View Single Post
Lorenfb Lorenfb is offline
Registered User
 
Lorenfb's Avatar
 
Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,352
Bosch alternators with an alternator light provide good diagnostic capabilities:

1. The light must be "on" with the key in the run position w/o engine started if not;
a. field winding is open or,
b. bulb is bad or,
c. brushes on regulator are bad or the regulator itself or,
d. slip rings are worn.

2. The light must be "off" when key is in "off" position if not then a shorted diode
in the alternator.

3. The light must go "off" when engine is started if not;
a. light glows dimly,
I. and does not get brighter at higher RPMs - poor connection from alt. to battery
II. light gets brighter at higher RPMs - an alt. diode is open or a field diode
is open
b. light glows brightly always - a shorted stator winding

Note: The gray type regulator (electronic) tends to be intermittent,
resulting in an overcharging condition (>14.7 is not good).
The old black ones (electro-mechanical) are the best.

Have Fun
Loren
'88 3.2
__________________
Have Fun
Loren
Systems Consulting
Automotive Electronics

'88 911 3.2
'04 GSXR1000
'01 Ducati 996
'03 BMW BCR - Gone
Old 01-06-2004, 05:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)