As most know, the Mondial has had a reputation of having weird electrical things. And, as has been documented, often time the weird behaviors start mysteriously, and then are mysteriously cured by a new battery or fresh charge, even with a working charge system.
Here is the history of Mondial alternators and batteries:
M8: Bosch 65A alternator and 66Ah battery
QV: Bosch 80A alternator and 66 Ah battery
3.2: Bosch 85A alternator and 66 Ah battery
t: Delco 105A alternator and 66-70 Ah battery (same as 348)
911 3.2: 92A alternator and 66Ah battery
911 3.4: 115A alternator and 72 Ah battery
So, what I think may be happening is a circuit load/battery/alternator mismatch. The electrical load is NOT that different between Mondials, and notice they kept going up every year while the real 'requirement' was about the same; Also, the drive train was engineered for the 2 seat 308/328 as well, with a bit lessor load potential Especially if a more powerful battery and/or stereo amplifier is installed, it may accentuate the condition.
Ergo, I think a basic solution to some of the Mondials weird electrical behavior may be solved by going to a bigger alternator and/or battery to better meet load requirements.
So, anyone have advice or a suggested a higher output replacement alternator and how to wire it up? I know the alternator is easy to get to through the starboard rear wheelwell.
One thing I believe is that when the Alts get wet they tend to go south shortly thereafter.
All the later Model Alts you mention are interchangeable up to the Mondial T, which is different.....and one giant source of problems is the Connections at the FUSE BOARD (the 2 Fat Red Wires with the phony rubber coating) , and the Relays under the AC Center Console!
Ok, if you're like me, you're wondering exactly why doesn't the alternator that came with my car work right. Most 308/Mondial came stock with the one wire alternator setup. That is, a heavy battery wire and the idiot light wire. This system creates current through the residual magnetism left in the alternator. This means that it has to spin in order for the voltage regulator to turn on. After it's on, it makes voltage until it reaches 12V-14V. It senses this voltage at the unit itself and self regulates based on it's own immediate output of 12-14V. The problem with this alternator is where the voltage regulator gets it's reference voltage to regulate itself, it basically tells itself to keep producing 12V-14V because it senses it's output--
Lost yet? So what's wrong with this system?
The problem is that after you start adding resistence such as lights, power windows, battery charging the voltage begins to drop. A good example is a row of lights...if you hooked up lights in DC series circuit, you would notice that when you look down the string of lights, the first one is much, much brighter than the last one.
This is called "line loss" or "voltage drop" by the time you take a voltage reading down the line from the Alternator you getting 10V instead of 14V which is what you should be reading anywhere in the system. This is because the Alternator is reading 12V from itself before these "resistive loads" and is perfectly happy. This explains why the windows and sunroofs usually move sooooo slow.
What they should have put in is a Three-wire alternator. The significant difference with this alternator is the Voltage Regulator, it requires a remote voltage sensing wire. This wire is also used to "flash" the field so you no longer need that "residual voltage" which means that the speed of the alternator is now insignificant in relation to voltage output.
Let me explain;
Remember when I said the 1-wire kept reading it's own immediate output and continued to regulate that output? Well a three wire requires a wire hooked up to an ignition hot wire, hopefully one that has a low voltage, The perfect wire would be the last wire after all the "resistive loads"
Remember that string of lights I was talking about? It would be like hooking it up to the last light.
These low volt wires are easily found in the outdated fuse box in most mondials/308's. What happens with this magical remote sensing is that the Alternator will sense 10V and adjust the voltage regulator accordingly to ensure that it's remote sensing wire has the required 14V.
Let me explain in easier terms;
1-wire= reads it's own immediate output before any resistance is added to the system, thus causing voltage loss down the line.
3-wire system= uses a remote sensing wire to adjust it's built in voltage regulator in order to maintain 14V throughout the entire electrical system.
So- why did Ferrari put a 1-wire system?
I don't know, why did they put those early style fuse boxes in either.
The way I see it, you can add a bunch of relays to make your system work as it should ensuring that the relays are fed with the 12-14V produced as it enters the fuse box or change the alternator for one that ensures the entire system maintains a proper working voltage. The problem now is none of the current 3-wire systems fit---that is until now.
I'm currently adapting my brackets to accept a 120 Amp Delco/Remy 3-wire alternator instead of my 65 Amp Bosch to my 82 Mondial- If it works I'll post on here the How-to (oh yeah, I guess I should mention it only cost me $85) The alternator is very, very, very close to the exsisting Bosch 0 120 469 537 unit I now have. If it doesn't work I just spent 30 minutes writing this for nothing... wish me luck.
If you go for the Delco alternator and tune it up with HD rectifiers and a 3 wire (sense) regulator, you can let it monitor battery voltage and you will have a fully charged battery in the future.
Went trough this with my T.
The regulator is available in many different versions.
If you take (or already have) one with a "sense" input and route a thin wire to the battery, it will take the + terminal as a reverence. Thatís all.
Maybe you have to get another connector for the alternator and connect it to the cars loom.
In the thread are some links to suppliers with good online catalogues. There you will find something that fits your requirements.
At these pages you find more basic information. They have some special hard to get parts too, even if they are a little expensive. Anyway, the info is great!
Many regulators have the sense input, but donít use it. You only have to connect it, (maybe, better to fit a fuse near the battery)... yes, that easy!
IMO going for larger alternators is not the best way on a Ferrari!
Large, heavy parts rotating at high speed can create other problems, like broken supports or even worse thingsÖ
The 105 ampere of a CS130 should be more than enough, even a 65A unit should do the trick, but only if they reach the battery with the proper voltage.
Larger batteries give a much higher load if they are part empty, as often on our cars. The high charging current plus high rpm plus high engine bay temperatures kill the (often lousy assembled)stock units, thatís my theory.
I use a good 40AH battery on my T and donít find any problems with it. Why carry a truck battery if you donít need it?
A lot of what you wrote is very good but your example is incorrect: "A good example is a row of lights...if you hooked up lights in DC series circuit, you would notice that when you look down the string of lights, the first one is much, much brighter than the last one."
If all the bulbs in the row are the same wattage they will all be equal in brightness. Remember the big old Christmas tree lights? They were wired in series (if one burned out the whole string would go dark) and each lit up with the same brightness.
this is in fact the problem with older cars. The resistance gets higher.
The Mondial has the battery far away from the alternator and the voltage at the point that the regulator sees is higher than the voltage at the battery + terminal.
So the battery is permanently undercharged, what causes problems.
Newer regulators donít have the sense input because this is no usual problem!
The temperature compensation of the regulator makes things even worse, as it sees the high engine bay temperature and reduces the voltage even more when hot, while the battery in fact stays pretty cold... some regulators even sense the battery temperature in special applications to compensate for this.
Ferrari did not put one additional wire (only a thin one, as it does not transport current and so has no relevant voltage drop) from the alternator to the battery.
Copper is expensive and Italy is a poor country :-)
Ferrari has not taken too much care about things that might happen when the cars get 15 years old!
So today the owner has to sort these problems, even if some see this questionable.
But it is a reality in 2007: In some points we can make these cars better than the Ferrari engineers in 1990 designed them.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.