Isolating The Alternator; Direct Isolation Of The Alternator; Isolation Of Alternator By Means Of Switching-Off The Engine; Modifi Cations For Iveco Cursor With Nippon-Denso Alternator - Littelfuse 08096500 Series Manual

8.4.2 - Isolating the alternator

There are vehicles on the market that are equipped with alternators that cannot be directly de-energized
even though they have a D+ terminal on their casing, as the D+ terminal is not used as a supply point for the
voltage regulator.
In fact, the short-circuit of D+, or of its relative warning light, to earth can cause damage either to the alternator
(in particular to the regulator) or to the connecting wire which cannot support the short-circuit current.
Some types of alternators of this type are set out as follows:
MANUFACTURER MODEL
VALEO 14V – 60A
PARIS-RHONE 14V – 60A
VALEO 14V – 110A
VALEO 14V – 75A
VALEO 14V – 110A
BOSCH 28V – 55A
BOSCH 28V – 80A
In this case you can proceed as follows for the disconnection of the alternator:

8.4.2.1 - Direct isolation of the alternator

With the connection set out in Picture 9 (
the rest of the system when the TGC/E is de-activated. In this way the on-board electrical system remains
isolated both from the alternator and from the batteries.
It is necessary to use a supplementary power relay that has an NC contact equal to double the nominal
alternator output current (e.g. with an alternator of 55A, use a relay with an NA contact of 110A).

8.4.2.2 - Isolation of alternator by means of switching-off the engine

With this solution the switching-off of the engine is safely executed when the TGC/E goes into emergency
mode in vehicles equipped with EDC or electronic pump (not pneumatic).
As a consequence of the emergency operation, with the disconnection of the batteries and the switching-off
of the engine, the alternator's supply of electrical energy to the system is eliminated. Therefore no electrical
connection is actually made to the alternator.
In fact, the switching-off command issued by the TGC/E to the relay acts as if the command came from the
ignition key. The connections to be carried out is set out in Picture 10 (
supplementary relay must be used with an NC contact with suffi cient capacity to isolate the 15 key line to the
system.
8.4.3 - Modifi cations for IVECO Cursor with NIPPON-DENSO alternator
In these vehicles there exists the possibility of de-energizing the alternator by acting on its control logic; it is
actually necessary to insert an NC contact from an extra relay in the connection line between key 15 and the
alternator block, in accordance with the following connection diagram Picture 11 (

8.4.4 - Alternator maintenance

Zener diodes, which protect the system from dangerous overloads caused by the alternator, are used in some
newly designed alternators instead of normal rectifi er diodes.
In vehicles which have these alternators it is possible to eliminate the D+ connection or the brown wire to
maintain the alternator in operation during the disconnection of the batteries for special system requirements
during the emergency phase.
CODE APPLICATION (*)
NA205 RENAULT Express
AN13N137 RENAULT Express
A13VI73 FIAT Ducato 2.5 TDI
A11VI81 RENAULT Master
A13VI179 RENAULT Master
AN1 – 28V 10/55A SCANIA – MERCEDES
AN1 – 28V 10/80A SCANIA – MERCEDES
see the ending pages)
22
(*) The applications depend on
the type of vehicle and also on
its arrangement.
, carry out the isolation of B+ alternator from
see the ending pages)
see the ending pages)
in which a
.