Fusible link melted!
First thing to do is get a lamp in series with the ground lead of the battery. This will show if the system is drawing current.
Then make SURE EVERYTHING is shut off, check the trunk light, dome light, glove box, ANYTHING, and yank out the cigarette lighter.
Next pull out ALL the fuses
Then jumper around the fuse link. Smart way to do this, until you find the problem, is buy an inline fuse holder and get some 20A fuses
(You'll have to jumper the fuse link to do any testing)
With everything above unhooked, and the light still comes on as Steve says, unhook the main alternator wire.
From there it's a matter of unhooking stuff until you find the problem
Look at the simplified MAD diagram, which represents the "main feed" from the battery, through the bulkhead, and back to the alternator
Look at the diagram below. The battery main feed is represented by the red wire, through the fuse link, through the ammeter, and back out the bulkhead to the alternator
NOTICE the "welded splice". This is a factory splice under the dash, taped up in the harness. You can examine it by untaping from the ammeter, following the black ammeter wire until you get to the splice
This splice supplies UNFUSED power to
the ignition switch
the fuse panel "hot" buss"
the main headlight power (breaker in / on the switch)
the wiper switch on at least some models (breaker on/ in the wiper switch)
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
Also SUSPECT that other wires IN the harness have melted/ welded together. It would be a WISE idea to unwrap the underhood harness if there's evidence that this "came from" the alternator, and certainly do the same with the under -- dash harness
IF you have made changes to the wiring, suspect those. As I said, the ignition feed is NOT fused, is ONLY protected by the fuse link, which will NOT protect the smaller size ignition wires. So if you've added a tach, or changed the ignition system, check that out carefully
First thing to do is get a lamp in series with the ground lead of the battery. This will show if the system is drawing current.
Then make SURE EVERYTHING is shut off, check the trunk light, dome light, glove box, ANYTHING, and yank out the cigarette lighter.
Next pull out ALL the fuses
Then jumper around the fuse link. Smart way to do this, until you find the problem, is buy an inline fuse holder and get some 20A fuses
(You'll have to jumper the fuse link to do any testing)
With everything above unhooked, and the light still comes on as Steve says, unhook the main alternator wire.
From there it's a matter of unhooking stuff until you find the problem
Look at the simplified MAD diagram, which represents the "main feed" from the battery, through the bulkhead, and back to the alternator
Look at the diagram below. The battery main feed is represented by the red wire, through the fuse link, through the ammeter, and back out the bulkhead to the alternator
NOTICE the "welded splice". This is a factory splice under the dash, taped up in the harness. You can examine it by untaping from the ammeter, following the black ammeter wire until you get to the splice
This splice supplies UNFUSED power to
the ignition switch
the fuse panel "hot" buss"
the main headlight power (breaker in / on the switch)
the wiper switch on at least some models (breaker on/ in the wiper switch)
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
Also SUSPECT that other wires IN the harness have melted/ welded together. It would be a WISE idea to unwrap the underhood harness if there's evidence that this "came from" the alternator, and certainly do the same with the under -- dash harness
IF you have made changes to the wiring, suspect those. As I said, the ignition feed is NOT fused, is ONLY protected by the fuse link, which will NOT protect the smaller size ignition wires. So if you've added a tach, or changed the ignition system, check that out carefully