Thermo King SB-190 30, Руководство пользователя

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Electrical Maintenance (Rev. 12/03)
33
13. Check the amperage in the 2A wire and record the read-
ing. Check the voltage at the B+ terminal and continue
to observe this voltage for a few seconds to see if it
increases, decreases, or stays the same. Note the change
in voltage and record the voltage reading.
Amperage in the 2A wire =____amps.
Voltage at the B+ terminals =___volts.
The voltage at the B+ terminal should be 13 to 18 volts
and the amperage in the 2A wire should be at least as
high as the rated output of the alternator.
NOTE: An alternator can easily exceed its rated out-
put. An alternator MUST at least reach its rated out-
put when full fielded. An alternator that has a
defective rectifier diode may reach 75% of its rated
output with a full field.
14. Stop the unit.
15. Use the readings obtained previously to determine the
problem by referring to the Diagnosis Chart.
NOTE: This assumes that the alternator did not
charge properly prior to the full field test.
Field Current Test (Checks the field windings,
brushes and slip rings)
Perform this test with the On/Off switch in the OFF
position.
1. Attach a clamp-on ammeter to the 2A wire near the B+
terminal on the alternator.
2. Connect a jumper wire between the F2 terminal on the
alternator and a chassis ground, and note the ammeter
reading.
3. The ammeter reading indicates field current. The fol-
lowing chart shows the field current for each alternator
with 12 volts applied to the field:
a. No field current or a low field current indicates an
open circuit or excessive resistance in the field
circuit. Replace the voltage regulator and brush
assembly, inspect the slip rings and repeat the test.
If the brushes are not the problem, replace the rotor
Alternator Rating
Field Current
@ 12 Volts
37 Amp 3.5 to 4.5 Amps
65 Amp (optional) 4.0 to 5.0 Amps
Diagnosis Chart
Amperage in 2A Voltage at B+ Problem/Solution
At or above rated output At or above battery voltage and
increasing Voltage regulator defective / Replace volt-
age regulator and brush assembly
Approximately 60% of
rated output Approximately equal to battery voltage
and does not change, or rises slightly Rectifier diode defective / Repair or replace
alternator
Low or no output Less than or equal to battery voltage
and decreasing Stator windings, field windings, brush or
diode defective / Perform Field Current Test
to check brushes and field coil, or replace
alternator