How far can I drive with a bad alternator?

Older cars can go much longer on a battery... maybe an hour or so. However, the newer the car, the less the range. In a '95, I'd think 25 miles would be above my "comfort" level... though I think you'd have a reasonable chance of making it. I use AAA for things like this... it pays for itself nearly every year (I play with a lot of old cars...)

Bill

 

Ditto on the AAA membership. I went one year without using mine at all, and the following, needed it 3 times. It's definitely worth the price of admission for peace of mind.

 

Hi,

I would agree to be safe and tow. It's hard to be sure the battery is in great shape, even on a fresh charge.


Larry

 

on a "fully charged battery" you can make it

i did, even further than that actually

run the car without the AC on, no radio, no lights, etc...drive 60mph ...and you'll make it

 

Jeff,

It will make that distance, and much further, no problem, but as Joe says keep everything that uses current switched off.

Donie

 

I'd risk it...but bring along your AAA card.

 

Drive through good neighborhoods.

 

Agreed. If the battery is in good condition you will most likely make it but plan on changing it after the alt is fixed.

 

The real problem is not how far you can go on your battery, but why you've blown up 5 alternators in 5 years.

One thing that will kill them is heat.

Heat on 348's and 355 alternators tends to come from one or more of 3 areas:
1. Belt too tight
2. Missing exhaust heat shield to protect alternator
3. Battery with a failed cell that causes alternator to work at max power for too long attempting to keep the battery charged.

The other deal-killer for 348/355 alternators is a jump start.

...And alternator shops that use cheap Chinese replacement parts for the repair will also cost you.

You say above that you use a battery tender. Why? Is it because your battery isn't holding a charge on its own? If so, replace your battery with a decent new one (e.g. Optima/Nascar).

Your mechanic can place an ampmeter on your battery while it is in your car to view the load when your car is off (could indicate a short circuit or faulty component somewhere in the car) as well as when running (which can help identify if your alternator is being asked by your car to work too hard for too long).

A $20 Kricket tension gauge will also tell you if your alternator belt is too tight. I'm not sure about the F355, but on my 348 you just remove the one engine under-body piece of armor (6 bolts), stick your hand up on top of the belt with Kricket gauge attached (it has a ring for a finger to hold it), and press the little black button. You don't want more than 135 ft/lbs on that belt (you don't want less than 90, either).

Find your core problem; fix it! You'll be happier for doing so.

 

Sure. Have your mechanic place an ampmeter on your battery while the battery is in your car. View the current drain while your car has its engine off, and again while on.

Have your mechanic use a heat probe on your alternator while your car is idling.

 

Just curious....does the dealer have a go at trying to fix your alternator problem? Or do they just sell you/fit a new $1000 alternator and send you on your way? Besides this one,now under warranty. Will they have the car for a few days to have a look at the charging circuit ect... or will they fit another new one and send you on the way again....till next time. Has the dealer ever mentioned what failed in the last 4 alternators of yours?? Knowing that,would be the "key" in putting you and us....even them on the right path to fix your problem,to end this '1 alternator per year fiasco'

 

Each time the alternator went bad, did the dealer/replacement shop indicate what failed on the alternator? Did the rectifier pack burn out?? Assuming all the mechanicals are in order, I would go along with the thought of putting an ammeter on the output of your alternator while the car is running and measure the max current drawn from the alternator with all your accessories turned on. Does the draw exceed the rating of the alternator oputput? Also take a measurement with the car ignition turned off. Only other thought is a bad ground or other high resistance connection in the alternator circuit. Is your battery voltage around 14.5 volts when the car is at idle? Significantly higher or lower could indicate a problem (2 volts or so). A failure once a year sounds like something other than your replacement alternators. Good luck.

 

Besides the #1 ampmeter and the #2 heat probe (for the alternator/engine bay), at the very least you should #3 ask to take physical possession of your next/current failed alternator.

With the bad alternator in a box, you can go to a friendly magneto shop where they will tell you what failed (and not care that it came from a Ferrari).

Then I'd take out your #4 old battery and have it load tested at AutoZone or wherever. It could easily have a failed internal cell.

The above 4 things would give you information that you don't currently (pun intended) know...letting others on Fchat have a pretty decent shot at narrowing down the root cause.

Otherwise, you're going to continue this 1 alternator per 6 months bit...or faster (if an internally failed battery is the cause, leaving that battery in your car will fail new alternators progressively faster). 6 months for your last one, then 4 months on the next one, 2 months on the one after that, etc...

 

Read post 13 again. Have they ever told you what happened to the other 4 alternators. WHY they failed?? Or do they sell you a new one,then send you on your way for another 6month to a year?? Maybe its time you went to another dealer i think......

 

just a thought it wasnt replaced the first time and the wrong alternator has been fitted.alternators get hot we know that.maybe yours lacks output e.g 1x fitted 70amp output /original alternator 90.maybe the cooling fan is incorrect(by the pulley).bad earths and connections love alternators.any connectors on it make sure there are no breaks.follow the wires back.is this the only problem you have had .nothing else related.shorts /opencircuits. goodluck Tony

 

Look at the engine bay jump posts. Some of the alt problems can be traced to loose or dirty connections at the com bar. The connections heat up from high resistance, the plastic melts and the connection gets looser yet.
Another problem I have seen is the use of cheap Delco replacement units. Rather embarsing but I have never verified what was told to us in a Ferrari school. FNA officials told us that the internals were wound tighter and secured better than the units made for NA cars which does have some logic behind it. I have seen and verified it on the 348 Delco units prior to the N Denzo fix but have had no problem with the 355 units after the ground straps were installed. A Chevy was designed to cruise at 1800 RPM but that is just the warm up RPM of the 355.
How much have you been paying for the alts? I know the price of a Ferrari unit would give the boldest cardiac arrest!
With a good, fully charged battery, on the highway with no fans running, 25 miles is no problem with stock electrics. Drove a Vega from Jackson Hole to Mpls with 2 battery charges in route using parking lights and radio back when I was young and dumb enough to do marathon drives.

Dave

 

The main problem with driving with a bad alternator is if the problem is with the bearing at the pulley. If it seizes you get a hell of a smoky mess and risk breaking the belt. I've done this, not too big a deal, but scary and has the possibility of throwing little bits of belt and what not around the engine.

You can also drive the car with a spare battery in the passenger seat and jumber cables going back to the engine. Kind of hoaky but works.

I put a groundstrap on mine after it seized up and haven't had any problems since.

 

When the alternator belt went on the 550, the dash started lighting up like a Xmas tree and the car was gone within 6 miles (in traffic). The last thing to go was the power steering. The guy came with a battery charger, we hooked it up, layed it on top of the motor and made it to his garage (1 more mile).

 

I did it several times in College on my 5.0 Mustang. It went through a phase where it wanted to eat accessory belts and I had it towed the first time. I think two other times I gave it a shot and it worked out good. All the times I lost the belt, it was about 30 miles from home. The only thing was that running with no belt, I had no power steering, or water pump so I would fire it up and get going like 90 miles an hour and then slap it into neutral and shut the engine off and coast for a few miles. This few miles of high speed coasting would allow the engine to cool off enough to fire it back up once the speed got down to 30 mph or so and accelerate back up to 90 or so and then shut down again. It worked like a charm. It took a little while, but it saved a poor college kid a $100 tow bill. The only thing is you have to watch the temp guage like a hawk and keep it from getting too hot. On a Ferrari I would be wary of the low voltage hurting the electronics. Maybe it wouldn't, but it could really hit your pocketbook hard if it took out your ECU's or another part of the electrical system.

 

The belt is on isnt it. If it is and battery terminals look good,connections good /fuse good blah blah.If you cant remove the alternator yourself.buy a cheap or dear volt meter.Connect.----------- what have you got 11.9or13.6 roughly.One is charging the other isnt(right).you are 1/2 way there .Tools /yes .Disconnect battery or switch/do both yes(radio code).Loosen belt/wires/remove bolts.babe look what i did.ID alternator(is it a factory fit for this car or will the stator ---- itself at 6500 plus.Or is it more a case of charge,drive, survive(new i should have trailered it).They still look cool on trailers.whatever you dud goodluck Tony

 

several years ago, the alternator on my 86 tr went bad and i only made it about 2 miles. thank god for aaa flatbed.

 

Don't want to second guess your professional mechanic, but my suggestion would be to attempt to isolate the route cause of the problem. The first thing to do would be take the bad alternator to an independent source for testing (Auto Zone) and make sure it was defective. If it is bad, then it would be a good idea to dissect it to see what failed.

I had a Datsun Pick-up that ate alternators and after several R&Rs I determined that it was due to high speed driving and a flimsy Alternator bracket--the later trucks had a cast iron bracket (mine was steel). It seemed the alternator was located quite a distance from the block and it apparently would get shaken to death. The last time it failed something came loose and shorted the harness out and the harness caught on fire. I immediately changed the bracket to the later design

On your car, if possible it may be good to run it at a high RPM while watching to make sure that the Alt is not vibrating a lot? Perhaps there could be some kind of a stabilizer strap missing? (American cars had some extra straps that in some cases would get left-off) It would be good to verify all the attachment hardware was tight too.

As far as driving to the shop—you could take and extra battery. Also, you could rive halfway there then charge the battery with another vehicle or a charger.

Best,

Mark