Looking for Diodes for 365GT 2+2 alternator

[perry911113]

I trying to help friend locate a source to obtain diodes for his Marinelli alternator out of his 1969 365GT 2+2.

Any direction would be of great help.

Peter Perry

[TOMKIZER]

Hi Perry,
I've no direct experience, but the book, Ferrari Tuning Tips and Maintenance Techniques by Apen and Roush recommends replacing bad Marelli alternator diods with a diode kit from Motorola Automotive Products. I don't know where to find the kits. They discuss it as if they are readily available, but I don't know that.

Apen and Roush say, "Replace diodes with red markings with Motorola part no. 2-1: replace those with black markings with Motorola part no. 2-2. These are 25 ampere 100V diodes that must be pressed in and out. Be certain you have the proper equipment -- a small press -- to handle the job. Use caution when pressing the diode in. Do not apply pressure to the lead or glass seal area. Solder the leads carefully and quickly to the diode lead. Trim lead to length if necessary. Check the diodes to be sure the test light functions properly."

The above book is worth having for anyone owning a vintage V12 Ferrari. It describes lots of interchangeable and equivalent repair parts throughout. Available often on EBay.

Good Luck!

Tom Kizer

[Jimmyr]

Perry, Motorola has been out of the automotive alternator business and the semiconductor (diodes) business for some time now. The style of diodes has also changed from the pressfit type as your Marelli is, to soldered assemblies, and therefore the old pressfit diodes have not been in production by any noted source for some time now. Many of the remaining alternator rebuilders have either a stockpile of the old pressfits or they have some unique offshore secret source for them. In any event I would suggest that you contact one of the current rebuilders, such as Bosch people or Prestolite and see if they will either sell you some diodes or have them rebuild and test it for you. Note, that the Marelli alternators and starters were made under Bosch license back then, and the rebuilders usually have no problem rebuilding Marelli electeics. Jim

[TOMKIZER]

Jim,

That's what I love about TomYang.net. There's always someone who can provide an update to the technologies and techniques of the past. The third edition of the Apen/Roush book was in 1975 and the 22nd printing was in 1989. I don't know if that was the last.

I think I'm going to print your post and insert it into my book as an update for when I eventually need it. Thanks for the info.

Perry, I'm sorry for providing obsolete information.

Tom Kizer

[Rudy van Daalen Wetters]

Marinelli- Detroit Lions disaster!

Rudy van Daalen Wetters
1963 GTE s/n 4001
1966 330 GT s/n 8705

[Dan Sands]

I was able to get them from a local alternator shop and they were cheap. Just bring a sample with you. I believe your alternators should be 55 amp. They also had brushes that were close and I sanded them to size. It should be an easy and inexpensive rebuild.
Dan