355 alternators suck!

I have a friend that use to have 1969 Dino 246 with alternator problems. Had it rebuilt twice. The problem turned out to be a missing heat shield that killed the diodes. (the exhaust manifold creates a lot of heat)

I am not an electrician but ... has any one measured the "AC voltage" at the battery @ about 2K RPM? If it is greater than .4 to .5 AC then your diodes are starting to go…… Check with the alternator rebuild shops … they should have a spec on this. It may vary from one alternator to another.

This AC voltage can/may also play havoc with some models on board computer systems and electronic fuel injectors…

 

I don't know about the 355, but the 348 Workshop Manual warns that our alternators will consistently overheat and fail if the alternator belt is too tight (causes overheating of the unit).

Just a thought if you've had more than one failure. Someone who means well may be overtightening your alternator belt, perhaps.

 

Conversely, if the belt is loose, slippage will cause heat buildup on the pulley, which migrates into the front bearing, frying the grease .... I just dismantled my F355 alternator to fix a dead voltage regulator, and this had happened.

Al

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This company is advising me on how to fit this brand new style of regulator with welded diodes into our 348/355 alternators. So far they have been very helpful.
The only difference is the B+ stud is 6mm instead of 8mm. Apparently I can swap B+ studs. Other than that, a direct bolt-in.
This is a MUCH more reliable regulator.

http://www.transpo.de/cgi-win/product.exe?INR734P

JayM

 

And wouldn't you know it comes off of a Dodge minivan. Comedy, pure comedy.

By the way, do those guys offer a complete rebuild kit?

 

Hi All

This is a very old thread but I'll add something anyway.

I have a 1992 348TB (European model) which I bought second-hand (or as Ferrari prefers to say - "pre-owned") in 1996. It was my first Ferrari and I thought that it was great (which I still do - even if it is presently sitting in the garage in an undrivable condition due to some typical electric problems, which is however another story and one of my winter projects ;-).

So me and my wife took a ride from central Europe to the United Kingdom for a short stay. The trip over was great but, after arriving at a friends house, the doors wouldn't open (I had locked them while driving for some reason) and only after waiting a couple of minutes the door lock reacted to pressing the unlocking button. Of course the car wouldn't start again since the battery was completely flat (strangely there was no warning light on at any time to indicate that the battery was not being charged while driving...).

After recharging the battery it was possible to start and drive over to a battery/alternator shop where the battery was checked - no problem with it (discharge test was fine). So I arranged for a small garage to remove the alternator and the shop did a recondition of it, including replacing the blown rectifier bridge circuit; the original alternator was from MAGNETI MARELLI. They charged £100.

All was great until we travelled back. On the way down to the south coast of England, with the sea in view (destination ferry back to continental Europe) the red battery light came on when we slowed down approaching a roundabout. Assuming that the rectifier bridge must have blown again I bought a new battery (it was a Sunday, but fortinately a small car parts shop was open - since the ferry would be leaving shortly there was no time to do much else). The spare battery had to be carried somewhere in the passenger's foot-well but my wife was (at that time, since we hadn't been married for so long) quite understanding (if it happened today I am quite sure it would have been a different story...).

We did make it a couple of hundred miles into France before the first battery died. I had stopped at a store and picked up a cheap multi-meter and wired it up to the 12V in the middle-console to be able to monitor the discharge. We also drove on the motorway (normally I would have preferred to use the smaller roads since they tend to be more fun) at a constant 50mph in the hope that it would allow the greatest distance.

The first battery failed just as we had to stop at a toll gate to pay for use of the motorway stretch. After paying I had to get out of the car and push it past the barrier, where I could then do the first battery change.

The exercise was repeated as two more batteries were bought on the way. My wife now had to share the passenger well with three batteries, which we also had charged up in a garage at some point to ensure that we always had reserve energy when needed.

We arrived at a hotel where we planned to stop for the night before the final part of the trip, where they told us that we should take it to the local garage and suggested that they led us the way. Not wanting to appear ungrateful I accepted and also arranged the shipment of a new bridge rectifier.

It took three days before the bridge rectifier actually arrived so we stayed at the hotel for this time. When it arrived I went into the garage where they had just opened up the alternator to build it in, where it became evident that it wasn't the rectifier but instead the alternator winding had broken off from its contact point. The garage had a huge soldering iron (about 15mm wide) and couldn't get the solder joint to fix, which meant that I jumped into a car with one of the mechanics and drove around to various companies with the alternator under my arm until we found a place where they had a 'normal' soldering iron which we could borrow.

That fixed, we were off again and made it home and all was fine for several weeks until the red battery warning light came on again (at least we had a bridge rectifier in case it had really blown again this time). So I gave the alternator and bridge rectifier to a local company (don't know why I didn't do it myself though) who decided that the alternator needed a complete recondition and charged about $400 for the job.

A short time later (the alternator was still holding out) I happended to talk to someone at Ferrari who said that there had been a call-back of the 348s for an alternator replacement (Nippon-Demo) since the original ones were too weak. If I had contacted Ferrari the replacement would have been free of charge - even though I hadn't bought the car new; however it was now a bit late - the replacement alternator was still offered but the cost to build it in (about 3.5 hours work due to change of cable looms etc.) would have to be paid.

So I paid for the replacement and since then have never had any more problems*.

What surprised me the most was the fact that the 348 actually ran better with the new alternator. I didn't realise before how important the battery level is, but I am convinced that everything was that bit more lively with the new alternator presumably generating a better charge and possibly slightly higher voltage for the general operation.

*In the following two years both catalytic converters broke up (the ceramic parts broke and crumbled) but I don't know that there is any relationship between the episode with the alternator (I never had any back-fires etc.) and expect that the previous owner didn't drive much and the damage came from condensation in the exhaust, for example.

Cheers

Mark


[1992 348TB and 1988 Mondial 3.2 Cabriolet]