equalization
period. Recheck system
Clogged pilot tube.
Raise head pressure, operate solenoid to
free dirt. If still no shift, replace valve.
Hot Cool
Hot,
as (1)
Cool,
as (2)
Hot *TVB Dirt in bleeder hole.
Raise head pressure, operate solenoid.
Remove valve and wash out. Check on
air before reinstalling, if no movement,
replace valve. Add strainer to discharge
tube. Mount valve horizontally.
Hot Cool
Hot,
as (1)
Cool,
as (2)
Hot *TVB Piston cup leak.
Stop unit. After pressures equalize, restart
with solenoid de-energized. If valve shifts,
reattempt with compressor running. If it
still will not reverse while running, replace
the valve.
Hot Cool
Hot,
as (1)
Cool,
as (2)
Hot Hot Defective pilot. Replace valve.
Warm Cool
Warm,
as (1)
Cool,
as (2)
Warm *TVB Defective compressor. Replace compressor
TROUBLESHOOTING TOUCH TEST CHART: TO SERVICE REVERSING VALVES