5 - The alternator has a higher ampere rating. Performance is superior to that of the standard system at speeds of
rotation above 1500 rev/min; at lower speeds the performance of the two systems remains identical.
The alternator is equipped with a solid state regulator that replaces the printed circuit board (the electronic control unit
in the standard two speed system.)
The regulator includes an electronic circuit by which the voltage component of the current output is limited to a maximum
value of 48 Vdc .
6 - Power supply: There are two power lines to the alternator, protected by 15 amp and 30 amp fuses located in the
tractor fuse box.
CAUTIONS: to ensure smooth operation, all wiring connections forming part of the cab heating system must be secure,
clean, and free from any traces of rust.
Loose connections or oxidation on surfaces will significantly reduce the effectiveness of the heating system.
The heating alternator drive belt must always be correctly tensioned, to ensure that the alternator receives a steady
input horsepower of 4.5HP approx.
Checks must be carried out employing suitable instruments; the use of makeshift contrivances such as indicator lights
with leads and clips is to be avoided, as these can cause serious damage to the system.
FAULT DIAGNOSIS
PROCEED AS FOLLOWS:
(The positions of the on-off and fan control switches indicated here refer to the illustrations on page 357)
1 - With the ignition key in the ON position (engine at standstill) and the heater and fan control switch at position 1, the on-off
switch indicator should be alight, the fan in operation and a flow of warm air established. If not, check the wiring and
connections between the controls and the fuse box (wires connected to the 15 A fuse), and inspect the fuse itself.
If the fuse and the connections are found to be in good order, apply a voltmeter to the 6-pin connector near the fuse
box, connecting the “+” prod to terminal 5 (red - 2,5 power) and the “-” prod to terminal 4 (2 black leads - 1, 5), as
indicated in Fig 4. The meter should give a reading of 12 V if the contacts are healthy. If not, other parts of the system
need checking.
Again with the ignition key in the the ON position (engine at standstill) and the heater and fan control switch at position
1, apply the voltmeter to the terminals of the first and second relays (see fig 4) and check that the reading is 12 V. Now
turn the ignition key to the OFF position and disconnect the wiring contacts of the heater switch. With this same switch
at position 1, check with the tester that it passes current and is therefore operating efficiently. This done, reinstate the
contacts.
systems
air conditioning
86
8
358
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