Service Manual

Alternator ISB, ISBe and QSB (Common Rail [...]
Page 13-10 Section 13 - Electrical Equipment - Group 13
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Typical Delco™ Alternator Wiring System
The main function of the indicator (I) terminal is to indicate if the alternator is working correctly. Typically, an indicator
light is wired to this terminal. If the alternator is not charging properly, the light turns on. Another function of the
indicator (I) terminal is that it can be used to supply up to 1 ampere of output at system voltage.
Relay (R) Terminal
The function of the relay (R) terminal varies. It can supply up to 4 amperes of output at one-half nominal alternator
voltage to power items such as a tachometer or an hour meter.
One-Wire System
This is the simplest of the wiring systems because the only wires connected to the alternator are at the battery (BAT)
and ground terminals. (See Table 5.) Connecting to the R terminal and I terminal is optional.
Three-Wire System
This system requires more wiring because it has a battery (BAT) terminal, R terminal, two blade terminals identified as
number 1 and number 2, and a ground terminal. Typically, in the three-wire system, the number 1 blade terminal
serves as the I terminal. (See Table 5.) The advantage of the three-wire system is that it provides the same features
as the one-wire system, plus remote sense. By connecting the number 2 blade terminal to the battery's positive (+)
terminal, the voltage is both sensed and regulated at the battery instead of the alternator. This eliminates the potential
for voltage losses in the wiring from the alternator to the battery.
Table 5, Typical Alternator (Delco-Remy™)
Key Terminal Connected To
5 BAT Battery
3 GRD* Ground
4 R* Charge indicator, automatic lockout
system, tachometer**
1 Blade number 1* Indicator light
2 Blade number 2 Voltage sense
6 I* Indicator light
*Not all alternators have this feature.
**Provides voltage pulses at about one-half system voltage at a frequency of one-tenth of the alternator rpm.