Operating instructions

TM 11574A-OI
3-27
(13) Evaporator Fan Motor Capacitor
Units are equipped with single permanent –split capacitor fan motors.
(a) When to Check for a Defective Capacitor.
1
When the 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 motors should run in
low speed.
NOTE
Units are equipped with single permanent-split capacitor fan motors. The evaporator fan
motors will always start in high speed.
2
Motor running in wrong direction (after checking for correct wiring application).
3
Motor will not start and IP-EM’s are not open.
(b) Removing the Capacitor. To remove the evaporator fan motor capacitor, perform the
following steps:
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 disconnect power plug. Remove the
evaporator fan motor access panel (Figure 2-1). For removal of the evaporator fan
assembly, refer to section 3-10b(12).
(c) Checking the Evaporator Fan Motor 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:
1
Volt-ohmmeter set on RX 10,000 ohms.
a.
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.
b.
If the capacitor has failed open, the ohmmeter needle will not move when the
meter probes touch the terminals. If the capacitor is shorted, the needle will
swing to zero resistance position and stay there.