Carrier 69NT40-541-306, Операция и обслуживание

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T-354 7–26
7.17 EVAPORATOR FAN MOTOR CAPACITORS
The evaporator fan motors are of the permanent-split capacitor type. The motor is equipped with one capacitor
used in the high speed circuit, and another capacitor is used for the low speed circuit.
7.17.1 When To Check For a Defective Capacitor
• Fan motor will not change speed. For example: in the conventional perishable mode, the motors should run
in high speed. In the economy perishable mode they should switch speeds and in the frozen mode, the mo
tors should run in low speed.
NOTE
The evaporator fan motors will always start in high speed.
• Motor running in wrong direction (after checking for correct wiring application).
• Motor will not start and IP-EMs are not open.
7.17.2 Removing the Capacitor
WARNING
!
Make sure power to the unit is OFF and power plug disconnected before servicing capacitor(s).
WARNING
!
With power OFF discharge the capacitor before disconnecting the circuit wiring.
Capacitors must be discharged properly before testing. To discharge the capacitor, first turn the unit power OFF
and disconnect the unit power plug. Then place a 20,000 ohm, 2 watt resistor across the terminals of the capacitor
for approximately 30 seconds.
The capacitors are located on the motor and may be removed by two methods:
1. If container is empty , open upper rear panel of the unit.
2. If container is full, turn the unit power OFF and dis connect power plug. Remove the evaporator fan motor
access panel (see Figure 3.2 ). For removal of the evaporator fan assembly, refer to Section 7.16
7.17.3 Checking the Capacitor
If the capacitor is suspected of malfunction, you may choose to simply replace it. Direct replacement requires a
capacitor of the same value. Two methods for checking capacitor function are:
• Volt-ohmmeter set on RX 10,000 ohms.
Connect ohmmeter leads across the capacitor terminals and observe the meter needle. If the capacitor is
good, the needle will make a rapid swing toward zero resistance and then gradually swing back toward a
very high resistance reading.
If the capacitor has failed open, the ohmmeter needle will not move when the meter probes touch the ter-
minals. If the capacitor is shorted, the needle will swing to zero resistance position and stay there.
• Capacitor analyzer:
The function of the analyzer is to read the microfarad value of a capacitor and to detect insulation break-
down under load conditions. The important advantages of an analyzer are its ability to locate capacitors
that have either failed to hold their microfarad ratings or those that are breaking down internally during
operation. It is also useful in identifying capacitors when their microfarad rating marks have become
unreadable.
7.18 EVAPORATOR SECTION CLEANING
Containers and Container units that are exposed to certain fumigants may develop visible surface corrosion. This
corrosion will show up as a white powder found on the inside of the container and on the reefer unit evaporator sta-
tor and fan deck.