2004 360 Alternator light on

Make sure that the voltage sense wire is connected on the positive battery terminal.

 

...there is also an inline fuse on the voltage sense wire.

 

Was the rebuilt alternator bench-tested under load? The alternator has to be tested under load because if any of the rectifier diodes are blown, it might show good voltage, but sag under load.

The main alternator connection is a known failure point in the 360. Does the main lug and wiring at the alternator show any sign of corrosion, fraying, or insulation/cable damage? Does the ground connection look clean?

What voltage is the alternator putting out with the engine running as measured at the battery terminals?

If anything less than 13.8 volts at the battery terminals, check the voltage at the positive terminal behind the driver's seat. If it's the same as at the battery, the alternator is probably defective. Could be a bad regulator, blown rectifier diodes, worn brushes, or damaged windings.

If it's showing more than 15 volts, check the battery voltage sense wire/fuse.

 

Check that all earths are clean also

 

I had the same problem with my 2002 Modena 360 manual gearbox !!

I drove 580 km (about 400 miles) to a Ferrari club track event in speeds in excess of 230 km/h (about 140 mph) and the alternator light came on...
Later the light came out...
I drove 2 sessions of 4 laps at the race track and the alternation light came on and stayed on...

There were 2 Ferrari mechanics that checked my car and told me about the alternator problem..

They told that "if you try to drive your car back home, you won't make it past 5 km / 10 minutes... Your car will die !!"

So they rushed to their shop and found a used Ferrari alternator...

First they said that it is usually the regulator circuit that goes bad due to heat..

So they replaced that, the light came out, but they measured the voltage and it was still low , just 12.8 V instead of normal of 13.8 V or above...

So at the pits of the race track, they replaced the alternator and voila, it worked just fine !! 14.2 V and everything fine !!

I drove back home no problem !!

So, if you cannot rebuilt it, just buy a new one !!

 

Had my battery light appear when tracking my 360 the other day...only when pushing it at the end of the straights it seems. After owning the car for 6-7 years now I am on my 3 alternator!!!!( last one I changed) Yes all the common faults like ground points etc have been checked each time- and no signs of failure there. Battery new 6 weeks ago and car always on the tender when not in use. Appreciate your input...thanx.

 

Oh goodie, another weak link to learn about. Proceed.

 

Steve, are you referring to Fuse #74 (for my own education)?

 

It's 18D:

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Thanks. I have to write this down because recently I'm forgetting a lot of stuff.

 

....got my alternator out- had it tested- no problemo- now the search for solutions continues.

 

hi can you tell me where is the fuse for the exciter wire

 

The only fuse for the alternator is near the battery

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Alternator harness plug viewed from contact side (not wire side)

I couldn't find any photos of the fuse.

 

the relay that excites the alternator (behind drivers seat) only has power while cranking, there is no other terminal in this relay 90 that would energize the alternator. any suggestions? Thank you ahead of time

 

Check your Owners Manual for the correct relay. The relay number varies from car to car. Possibly relay 85 on earlier cars (or Euro cars?).

Whatever the car, it's located here (shown in red)

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Here's a wiring diagram which may help

https://www.dropbox.com/t/LMQwdv956zgLdMS8

The alternater is at the bottom of the page marked "28S 27S"

If possible, check for 12volts at the alternator on pin 3 (ignition off) and 12 volts at on pin 2 (ignition on).

 

Thank you my friend!