Hello All, I've got a curious electrical issue on a 1971 246GT. It was standing for a while, but is now running again. Electrically, I've replaced the battery, the starter motor, the HT leads and I'v rebuiilt the distributor. The only other thing whichI did which might affect the electrics was some MIG welding to the handbrake mount on the chassis. The battery was disconnected when I did this. When I start the car from cold, the dash mounted ammeter registers a massive positve reading at anything more than 1000rpm - like 40amps positve. The needle on the ammeter moves very abruptly with revs, almost like the regulator is having no effect at all. Within a few seconds it seems like the regulator kicks in and the needle no longer moves as abruptly and shows a slight positive charge when the car is revved - as it should. The regulator fuse has blown several times, but it does not happen every time I start the car. I've replaced the regulator, but this has not cured the problem, so i suspect it is the alternator which is on the way out. Before I go through the trouble of replacing the alternator I thought that I would ask and see if anyone had come across this problem and there might be an easier fix. I'd appreciate any help, because I don't really relish the though of replacing the alternator. Thanks in advance, Andrew
I share your anxiety in replacing the alternator Andrew , a job to avoid if poss. Did the wiring overheat on the firewall fuse box? Check for a short circuit in the wiring / cables to ground, those cables can get pretty hot at that charging rate, also check the terminals on the ammeter [ plus fuse carrier] are clean and no high resistance as this can lead to the problem you mention. Tony
I haven't had your problem, just an overall diming of lights and reduction of power. As Tony pointed out, it turned out to be the terminals on the Ammeter. I retightened them with nylock nuts so it wouldn’t happen again…
Thanks Tony. The firewall fuse box does show some signs of overheating, so that might be it. Much obliged for the helpl
I’ve replaced about everything in the system. My ammeter shows a lot of fluctuations at start up and then settles down within seconds as described. Not sure mine is doing the same thing as yours, but it may be normal. Post a video.
Same happens with my 330 GTC. Once the engine starts and runs at fast idle the ammeter bounces and pegs at the max. After a short time it settles down to be slightly positive. Once on the road the more you load [a/c, cooling fans, lights, etc] the meter will read negative at idle. Rev and it will go positive and once again settle down slightly positive while underway. Unless I am missing something this sounds very normal for vintage Ferraris....and I have had a few including a Dino.
Perhaps take the front, right wheel off, remove the passenger's side front wheel well splash panel and inspect the wiring bundle as it makes turns into the rocker panel run. Dino 05082 had an intermittent short on the wiring loom where it passed on the Passenger's side front wheel well into the rocker panel run. That edge wore through barely enough to cause rare shorting, finally ended up burning fuses out. I was getting a lot of violent Ammeter fluctuations before I found this and it was not easy to track down - absolutely frustrating to be driving along to see that all of a sudden the Ammeter randomly swings full negative then returns to normal. PS - there is a 60 Amp replacement on the market which will fit in the OEM Dino instrument canister, simply swap the guts, although new needle range would be 60 not 40 amps. MoMa did the conversion for Dino 05082 after the above incident
