Testarossa Battery Question

Gabriel - in cars with generators rather than alternators, the generator created voltage at its terminals. Alternators are really current generators. With respect to a 1969 model, I suspect that it had an alternator. However, the spark and timing were mechanically created, by that I mean, current flowing through the coil interrupted by the points induced high voltage in the coil secondary. In theory, and in practice, a car could run without the battery (I guess - as I have never tried it). In modern cars, so dependent on stable voltage, it becomes problematic.

Current generated by the alternator will seek ground. If it can get to ground through the points, and then through the coil, it will induce secondary voltage and consequently spark. However, I suspect that your radio would not work with the battery disconnected.

As a general rule, lead acid batteries are charged by current flowing through them, and it is their internal resistance that produces voltage (V = I x R).

Have others found that their car runs with the battery disconnected?

Jim S.

 

Yes, it was an alternator. Alternators had replaced generators for many years before then. Offhand, I can't think of any car in the 60s that still used a generator. Heck, I don't remember any 50s cars either. I was too young to know any of that then, but I did have a few friends in the late 60s that loved to mod the 57 chevy, and I'm pretty sure they used alternators, although I suppose they could have been converted.

Batteries then, like tires, were nowhere near as good as they are now.
Dead batteries were pretty common and everyone carried jumpers.
I remember many times starting a friend's car by swapping out the battery to start it, and then removing it so they could get home or wherever, and all the accessories and lights worked just fine, even at night.
You had to wrap the positive cable clamp with a rag or such so that it didn't short to ground and stall the car (no plastic battery boxes then) but other than that, it was pretty straightforward.

Now, if the alternator failed - this happened to me once when a serviceman (anybody remember them?) spilled oil on it when he was adding oil.
It was night and as the battery slowly went dead ,the lights dimmed to zero and then the car died. A real pain before cell phones.

 

DO NOT EVER DO THIS!

It IS VERY fast but it may not be free. By disconnecting the battery from the system you will be allowing spikes to possible damage your electrical components and we all know how expensive they are! It IS your car and you can do as you wish but I HIGHLY advise against it!

Stuart

 

The resting battery voltage is a bit low but it depends if it's just been charged lately or not. I would use a load tester on the battery just to check it's condition but your real fault lies elsewhere.

Alternators produce 3 phase AC power at their stators which is rectified (converted to DC) by a 3 phase full wave diode bridge assembly. The stators are usually wired in a "Y" wound configuration for cost reasons and as far as I know only aircraft alternators use the superior "delta" wound configuration. What this means is when you have a stator wire fail or it's associated diode, you will loose 2/3 of your alternator output!

Your "idiot" light will still go out with this condition as the alternator is still supplying current BUT it just isn't enough for all the system demands of your power glutton "prancing horse."

I'd remove the alternator, as others have suggested, and have it bench checked for full output. A battery load meter is a handy tool to have and they can be had cheaply on eBay . . .

Best of luck!

Stuart

 

I just had the alternators on my BB512i rebuilt at a cost of $125.00 each. I had them add extra windings which increased their output from 55amps each to 70amps each. My car now runs better than it has since I have owned it. I was having the same battery going dead problem as you are now having.

 

KHayes - yes, the alternator can be extracted from the top. Yes, you must remove the narrow grill immediately behind the rear window. Yes, grill removal is easy - four 10 mm screws can be reached with hand and small box-end.

The tricky part is removing the alternator. On my 1986, you must remove the driver-side plenum. This is easy to do, and will give you all the room you need. I struggled for several hours trying to lift the alternator out without removing the plenum. Body work and engine parts are just where they need to be to prevent one from doing this. Take the plenum off and it is a breeze. Speaking of breezes, there is an air scoop that covers the alternator and directs airflow for cooling of the alternator. It must be removed with the alternator. Have fun.

Jim S.

 

1) Yes, you remove the little grill, but I had to remove the upper intake manifold as well to get the d@mn thing out of there.
You will find it very cramped to work in there.

There are threads on this R&R.

If you do it yourself, look at the parts manual first. There are little pieces that can fall out and drop into the lower manifold, namely the gasket joining the two has O rings in it that caught me by surprise because they were not shown in my parts manual.

2) Don't know what you have in there.
I believe original equipment was Bosch, but the replacement AC alternator is available everywhere, and can be rebuilt at alternator repair shop. If it's a Bosch, most just replace it with an AC, unless you want 100% original

 

Khayes - funny you should have melting of your headlight indicator light lense. Mine has done the same. Can one replace it? How did you go about getting to it, and inserting another?

Thanks.

Jim S.

 

Agreed! This was the exact same problem I had. Caused intermittent starting problems, so I just got new battery cables and bypassed the shut off switch entirely. Haven't had a problem since.