There's two ways the alternator can stop working intermittently. If the battery light turns on and the alternator stops charging after the engine has been running a while, that is due to an intermittent problem inside the alternator, typically the voltage regulator, or a bad connection in the larger wire going from the back of the alternator to the battery. A bad connection will stop the alternator from charging but it may not turn the light on.
The other potential cause is a break in the wire between the battery light on the dash and the smaller wire plugged into the back of the alternator. Besides being the warning light circuit, that is the "turn-on" signal from the ignition switch that it's time for the voltage regulator to turn on and start running the alternator. Once the engine has started running and the alternator is turned on, that circuit can be thrown away and the system will continue to work until the engine stops running. An intermittent connection in that circuit will only cause the charging system to not start up and work. It will not cause a problem after it has started working. Also, if the "battery" light turns on, that proves that entire part of that circuit is working, so for all practical purposes that leaves the generator as the only logical suspect.
Also what happens on these cars is the PCM goes out and it cant control the alternator output so it shuts it down. Here is an alternator wiring diagrams o you can see how the system woks.
Here is the PCM location I would get a used one and plug it in to see what happens.
Check out the diagrams (Below)
Please let us know what you find.
Images (Click to enlarge)
Sunday, April 28th, 2013 AT 3:04 PM