Difference between revisions of "NG 900/9-3 Alternator"

Revision as of 01:24, 5 November 2009

Overview

Alternator brushes usually wear out first. Other common failures are voltage regulators, slip rings and eventually bearings. Brush kits are inexpensive, but hard to find for this alternator. New voltage regulators with brushes are available online. Rebuilt alternators cost more, but should have new bearings, slip rings, and other hardware. Saab dealers may charge more than the list price plus labor for a new OEM alternator that has never seen the inside of a Saab factory. Replacement cost can run as much as $800 at a dealer, compared to $300-400 at an independent mechanic or a chain service shop.

Remanufactured Units

I decided to go the remanufactured route. I found a 90-Amp alternator, rebuilt by Beck-Arnley on eBay. Fig. 1

Fig. 1 - Remanufactured Alternator

The alternator label reads: BOSCH 0 123 335 005 KC - 14V 45-90A 42 21 826

Alternator Pulley

My alternator came with the pulley, so I did not have to deal with the recessed 24-mm nut that holds it in place. Otherwise the pulley must be removed from the old alternator, and installed on the new one. Fig. 2

Fig. 2 - Alternator Pulley

Inspection

Removing Cover for Inspection

The cover is attached by three phillips screws and plastic snaps. To take it off, the nut at the positive terminal have to be removed, then the screws holding the cover. The plastic snaps are unlatched and the cover can then be pried up using a screwdriver. I decided to take a look. Fig. 3

Fig. 3 - Alternator with cover removed for inspection

Voltage Regulator

The regulator and brushes are one assembly, held in place by two long screws and washers. Replacing just this part seems like a good option if the bearings work. Fig. 4

Fig. 4 - Regulator on Alternator

Slip Rings

On close examination, the slip rings did not look new. The dark bands are the contact areas for the brushes, but the wear on the rings seemed minimal. The voltage regulator also did not look new, but new brushes had been installed in the regulator assembly. Fig. 5

Fig. 5 - Regulator removed and slip rings visible

Voltage Regulator Assembly

A new voltage regulator assembly consists of a ceramic carrier with spring-loaded brushes installed on one side and the voltage regulator on the other side. The contacts are crimped or soldered, and the voltage regulator appears riveted. Unlike the alternator, there is no core charge. Fig. 6

Fig. 6 - Voltage regulator assembly

Brushes

The Haynes manual specifies minimum brush length as 5 mm. The brushes are crimped or soldered in and can be replaced if you find a brush kit. The regulator seems to be attached to the ceramic holder by rivets and does not look easily removable. Fig. 7

Fig. 7 - Voltage regulator parts

Regulator label reads: BOSCH 1 197 311 214 EL 14V

References

• Haynes 5A-8.3-5
• Saab EPC 3A-0180

Part Numbers

• Regulator w. brushes #4737151
• Rebuilt alternator #AL0037X
• OEM alternator #5246871