Troubleshooting - Friedrich racservmn Service Manual

Troubleshooting Touch Test Chart: To Service Reversing Valves
VALVE
OPERATING
CONDITION
1 2
Normal Hot Cool
Cooling
Normal Heating Hot Cool
Valve will
not shift
Hot Cool
from cool to
heat.
Hot Cool
Valve will
Hot Cool
not shift
from cool to
Warm Cool
heat.
Hot Warm
Starts to
Hot Warm
shift but
does not
Hot Hot
complete
reversal.
Hot Hot
Hot Cool
Apparent
leap in
Hot Cool
heating.
Hot Cool
Hot Cool
Will not shift
from heat to
cool.
Hot Cool
Hot Cool
Warm Cool
NORMAL FUNCTION OF VALVE
3 4 5 6
Cool Hot *TVB
as (2) as (1)
Hot Cool *TVB
as (1) as (2)
MALFUNCTION OF VALVE
Check Electrical circuit and coil
Check refrigeration charge
*TVB
Cool, Hot,
as (1)
as (2)
Hot,
Cool,
*TVB
*TVB
as (1)
as (2)
Hot,
Cool,
Hot Hot
as (1)
as (2)
Warm,
Cool,
*TVB Warm
as (1)
as (2)
Hot
Warm
*TVB Hot
Hot
Warm
Hot Hot
Hot
Hot
*TVB Hot
Hot
Hot,
Hot Hot
Cool,
Hot,
*TVB *TVB
as (2)
as (1)
Cool,
Hot,
**
as (2)
as (1)
WVB WVB
Cool,
Hot,
*TVB *TVB
as (2)
as (1)
Cool,
Hot,
Hot *TVB
as (2)
as (1)
Cool,
Hot,
Hot *TVB
as (2)
as (1)
Cool,
Hot,
Hot Hot
as (2)
as (1)
Cool,
Warm,
Warm *TVB
as (2)
as (1)
* TEMPERATURE OF VALVE BODY
** WARMER THAN VALVE BODY
POSSIBLE CAUSES CORRECTIONS
TVB
TVB
No voltage to coil.
Defective coil.
Low charge.
Pressure differential too high.
Hot
Pilot valve okay. Dirt in one
bleeder hole.
Piston cup leak
Clogged pilot tubes.
Both ports of pilot open. (Back seat
port did not close).
Defective Compressor.
Not enough pressure differential at
start of stroke or not enough flow to
maintain pressure differential.
Body damage.
Both ports of pilot open.
Body damage.
Valve hung up at mid-stroke. Pumping
volume of compressor not sufficient to
maintain reversal.
Both ports of pilot open.
Piston needle on end of slide leaking.
Pilot needle and piston needle leaking.
**
Pressure differential too high.
Clogged pilot tube.
Dirt in bleeder hole.
Piston cup leak.
Defective pilot.
Defective compressor.
NOTES:
Repair electrical circuit.
Replace coil.
Repair leak, recharge system.
Recheck system.
Deenergize solenoid, raise head pressure,
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.
Stop unit. After pressures equalize, restart with
solenoid energized. If valve shifts, reattempt
with compressor running. If still no shift, replace
valve.
Raise head pressure, operate solenoid to free.
If still no shift, replace valve.
Raise head pressure, operate solenoid to free
partially clogged port. If still no shift, replace
valve.
Replace compressor
Check unit for correct operating pressures and
charge. Raise head pressure. If no shift, use
valve with smaller port.
Replace valve
Raise head pressure, operate solenoid. If no
shift, replace valve.
Replace valve
Raise head pressure, operate solenoid. If no
shift, use valve with smaller ports.
Raise head pressure, operate solenoid. If no
shift, replace valve.
Operate valve several times, then recheck. If
excessive leak, replace valve.
Operate valve several times, then recheck. If
excessive leak, replace valve.
Stop unit. Will reverse during equalization
period. Recheck system
Raise head pressure, operate solenoid to free
dirt. If still no shift, replace valve.
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.
Stop unit. After pressures equalize, restart with
solenoid deenergized. If valve shifts, reattempt
with compressor running. If it still will not reverse
while running, replace the valve.
Replace valve.
Replace compressor
35