so I had to jump start the car this morning ('66 dodge dart 270 with 225 electronic ignition, elect. voltage regulator, dual field alternator, starter from 96 dakota truck) and it turned on no problem.

Drove it into garage and disconnected battery.
the idle went up a bit (odd), but it kept running and did not shut off.
conclusion: battery not good, alternator doing its job.

I turned on the headlights and POP!! they blew out

what the heck?

is my regulator bad? Now I have to repalce headlights also (stupid) but I wanted to check to make sure alternator was putting out enough juice to power the perihperals. guess it was and then some.

So, what gives? regulator? is that why my battery was dead? When i jump started the car, I used a honda with a 1.3 Litre engine and a tiny battery, but it was enough. What do you guys think?

Caesar

Do not remove the battery cable from a running car. The battery can absorb a lot of power and if you disconnect the battery the electrical system voltage can spike very high and fry things like voltage regulators. The engine sped up because you removed most of the electrical load from the alternator which removed mechanical load from the engine. The regulator may or may not have been bad before removing the battery cable, but if you blew both headlights it's a fair bet that it's bad now.

Also your conclusion that the battery was bad may be erroneous. Something as simple as the tail lights not switching off or the dome light being on could have drained the battery. Not the battery's fault.

I think you cost yourself a few dollars unnecessarily.

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Joshua

An alternator can charge and still be bad. If it has a shorted diode, it will charge (not properly), but drain the battery when the engine is off. As stated by Joshie225, never, ever disconnect a battery from a running engine. It is bad for our older cars, but usually fatal on newer computer cars. It can let the "magic smoke" out of the electrical components.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The battery was not turning the car on at all. I checked all lights and everything was off when I parked the car, BOTH times when it decided not to start again.

So at it turns out I may have fried regulator. But alternator could not have been bad. I had it bench tested before I installed it on the car not two months ago, and it passed with flying colors.

Ignition module is good as car RUNs and runs well.

Just not enough juice to kick starter UNLESS i had it connected to another car via jumper cables.

I know the alternator can be bad and still charge, but it cant be bad AND still pass a bench test on a diagnostic machine either can it?

THe regulator was brand new also, bought it when I had the alternator bench tested.

The headlights were off both times I parked as was the dome light.
THe only thing I can think of is the parking brake light, but the wire is not connected to the switch at all, could it be grounding on the carpet somehow?

Caesar

OK. First, disconnect the battery cables, give the battery a full charge, and clean the battery posts, and cables. Make sure every thing is off, and the doors closed, connect the positive battery cable. Connect a test light from the neg battery post to the neg cable. If the light lites, you need to find what electrical item is on and draining the battery ( which can be anything, including the alternator, if it has a bad diode). If the light does not lite, connect the neg cable to the battery. Start the engine and measure the voltage at the battery terminals (should be over 13.4 volts up to 14.4 volts, at an engine speed over 1,000 rpm). If the voltage is not more than the voltage of the battery with the engine off, then disconnect the green wire from the alternator field connection, and ground the terminal of the alternator (do not ground the wire), with the engine running. If the voltage increases, above 13.8 volts the regulator is bad (this test bypased the regulator) or the green wire is broken, between the alt and the reg. If the voltage does not increase, it is a bad alternator or wiring. Check the voltage on the blue wire at the alt. With the key on, engine off, should be battery voltage. If not, it is a wiring problem, on the blue wire.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Nice Test Charrlie S
We ought to put a sticky here with this info and Ballast resistor also.
Thanks
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Some of the steps I posted, are specific to the Dual field wire alternator, with the late style electronic regulator (triangular plug). Some test are different for the early single field wire alternator and the rectangular regulator (mechanical or electronic). Original post stated an early (66 Dart) car, but with the late style charging system.

The easiest way to check a battery is either with a hydrometer, to check the specific gravity of the acid, or take it to a parts store for a good load test. Most auto hobyists do not have a good enough load tester.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Charrlie
I thought that hygrometers were almost obselete. Arnt most batterys sealed these days?
I see your point on the 2 different charging systems.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Most wet cell batteries, still have caps to check the level. Those "toaster" type load testers, only load a battery to about 100 amps. Will tell you the battery is bad, if it is really shot, but not if the battery is just barely bad.

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Charrlie, are you talking about one like this:

http://tinyurl.com/3dg96g

That would explain a lot. I had a battery that drove me nuts for a couple of years. I was too cheap to just buy one because it kept testing good but just when I needed it, it wouldn't start. It tested as good with a hydrometer also.

Danny

Yup Definitely correct on those "toaster" load testers, only I thought their applied load was even less! That is why I never even thought of selling my Snap on AVR (Their equiv to the old Sun VAT-40) when I got out of wrenching full time. As far as how big the engine in the jumper car was, that is no indication of how strong the battery or the amperage that its belt driven alternator adds to the available juice to crank over the dead vehicle.

That's the one, I'm talking about. About the only thing they will test is a lawn mower battery. If you are REALLY in a pinch, it is possible to use two of them together (put them in parallel). That will put double the load on the battery, and increase your chance of a valid test. But it is still more reliable to "bench test" (not in the car) the battery at a parts store, if you don't have a carbon pile load tester.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I will be testing the system this coming week. I am on break from school so I have some time. Thanks again.
Caesar