Service manual

10
Grounded Capacitor
When testing for a grounded capacitor, perform a continuity
check between each terminal on the capacitor and the bare
metal of the capacitor case. Any indication of a circuit
(constant resistance) from either terminal to case, indicates a
grounded capacitor. Grounded capacitors are defective and
must be replaced.
Indicator moves to the right side of
the scale and stays there
(indicating a completed circuit).
The capacitor is grounded.
10. Start Capacitor
Most models use a start capacitor and a start relay to give the
compressor high starting torque. The compressor will,
therefore, start against normal pressure difference (head
pressure minus suction pressure) even when shut down for a
short period of time. The start relay will disconnect the start
capacitor when the motor reaches approximately 75%
running speed.
11. (A) Start (Potential) Relay
The start relay consists of –
1) Normally closed contacts internally between
terminals #1 and #2 which switch in the start
capacitor in parallel to the run capacitor during shut
down and then switch out the start capacitor when
the motor reaches approximately 75% normal
running speed.
2) A high voltage coil internally between terminals #5
and #2 to actuate the contacts. The coil is too weak
on line voltage to actuate the contacts, but it is
connected in series with the start winding and it gets
the generated voltage of the start winding portion of
the compressor motor. This generated voltage is
much higher than line voltage and varies with the
speed of the motor. Therefore, since the relay is
designed to open the contacts at 75% of normal
running voltage (measured between terminals #5 and
#2), the contacts will open (thus disconnect the start
capacitor) at approximately 75% of normal running
speed.
11. (B) Positive Temperature Coefficient Resistor
(Commonly Known As PTCR Start
Device)
The resistor acts like a potential relay in that it takes the start
capacitor out of the start circuit, but uses resistance of
electrical flow (back EMF from compressor) instead of
opening a set of contacts. The service person should be careful
handling the resistors. They will be hot during operation (up
to 160 degrees F). The air conditioner needs to be off for 3-5
minutes during cycle time and when servicing to let the
resistor cool down.
12. Heating Element
The heating element is a resistance heater of 1600 watts (5600
BTUH) capacity and is connected across the line when the
selector is set for heating and the thermostat is calling for heat.
The current draw of the heater (element only) will be 13.3
amperes at 120 volts (domestic USA models).
13. Limit Switch
The limit switch is a safety switch and is mounted in the
heating element frame. It will open and break the circuit on
temperature rise in case the air flow through the heater
becomes low enough to cause the heater to overheat.
IV. TOOLS AND EQUIPMENT
In order to service the equipment covered by this Service
Manual, a technician will need all the common mechanics
tools such as wrenches, screwdrivers, hammers, etc.
In addition to the common mechanics tools, in order to do
refrigeration and electrical work, he will need special tools and
equipment such as:
1. Ammeter
2. Ohm Meter
3. Volt Meter
4. Refrigerant Recovery Equipment
5. Charging Cylinder
6. Vacuum Pump
7. Vacuum Gauge
8. Leak Detector
9. Brazing Equipment
10. Gauge Manifold
CAPACITOR
OHM METER
HIGH LOW
GROUNDED