help! alternator

My first thought would be a poorly rebuilt alternator, although you should also test the battery to make sure it's not killing alternators. Easy enough to check the alternator by reading the voltage across the battery with the engine running. The manual probably gives specific voltages but a good battery and alternator probably ought to be reading over 13 volts. If in doubt turn on the headlights and see if the voltage drops-- a good alternator should produce over 13 volts even with the lights on.

Considering you've experienced two charging system issues in rapid succession I'd also check the battery though, even if you confirm that the alternator is faulty. While a bad rebuild seems like the most likely scenario in this case, bad alternators can kill batteries and bad batteries can kill alternators, so worth checking for open or shorted cells, as well as overall capacity, particularly if it's an older battery.

 

check or replace the battery.

 

thats right you must have 94-95? On my 90 348 it easy to check battery since its right there in the back. To test you would use a volt meter on the terminals once when car is off to see what its static charge is and also while the car is running to see that the alt is in fact sending charge to the battery. Sometimes batteries just go bad after sitting and wont hold a full charge even though they seem fine on the volt meter. All in all take it out and get it load tested at a reputable place (not one that just wants to sell you a new one). also take you old alternator to a reputable place as well and have them load test that too. Perhaps when the shop put the car back together they forgot a ground strap or something? But overall I'd take the battery out and test it first, then test alt

 

The OP owns a 355, so his battery is up front.

Yes, it would be a good idea to check the battery with a proper battery tester. I'm guessing the OP doesn't have a Midtronics tester sitting on the shelf like I do, so that complicates matters since it requires removing the battery and taking it someplace. FWIW, my local Pep Boys has a nice Midtronics battery tester so that might be a good option if you have one close by.

But I'd still check battery voltage with the engine running first. If it's under 13 volts it's a pretty safe bet (although not a complete certainty) that the alt is bad. That's my guess based on the fact that the alternator came from eBay.

If the alt is indeed bad my suggestion would be to check the alternator rebuilder thread in the main tech section and send it to the one that gives you the warmest fuzzies. That's what I'd do if my 348 alternator failed, even though I repair cars for $. Where I live the local rebuilder is not someone I'd trust for an alt that's difficult to access, so is just as soon work with a more professional outfit even though it'd mean shipping it off.

While the alternator was on its trek across the country I'd check out the battery just to make sure it's okay. I've seen a whole bunch of instances of one killing the other and both winding up bad, so I'd rather know for certain the battery was okay when I reinstalled the blingy rebuilt alt.

Best of luck and please update us with the final solution.

 

Check battery cables and wiring first. Loose connection at battery may have caused both. Unlikely new alternator is bad. Rebuilding one isn't rocket science.

 

Make sure the ground cable from the alternator to the chassis is no missing

 

Clean all gunk you find too. That white oxidation can kill your juice.

 

A quick search of the 348 DIY stick yielded this -> http://www.ferrarichat.com/forum/technical-q/142329-348-alternator-removal-rebuild.html Be sure to read the ENTIRE thread before you start your rebuild. Some alternators have different housing sizes an thus some replacement parts my not fit.

The search button is your friend.