[DeTomaso] Alternator Options

[Kirby Schrader]

I would agree with your assessment, Doug. The little #8 and #10 wires are too small.

I use a 130 amp alternator on my Pantera and a 200 amp alternator on my GT40.
Both have been rewired to use a #4 cable from the alternator to the battery and to the fuse box.
Agreed. Even the #4 does not theoretically meet such loads for continuous duty, but those ratings 
are very conservative and the lengths used are' short'.

I don't use an ammeter anymore on either car, but I honestly do miss what I thought it used to tell me.
I've just had to learn to observe the voltmeter and 'think differently'.

One thing I did learn though... if you have a huge alternator, then the belt you are/were using is probably too small.
The next modification to make.

At least, as has already been pointed out, you most likely will not need the full alternator output continuously, if ever.
I use such large ones because the output at idle, where you usually have problems 'keeping up', is so much higher.
For example, the 200 amp unit puts out over 100 amps at an idle speed of 1000rpm according to the manufacturer.

FWIW,
Kirby


On 28 Nov 2010, at 02:59 AM, doug351c wrote:

> Mike,
> 
> My intention is to caution owners to not add more alternator ampacity than
> is necessary.  Your burned wire harness was likely due to the ammeter.  The
> Pantera ammeter has been known to have loose internal terminals and is a
> known fire hazard if it has not been inspected for such.  I found that after
> tightening my ammeter's terminals, it still needed a 16AWG jumper to make it
> read correctly (as verified by an NIST traceable calibrated Hall effect DC
> reading Amp meter).  Consider also that the 4AWG wire leading to and from
> the ammeter has a continuous rating of only 60A not 100A.  If the voltage
> regulator fails, it can tell a 100A alternator to provide maximum output
> which can lead to a fire.  I do not recommend a 100A alternator in any
> Pantera that has not had it's ammeter and associated cabling upgraded to
> handle the increased output.  I would welcome SO Bills comments here.
> 
> Doug
>  -----Original Message-----
>  From: MikeLDrew at aol.com [mailto:MikeLDrew at aol.com]
>  Sent: Saturday, November 27, 2010 10:58 PM
>  To: doug351c at gmail.com; jskeane6 at gmail.com
>  Cc: detomaso at realbig.com
>  Subject: Re: [DeTomaso] Alternator Options
> 
> 
> 
>  In a message dated 11/27/10 22 30 3, doug351c at gmail.com writes:
> 
> 
> 
>    I know of other Pantera owners who've installed
>    100A alternators and burned up their wiring harnesses.
> 
> 
>>>> I wouldn't necessarily assume that it's causative however.  Can you
> draw a straight line between the alternator install and the wiring harness
> issue?  I doubt it--there were probably other factors involved.  My Pantera
> came to me with a burned wiring harness too, and a stock alternator.
> 
>  And that alternator didn't work worth a damn keeping the old battery
> going; I could sit at a red light at night, with the fans, headlights and
> A/C running, and if I didn't keep the rpm up, eventually it would kill the
> battery and the car would quit.  I'd then have to push it to the side of the
> road, turn everything off and wait for awhile for the battery to recover and
> the car to cool off so the fans would shut off.  Not fun!
> 
> 
> 
>> Excess alternator
>    capacity is not necessarily a good thing.
> 
> 
>>>> Very true--but more Panteras than not are running 100A alternators now,
> so I wouldn't consider that 'excess'.
> 
> 
>> As long as your ammeter shows a positive reading, your alternator is
> keeping
>    up with the load and this is an average thing so at idle it's OK to read
> a
>    negative as long as it reads positive with a few additional revs.
> 
> 
>>>> That depends on how long you drain the battery like that.  My ammeter
> reads slightly positive even at idle with the fans running.
> 
>  Just because an alternator can produce 100A doesn't mean that it always
> does so.  (Somebody correct me if I'm wrong).  Depending on the demands of
> the electrical system, it can produce UP TO 100A.  If the demand isn't
> there, the alternator doesn't put out any more juice than a lower-amp unit.
> So it's not going to automatically pump all sorts of power into your car.
> But if you have heavy loads on the electrical system, it should have enough
> hump to keep you in the positive and keep from running your battery down.
> 
>  SOBill or somebody with some serious electrical smarts, weigh in here and
> let me know if I'm all wet on this?
> 
>  Mike
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