Friedrich Twintemp, Service Manual

Page: 35 / 68

Reversing Valve in Heating Mode
TESTING ThE COIL
The solenoid coil is an electromagnetic type coil mounted
on the reversing valve and is energized during the
operation of the compressor in the heating cycle.
1. Turn off high voltage electrical power to unit.
2. Unplug line voltage lead from reversing valve coil.
3. Check for electrical continuity through the coil. If you
do not have continuity replace the coil.
4. Check from each lead of coil to the copper liquid line
as it leaves the unit or the ground lug. There should
be no continuity between either of the coil leads
and ground; if there is, coil is grounded and must be
replaced.
5. If coil tests okay, reconnect the electrical leads.
6. Make sure coil has been assembled correctly.
NOTE: Do not start unit with solenoid coil removed from
valve, or do not remove coil after unit is in operation. This
will cause the coil to burn out.
ChECKING ThE rEvErSING vALvE
NOTE: You must have normal operating pressures before
the reversing valve can shift.
Check the operation of the valve by starting the system
and switching the operation from “Cooling” to “Heating”
and then back to “Cooling”. Do not hammer on valve.
Occasionally, the reversing valve may stick in the heating
or cooling position or in the mid-position.
When sluggish or stuck in the mid-position, part of the
discharge gas from the compressor is directed back to the
suction side, resulting in excessively high suction pressure.
Should the valve fail to shift from coooling to heating, block
the air flow through the outdoor coil and allow the discharge
Reversing Valve in Cooling Mode
ELECTRIC SHOCK HAZARD
WARNING
Unplug and/or disconnect all electrical power
to the unit before performing inspections,
maintenances or service.
Failure to do so could result in electric shock,
serious injury or death.
Sealed Refrigeration System contains refrigerant
and oil under high pressure.
Proper safety procedures must be followed,
and proper protective clothing must be worn
when working with refrigerants.
Failure to follow these procedures could
result in serious injury or death.
WARNING
HIGH PRESSURE HAZARD
pressure to build in the system. Then switch the system
from heating to cooling.
If the valve is stuck in the heating position, block the air
flow through the indoor coil and allow discharge pressure
to build in the system. Then switch the system from
heating to cooling.
Should the valve fail to shift in either position after
increasing the discharge pressure, replace the valve.
Dented or damaged valve body or capillary tubes can
prevent the main slide in the valve body from shifting.
If you determing this is the problem, replace the reversing
valve.
After all of the previous inspections and checks have
been made and determined correct, then perform the
“Touch Test” on the reversing valve.
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