I think so too. Just using sixth gear as much as possible at Daytona has helped. I never reach those speeds at Watkins Glen and Sebring and certainly not at Lime Rock Park. I'm still on the same replacement alternator installed right after that Daytona event more than four years ago. But when they fail, they do so rather quickly. That's why my car travels with a spare alternator. Over that two-day event at Daytona in 2015, three other F355 Challenge cars had their alternators fail. One driver had his alternator rebuilt locally overnight and reinstalled the following morning before the first session. We were all using 5th gear as our top gear and spending lots of time circling the track at over 8,000 RPM.
Could be. Whenever our alternators are replaced, no attention is given the stock pulleys on them. We should really modify our new alternators with slightly larger pulleys. I'm not sure if anyone has ever researched how much larger they can be and still allow charging the battery at idle.
A friend of mine works at UW Madison Science Department. Good problem for their engineers to figure out.
Grounding is important too. I clean the alternator to engine block and engine block to frame contacts regularly. I added an extra ground strap from the engine block to the frame where the A/C compressor was once mounted...
I see Denso has different pulleys that are slightly larger. Don't know if belt will fit a bigger pulley and not much room for a bigger pulley. Going to experiment with my spare alt once I get that one rebuilt.
I have a really odd problem with my 355 5.2 alternator, the dash red warning light for the battery is on all the time but the alternator is charging. I have checked this many times after a run out, and everything is fine. I have refurbished my alternator with all the standard failing parts and this still hasn't cured the battery light coming on. I have also added an additional earth point as I have seen threads where this can be a problem. Has anyone got any idea what I can do to resolve this battery warning light issue?
It could be the connector on the small red wire which runs between your alternator and the battery shown in this diagram (bottom left hand): Injection/Ignition System 5.2 It's labelled "R - 1.5". I'm not sure where the connector is (perhaps near the battery). Since the battery is so hard to get to, you could check the voltage going to plug 41019 (It's the 12 pin plug near the left hand rear shock absorber (under the side cover plate). Shown in this post: https://www.ferrarichat.com/forum/posts/146655635/ Check for normal battery volts on pin 9 (engine off). Don't disconnect that plug with the engine running. See my diagram for the pin/socket numbering on that plug. I don't know if you've taken the side cover off before, but you'll need a 3.5mm allen key. Do you have a standard bulb in the warning light?
Yes, check the "sense" wire it is probably broken. My friend has this issue, it is not uncommon. The (red) wire will typically break at the positive battery connection. The wire is actually molded right into the lead clamp. Solution was to splice a few inches of additional wire to what was left, and add a ring connector and attach that way to the clamp. Fixed! He was messing with this for months trying to resolve the "batt" light constantly on. It comes up regularly here.
Replaced my alternator , tensioner bearing and still would not charge. Turned out to be a broken wire on the 3 wire plug. Wire insulation was hiding the broken wire. Should have checked this first I guess.
Hard to tell, colors have faded with heat over the years. Maybe brown wire although they all look brown! Ordered new plug with pigtail wires that I will solder to old wires, shrinktube and fire sleeve the wires.
Interesting... Exactly what has happened to me last W/E. I have a mini digital voltage reader that sits between the cigarette blades in the ashtray. This was telling me the alt was charging(as the engine rev'd up), but at a lower voltage. Max was sometimes at 13.1V, but most of the time was between 11>12V! I actually have a Denso rectifier on order to replace. The little digital reader is completely removal-able should the next owner dislike. Hey it's worked for me!
It fits right in, requires almost no power to work(won't drain battery) and can be hidden by closing the ashtray cover. May not be completely accurate but once viewed for a day, will answer any changes to charging... Image Unavailable, Please Login
Well i checked the wiring and you were correct faulty battery connection, spliced in a new wire and all works now, many thanks
Well i checked the wiring and you were correct faulty battery connection, spliced in a new wire and all works now, many thanks
Looks like tons of room for a larger alternator pulley. Where are you running into a clearance problem?
I take it back. There might be room for a bigger pulley. Denso makes a lot of different sizes. Would have to make sure it is not so big it does not charge at idle. Would need a bigger belt. Next project. I think it would stop the alternator failures.
Bob, do you have a good solid ground cable or very thick wire from the back of the alternator stud, to a point on the chassis? It wasn't until 1998 or there about that Ferrari put one on the F355, and was a free update by the dealer when the cars were in for service. (not a recall) If you look in the parts look up, you will see it for the 5.2 cars, but not the 2.7 See part #63 https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/355-group/f355-m5-2-1996/current-generator-starting-motor-battery.html Charging issues was a problem when new, until this update came out and early cars retrofitted.
I have the factory ground. Ground is not the problem. I think high rpm kills the alternator because it spins do fast at high rpm. A bigger pulley would slow the alternator down. Common solution
If you place a larger pulley, you'll get LESS amps at idle. AFAIK, most stereo guys do the exact opposite, smaller pulley/more amps at idle. Idling a Ferrari is exactly what kills the battery, especially when all the fans are on, as the alternator beats itself up trying to charge up the battery. As I understand it, that's why many plug in a trickle charger, to keep the battery at full potential. If one leaves a car sitting for say 3 weeks, then drives it in city traffic on a hot day, the alternator will work too hard, and die an earlier death. my .02
Hi Sandy, Yes, any change in the pulley ratio should be specific for the car model and its primary use. The side discussion between Bob and me related to how our cars are used. Mine is used only for HPDE track events. Other than warming the engine up for ten minutes prior to the first run of the day, my car spends very little time idling. My car has no air conditioning or sound system and I manually override and turn on both cooling fans only on very hot days when I get out onto the track. On big superspeedways like Pocono and the Daytona 24 Hours Course, my engine spends a lot of time at high RPMs. I've learned to keep the RPMs down a bit by grabbing 6th gear whenever I can. It means two or three extra downshifts per lap but that's okay, It's just HPDE and not racing. I think the stock alternator pulley can be swapped out for a slightly larger one but such a change would have to be carefully thought out by a racing alternator specialist taking my car's specific electrical needs into consideration. Right now, my car is handled by Jim McGee at Pocono Sportscar. He knows my car best as he helped develop the 348 and F355 Challenge cars when he worked for FNA. He's not inclined to change the alternator pulley ratio right now and wants me to continue driving the the way I do at Daytona and continue carrying a spare alternator with the car. Bob's specific use of his car might be different and I'll let him comment himself. Barry
