360 Weird Alternator Light Behavior

Hi all.
I went out with the 360 for a two days trip, something around 400 kilometers in total.

Today, while driving home on the highway, the battery red light light came on INTERMITTENTLY.

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This, according to the Owners Manual, is a warning of an overcharging alternator:

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My battery (Bosch S5) is just 3 months old.
These were the electrical loads I had at the moment:
- Headlights
- Air Conditionig
- Stereo

I switched off the headlights and after something around 30 secs to one minute the Battery Light went off.
I switched the headlights on again and after more or less the same time the light came on again.

Leaving the headlights on I did the same test with the Air Conditioning and I got exactly the same results.

Being daytime and quite hot I drove home with A/C on leaving off the headlights and the Battery Light stayed off for the whole trip.

Now... isn't it a very weird behavior? I mean, I would expect this from an alternator that is not charging enough, not from one that is overcharging.

And how on earth if it was actually overcharging, It reduced the output power switching off a medium/heavy load like headlights or A/C?

Looking for any kind of help, ideas, etc... thank you!

 

Your tests are meaningless unless you measure the voltage directly off the battery terminal with a multimeter. Typically on idle, the battery voltage should be above 13 volt. With load, the alternator will kick in to maintain an above 13 volt reading.

 

Yeah well I know how to test an alternator and tomorrow I will do it.
What I don't understand is the overcharging warning coming on while loaded and disappearing when lowering significantly the load.
This is what I would expect from an undercharging alternator...

 

You might want to read up on this thread: https://www.ferrarichat.com/forum/threads/2004-360-alternator-light-on.562958/#post-145639993

 

Ok some news.
15 Amp fuse on the voltage sensing line connected to the battery is ok.

I didn't check now the alternator connections, but I did a major service 2 months ago and everything was absolutely fine underneath the car.

I'm the second owner , but I'm quite comfortable saying that my car maybe was never driven in the wet, because there is no corrosion at all, all the electrical connections are in very good shape. Also the ground point near the left engine mount is in perfect conditions.

Clarified that, I tested the alternator as best as I could, using a digital multimeter hard wired to the battery terminals:

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With the car off I get 12.7 V, that is good.

As soon as I start the car I get 13.9 and after about one minute it stabilizes around 14-14.2 V with no load. This seems a little bit weak but I would say ok.

Then with A/C on with fan at max speed, headlights and stereo I got around 13.6-13.7. All this with a cold car, just after start up.

At that point I started to drive the car normally, heading to the nearest highway, still with A/C headlights and stereo on.

Quite soon the Voltage reading started to drop, I would say the more the car warmed up, the more the voltage dropped.

And voilà, cruising on the highway in 6th gear between 3 to 4000 rpms I had again the red battery light flashing on the dashboard.
This was the reading when it started to flash:

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So, being this I would say that my alternator is quite weak and when it warms up is not able anymore to keep up with the requested load. Do you guys agree on that?
In other words is UNDERCHARGING.

But said so, why on earth with 12.6 Volts I got a flashing battery light that according to both the user and service manual is an OVERCHARGING warning?

This doesn't make any sense to me.

Anyway, I switched the headlights off, the reading came up a little bit around 12.8 and after a few seconds the blinking light went off.
Headlights on again and Battery Light flashing again. Same results trying to switch on and off the A/C leaving the headlights on.

What do you think?

 

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My interpretation from the owner manual is that the alternator light flashing indicate that there is a problem with the charging system. It could be under or overcharged, not one state or the other. The problem seems to be a weak alternator when running hot. Perhaps the voltage regulator is about to go?

 

When mine did this, it was the alternator lead....
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First check the wiring by doing a voltage drop test. Positive lead of Multi-meter to battery positive post and negative lead to battery post of alternator with engine running and loads on. No more than .5V drop. Now place positive lead of DMM to case of alternator and negative lead to engine ground near left motor mount. No more than .3V drop with engine running. If wiring good than alternator is suspect. If you have leads switched during process no worries you will just have a negative number which is still accurate.

 

More then likely it's the main battery cable that goes to the alternator. As the picture above shows. The hotter the car gets, the higher the resistance in the cable.

It's a bit of a bigger to change as it travels under the intake manifold. The cable has been updated by ferrari a couple of times for this reason.

 

@MerlinTech Thoughts?

 

Didn't know about this, by mine is a very late car (July 2004) so I think it should have the latest update.
Any more info on this?

 

Have you removed the battery and done a load test on it? Most shops selling batteries do this for free. I would verify this before going after the alternator. Sometimes batteries fail internally when loaded.

 

No I didn't because actually my battery is only 3 months old.
Would it still be a good test to do anyway?

 

Yes, I would. They fully charge it and then put a load on it to ensure it is per its rating (capacity).
Brand new batteries fail as well. If it passes then that can be removed from your trouble shooting guide.

 

First check the wiring. Very common for the power wire on the alternator to degrade and need a new end. Then you can see if the alternator is actually putting out under load as it should. May need an alternator as well.

 

As others have said, Ferrari released a tech bulletin regarding replacement of the cable from the alternator output terminal to the main junction block. The end of the original cable has a poor internal connection that leads to high resistance, excessive heat which causes destruction of the insulation and corrosion of the cable. You can measure the output of the alternator right at the output terminal and also do a voltage drop test across the output cable from the output terminal to the main power junction block under the cover behind the left seat. You may also have a issue with the alternator itself which should be tested when the output voltage is low.

 

Common problem on 360. The main cable from the alternator will overtime get cooked by the exhaust manifold being to close to the cable. Ferrari did not put a heat shield between them. The cable as it heats up turns into a resistor. Need to replace the burned part of the cable and install a heat shield between the alternator and exhaust manifold. I had the same problem on my 03 360.

 

Just a technical note if it may help anyone. The heat does not increase the resistance of a copper cable in any meaningful way. Its very negligible in this case.
There is most likely a mechanical problem with the way the lug is crimped onto the cable, materials, or moisture got into the lug/cable interface causing corrosion. High heat will accelerate the corrosion. Tin/copper also seems to corrode without the presence of moisture under high heat. If the joint is air tight this corrosion should not happen.
If it were me I would have a new cable made using compression lugs (Crimped with the correct hydraulic tool) and epoxy to seal the insulation to the lug for a waterproof assembly. That and a heat shield.

 

Ok guys finally I tested the voltage drop.

First of all this is my alternator connection from two different angles (plastic cap removed):

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I would say it looks in perfect conditions..

And now the voltage drop.
This is between the alternator output and the positive cable terminal behind the driver seat:

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And this between the alternator output and the positive terminal on the battery:

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I would say they are pretty much ok... am I right? What do you think?

 

Kind of hard to figure out your meter, as it has no decimal point on the display. It looks lkie you have it on a 2000 Milivolt scale, but the meter only shows 3 digit, which is kind of weird. So your reading is either 49 Milivolts ( 0.049 Volts) which would be extremely low or 490 Milivolts (0.490 Volts, roughly half a Volt), which is a little on the high side. You should have maybe .1V drop across that length of wire.

Did you do this test under load, with the engine running, the charging system working and some load on the circuit (headlights on, A/C on)? If the test was performed with the engine not running and the alternator charging, then it is not a valid test.

You are going to have to figure out your meter reading and determine what it is. Might be better if you used the 2V scale. Good automotive Fluke meters auto-range on the scale, and you can always tell what the reading is, because its in volts. The decimal point just moves around as the range of the meter changes.

 

I meant to say use the 20V scale. You can also check the voltage of a good 1.5v AA cell to see what the reading is on the 2000Mv scale in order to determine what your reading means.

 

This (sorry for the unprofessional background ) is the voltage reading on a brand new 1.5 battery:

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So the voltage drop was, as I correctly interpreted, 0,049 Volts.
Yes, the engine was running

 

With that low a voltage drop, there is almost no resistance in the cables and connections all the way from the alternator to the battery. Everything on the positive side is in perfect condition. Don't forget the negative side. Test the voltage drop from the case of the alternator to the negative side of the battery to see if there excessive resistance.
If the negative side checks out, I would say that you have a problem with your alternator. You could have an alternator shop test it off of the car to see if it has intermittent output. It may only have the issue once it gets hot, so that might be hard to duplicate. You could have a good shop rebuild your original for a fraction of the cost of a new alternator.

 

Yeah I forgot to mention that, I checked the negative side as well.
I had more or less the same readings.. actually even a little bit lower.