Service manual

16
Problem
5. Compressor trips breaker or thermal current
overload.
Compressor trips circuit breaker or thermal current overload
immediately (no hum). Note that this problem is different
from the previous one in that in the previous problem, the
compressor did hum for several seconds.
With the selector switch in “Fan Only” position, the fan
works OK.
Question: “What are the possible causes?”
Answer:
1. “The compressor winding is shorted or grounded,
or”
2. “The circuit breaker or thermal current overload is
weak, (this rarely occurs, but it can occur after the
switch has tripped out many times. The only repair
is to replace the circuit breaker or overload).”
Question: “How do I repair it?”
Answer:
1. “With the power turned off, check the resistance
between all three compressor terminals and ground.
If any continuity is found, locate the ground and
correct it.”
2. “Check compressor windings per instructions (See
page 8).”
3. “If the above checks are OK, replace the switch that
is tripping out.”
Problem
6. Compressor makes loud growling noise.
Customer has turned the unit off and called for service
because he believes the air conditioner is surely burning up
since it makes such a loud noise. On inspection, we find that
the compressor starts but draws high current and continues to
make the growling noise until the thermal current overload
trips out.
Question: “Which components can we determine are
working OK from the symptoms?”
Answer:
1. “The power is getting to the compressor.”
2. “The start circuit is starting the compressor OK.”
3. “The capacitors and relay are providing the starting
torque.”
Question: “Then why the noise?”
Answer: “The start capacitor is staying in the circuit
and the compressor is running with too much
capacitance. This condition is caused by; 1)
the compressor does not come up to speed
and does not supply adequate voltage to
actuate the potential relay, or 2) the potential
relay contacts are welded shut, or 3) the
potential relay coil is open.”
Question: “How do I repair it?”
Answer:
1. “Check the voltage between “C” and “R” terminals of
the compressor. Low voltage can cause the
compressor to not come up to speed.”
2. “Check out the potential relay with hermetic analyzer
or try a new potential relay.”
3. “Check compressor windings per instructions.”
Problem
7. Fan Vibration.
The customer complains that the unit vibrates excessively. We
turn selector switch to fan/low or fan/high and the vibrations
are not appreciably reduced (we quickly eliminate the
compressor as the source of vibration).
The fan motor and fans were carefully balanced at the factory,
but they are fragile enough that they can be bent by rough
handling.
Question: “How can I determine which part of the fan
assembly is causing the vibration?”
Answer: “By removing the fan wheels one at a time
and running it each time until the vibration
stops. To correct the problem, replace the
faulty part.”
Problem
8. Fan won’t run.