Thermo King T-1000R, Maintenance Manual

Page: 123 / 282

Electrical Maintenance 8-3
Interface Board Fuse F4
The interface board has a 300 ohm resistor and a resistor bypass fuse (F4) in the alternator excitation circuit. The fuse and
resistor are connected in parallel and are located on the interface board. Removing the resistor bypass fuse places the 300 ohm
resistor in the excitation circuit as required for Thermo King alternators (and Australian Bosch alternators). Installing the resistor
bypass fuse removes the 300 ohm resistor from the excitation circuit as required for Prestolite alternators. See the specific unit
wiring diagram for exact details.
NOTE: The F4 fuse must be removed from the interface board on units equipped with Thermo King alternators. The voltage
regulator on the Thermo King alternators will be damaged if the unit is turned On with the F4 fuse in place on the interface
board.
Test Equipment for Checking Voltage and Current
Always use accurate test equipment when checking alternator circuit voltage and amperage, but be sure voltages are measured
from the designated terminal to the alternator chassis ground. All voltages are DC voltages unless otherwise noted.
Alternator Load Test
Thermo King no longer recommends a full field test for determining the alternator current output. Full fielding an alternator
can cause increases in alternator output voltage that may damage internal alternator or unit components. This damage may not
be readily apparent.
To test the alternator under load, Thermo King recommends the use of a clamp-on ammeter to monitor output current, both
on initial startup and under full unit load conditions. For example, on multi-temp units, all remote evaporators should be turned
on.
General Diagnostic and Warranty Evaluation Procedure
Complete the following diagnostic procedures before replacing an alternator or the voltage regulator.
1. When testing an alternator, use accurate test equipment
2. Make sure the drive belts and pulleys of the charging system are in good condition and are adjusted properly before testing
the alternator. Be sure the pulleys are the correct size. Worn belts, loose belts and worn or improperly sized pulleys will lower
the output of the alternator.
3. The battery must be charged and in good condition, the battery cable connections must be clean and tight, and the 2A, SENSE
(sense), and EXC (excitation) circuits must be connected properly. All charging circuit connections must be clean and secure.
If the unit battery is questionable, a known good jumper battery should be substituted for alternator testing.
NOTE: If the unit battery is questionable, a known good jumper battery should be substituted for alternator testing.
NOTE: Do not perform this test with a battery charger connected to the unit battery.
NOTE: All voltage readings should be taken between the chassis ground on the alternator and the terminals indicated, unless
stated otherwise.
4. Check that the resistor bypass fuse (F4) has been removed. Units with Thermo King alternators must have the resistor bypass
fuse (F4) removed.