1998/12/07 Caterpillar

All Caterpillar Engines

This article identifies the external terminal locations on alternators that are supplied by various manufacturers and used with Caterpillar engines. Note the characteristic of each of the different terminal patterns in the illustrations provided and use this information as an aid to servicing alternators.

Illustration 1.
Bosch 7N-9720, 9G-9538 and 100-5046 Alternators.

(1) B+ terminal.

(2) D+ terminal.

(3) B- terminal.

(4) R terminal.

Illustration 2.
Bosch 9W-3043 Alternator.

(1) B+ terminal.

(2) D+ terminal.

(3) R terminal.

(4) B- terminal.

Illustration 3.
Delco-Remy 155-7434 Alternator.

(1) B- terminal.

(2) B+ terminal.

(3) R terminal.

(4) Indicator light terminal.

Illustration 4.
Delco-Remy 3E-7892, 3E-7578, 3E-7577 and 112-5041 Alternators.

(1) Top view.

(2) B- terminal.

(3) B+ terminal.

(4) R terminal.

Illustration 5.
Delco-Remy 8C-6163, 4N-3986, 4N-3987, 9X-7803 and 114-2401 Alternators.

(1) B- terminal.

(2) B+ terminal.

Illustration 6.
Delco-Remy 3T-6352, 5N-5692 and 7G-7889 /qm/ Alternators.

(1) B+ terminal.

(2) R terminal.

(3) B- terminal.

Illustration 7.
Delco-Remy 9X-6796, 107-7977, 117-1379, 121-4134, 121-4135, 125-9597 and 132-2156 Alternators.

(1) Optional warning light terminal.

(2) B+ terminal.

(3) R terminal.

(4) B- terminal.

Illustration 8.
Delco-Remy 8C-5510 Alternator.

(1) B+ terminal.

(2) Phase tap (P).

(3) Lamp (L).

(4) Ignition (I).

(5) External sense (S).

Illustration 9.
Denso 9G-4574, 6T-7223 and 100-5045 Alternators.

(1) B+ terminal.

(2) R terminal.

(3) B- terminal.

Illustration 10.
Denso 3E-7772, 105-2811, 105-2812, 105-2813, 105-2814 and 105-3132 Alternators.

(1) R terminal.

(2) Ignition.

(3) Indicator lamp.

(4) B+ terminal.

Illustration 11.
Motorola/Prestolite 2P-1204 Alternator.

(1) B- terminal.

(2) B+ terminal.

Illustration 12.
Motorola/Prestolite 107-2519 and 112-8032 Alternators.

(1) B+ terminal.

(2) B- terminal.

(3, 4) R terminal is an AC tap from the Stator.

Illustration 13.
Motorola/Prestolite 149-2064 Alternator.

(1) D+ terminal.

(2) B+ terminal.

(3) B- terminal.

(4) R terminal.

Illustration 14.
Motorola/Prestolite 6T-1395, 6T-1396, 7T-2095 and 7T-2096 Alternators.

(1, 4) R terminal is an AC tap from the Stator.

(2) B+ terminal.

(3) B- terminal.

Bosch, Denso (brushless), and Delco-Remy alternators contain three main external terminals: positive output, negative output and "R" terminals. Output for battery charging and for electrical accessories is taken from the positive terminal. The negative terminal is connected to ground. On many machines, the Electronic Monitoring System (EMS) is connected to the "R" terminal.

In some instances, an external power source is required to restore the residual magnetic field in the alternator. An explanation is in Service Magazine, July 7, 1986, "Brushless Alternators May Not Charge In Certain Conditions". This is accomplished by using the "R" terminal on Denso (brushless) and Delco-Remy and the D+ terminal on the Bosch alternator. Also, the "R" terminal may be used as an auxiliary terminal; for example, to power a tachometer.

The Motorola/Prestolite alternators shown in Illustration 14 are used primarily in truck, industrial and marine engine applications.