Usage:
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 characteristics of each of the different terminal patterns and use this information as an aid to servicing alternators.
There are four illustrations of terminal locations for the 6N9294 (35 Ampere) and the 5S9088 (50 Ampere) Alternators. These are shown in Illustrations 1 through 4.
Illustration 1. Bosch 6N9294 (35 Amp) and 5S9088 (50 Amp) Alternator.
Illustration 2. Nippondenso 6N9294 (35 Amp) and 5S9088 (50 Amp) Alternator.
Illustration 3. Delco-Remy, 35 Amp, 6N9294 Alternator.
Illustration 4. Delco-Remy, 50 Amp, 5S9088 Alternator.
Bosch®, Nippondenso®, 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 the Nippondenso and Delco-Remy alternators and the "D+" terminal on the Bosch alternator. Also, the "R" terminal on all of the examples may be used as an auxiliary terminal; for example, to power a tachometer.
The Motorola® alternators shown in Illustration 5 are used primarily in truck, industrial and marine engine applications.
Illustration 5. Motorola alternator.
The two main terminals in this example are the positive output and negative output. The stator terminals would be used to power a tachometer.
The following chart details the part number, application, and specifications for the Motorola alternators.
Dimensions for terminal mounting studs and screws may vary between alternators. However, vehicle electrical wiring will allow for the differences, so all alternators will work with any Caterpillar engine.