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COMPONENT OPERATION AND
TROUBLESHOOTING
Ⅲ TOOLS NEEDED
Volt-Ohmmeter
Flat and Phillips Screw Drivers
5
⁄
16
-in. Nut Driver
Side Cutting Pliers
Before cleaning, servicing, performing maintenance
or removing the chassis from the wall sleeve, discon-
nect all power to the unit to avoid the possibility of
electrical shock and personal injury. Only trained
and qualified service personnel should perform
installation and service procedures on these units.
Untrained personnel may perform basic maintenance
tasks such as cleaning and replacing filters. Refer to
GENERAL DISASSEMBLY section of this manual
for proper procedures to disconnect power to 52S
units.
The Manufacturer reserves the right to discontinue, or
change at any time, specifications or designs without
notice and without incurring obligations.
Consider the following safety issues:
• Prior to performing any service or maintenance on
electrical equipment you must Disconnect All
Power.
• New and unfamiliar tasks should be performed under
the supervision of an experienced service technician.
• Personal protective equipment, such as safety glasses
and work gloves, should be worn.
• The floor around the work area should be clean and
free of debris.
• Make sure tools are the correct tools for job, and that
they are working properly and in good condition.
• The 52S unit may weigh up to 150 pounds. Use a lift-
ing device or ask for assistance if the unit must be
moved.
Ⅲ INDOOR THERMOSTAT (Heat/Cool and Cool Only
Units) (Figure 53) — The thermostat maintains the
selected temperature by cycling the compressor on and
off during cooling operation and the electric heater
during heating operation. The thermostat DOES NOT
switch from heating to cooling, or cooling to
heating. If the switch is in the CYCLE position, then
the fan will be cycled off when the thermostat satisfies.
A bulb heater was incorporated on models built prior
to 1996 to help provide closer temperature control. This
heater does not affect the mechanical operation of the
switch.
To verify the operation of the thermostat switch, a conti-
nuity test may be performed as follows:
1. Turn off unit power as described in GENERAL
DISASSEMBLY section.
2. Remove wire leads from thermostat. Note their loca-
tions to ease re-assembly.
3. Place one of the leads of the continuity tester on the
terminal marked 2, and the other lead on either the
terminal marked 1 or the terminal marked 3.
4. Adjust the thermostat up or down to verify the con-
tacts of the switch open and close. When verifying
continuity of a closed switch, the ohm reading should
be 0 ohms. An open switch will show OL on the
meter.
5. When testing is complete, reconnect the leads.
Ⅲ INDOOR THERMOSTAT (Heat Pump Units)
(Figure 54) — The heat pump indoor thermostat uses a
two-stage switch for the heating mode. The first stage
engages the compressor and reversing valve, and the
unit operates in normal heat pump mode. The indoor
thermostat maintains the selected temperature by
cycling the compressor on and off in cooling mode. In
the heating mode, the indoor thermostat will cycle the
compressor or the heater, depending on the difference
between the actual room temperature and the thermostat
temperature setting.
When the room temperature is more than 4 F cooler
than the indoor thermostat setting, the second heating
stage of the indoor thermostat engages the electric
heat strip. This design feature allows the user to rap-
idly warm the room with the electric heat strip by turn-
ing the thermostat to its highest setting. When room
temperatures approach the desired temperature, the user
may adjust the thermostat to a personal comfort set-
ting, which allows for normal heat pump operation.
NOTE: For outdoor temperatures below approximately
35 F (45 F for 1999 models), the outdoor frost thermo-
stat prevents heat pump mode operation and immedi-
ately engages the electric heat strip upon a call for
heating. The electric heat strip is NEVER energized at
the same time as the compressor.
BLK
OR WHT
BLK
OR WHT
GRY
FCS
GRY
BRN
COMP
IT
TBH
IT3
SW
5
6
4
1
2
3
See Legend on page 28.
FIGURE 53 — INDOOR THERMOSTAT (IT)
CONTACTS, ALL 52SE AA AND CP MODELS
27