Whatbs wrong with your FerrariQuiz 2

It's late one night...and you're driving home after a long ride through the country. As you get closer to your home, you notice that the dash lights are getting dim (OK...dimmer than they normally are)...and that the car just doesn't seem to run right. No warning lights are on, so maybe it's just your imagination??

The next morning the battery is dead. After a long slow charge...and load test, the battery test good. After all, it's one of those Optima batteries, and it's only a week old.

The next night...another long ride in the country and voila, the same scenario...dim lights and the car is dead the next day. Charge her up and take her to the nearest Pep Boys for some diagnostics.

The tests reveal:
-The battery is fine
-The alternator output is nil....and you need a new one.

So, a new alternator is installed...

Another ride in the country...another dead battery the next morning...and yet another trip to the Pep Boys.

Same diagnostics as before:
-Battery fine
-Alternator output zero
-They decide to check the electrical connections at the alternator and battery for cleanliness and mechanical integriry- All look good...and even you agree.

You drive the car home...and latter that evening, you decide to take her for a long, long test drive through the evening's full moon. This time you don't get home...The lights get dimmer and dimmer and eventually the engine just quits. Again, no warning lights to indicate any trouble, even when you get her to kick over once or twice before she goes completely dead. It appears as though, one again, the battery has died.

All of this seems very odd as we know:
-The battery test fine
-The alternator (we think) tests fine
-The connection to the battery and alternator are good

You call the flatbed...and she brings your car back to the house. Before you head off to bed, you put her on the charger, again!

The next morning, the battery tests fine...and she starts right up. This time you're nervous that the car will "leave you somewhere."

So, what's wrong with this car?

Regards,
David

Faulty wire from alternator to the battery......internally open within the insulation...can't see it......so connections look good. I am assuming you are testing the alternator output at the battery.

Alternator warning light out allowing no energization signal to the regulator?

This assumes when you replaced the regulator when you replaced the alternator since they are part of the same package.

What drewa said.

Geez,

You guys are too good...I thought this might be a tough question.
Alternator warning light out, hence no excitation voltage to the field=No alternator output.

(I did make the presumption that the regulator was internal to the alternator)

Appreciate your input!

Regards,
David

I learn something every day. Keep it up David!!!!

Well I knew the answer for a very simple reason - it happened to me on my 400.

I put a new alternator on it before I realised what the problem was, and even then I only found the cause by luck. I was sitting in the car puzzling on what could be wrong and noticed the warning light did not light up. Changed the bulb and hey presto!