Electrical Issue.... Alternator????

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Electrical Issue.... Alternator????

Postby bugdewde » Sat May 31, 2014 1:26 pm

First off, I've driven Vegas, in various driveline configurations, for many thousands of miles over the last 20 years. I've never had to be towed in a Vega before.... until last night.
Towed Vega.jpeg


Background:
My mostly stock '73 has a swapped in HEI distributor by the previous owner... been like that since the '70's, probably.
The alternator is from my old parts car that sat in a junkyard for 20 years (been installed for a couple years now).
I've had a battery drain for the last few months. Not bad enough to do anything about it. If it sat for 4 or 5 days, the battery would be too low to crank... hindsight now has me thinking I shouldn't be so lazy.

I charged the battery yesterday for an hour or so with 50 amps. Got the car running and headed out for a 40 mile trip to Knoxville. Made it about 10 miles. Running 80 on the interstate, it just died. Got fuel, as the accelerator pump squirted fuel, but after 2 attempts at starting, the battery got too low to crank.

After calling a ride, I took a battery booster pack with me back to the car, suspecting an electrical issue..... :wink:
It got the car started enough to get it driven up on the trailer.
I've unloaded the car in my basement now, and I'm trying to get enough juice to start the engine to test the alternator.... what am I looking for?

I seem to remember there used to be a magnet on the back-side of the alternator that would indicate it was charging, but what voltage should I be seeing with a multi-meter? (I'm not too lazy to google it, just curious what you guys might think the issue might be?)

Does the ignition module and/or coil ever go hit or miss? Maybe dies with heat? Cools down and works until hot again? ????

Could it just be a bad battery?

Then there's that stupid, annoying battery drain issue..... I hate troubleshooting electrical..... I know, start pulling fuses until I find the culprit circuit, then narrow it down from there.

But this dying at 80 mph and leaving me on the side of the road is the real kicker, now. Never had that happen before. :think:
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Re: Electrical Issue.... Alternator????

Postby bugdewde » Sat May 31, 2014 1:58 pm

bugdewde wrote:
But this dying at 80 mph and leaving me on the side of the road is the real kicker, now. Never had that happen before. :think:


OK..... you're not going to believe this...... I was out of fuel!!!! :oops:

Initial testing didn't get any magnetic pull on back of alternator.... not sure if this one does it or not. Just a few seconds(15) after I unhooked the battery charger (50 amps) it died. It's gotta be the alternator, I think.

Just out of curiosity, I checked the accelerator pump for squirting fuel.... nope! It's out of gas!!!

OK... but that still doesn't fix the electrical drain.... back to the drawing board. God, I hate pulling fuses and troubleshooting electrical gremlins.... the first 2 glass fuses I pulled broke..... :censored:
Now, my cheap multi-meter has died, too.... I left the on switch on last night. Dead battery!!!
REALLY!
Dwight

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'73 Vega Wagon - Currently in Limbo....
My rides: http://www.cardomain.com/id/bugdewde
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Re: Electrical Issue.... Alternator????

Postby Monza Harry » Sat May 31, 2014 2:24 pm

Hey Dwight, instead of using your multi-meter use an old 194 bulb with the socket (pigtail) as this will show you if there is a current draw. You will usually get a voltage but not necessarily a relevant current ie: the radio may show voltage (showing a connection to ground) but that is/maybe the clock, which will take about two years or longer to kill the battery, the clock's draw is so low that it won't even come close to lighting the 194 bulb. I take a screwdriver and carefully pry the fuses sideways to make sure they haven't "hooked up" with the fuse panel then use my puller. I suspect that your slow drain will show up as corrosion (or a pinched/pierced wire) on a "Bat" circuit. I would start with under hood first, corrosion at the alt, battery, or starter, big wire with full time power, I have seen a battery almost killed with grinding dust in the bat. slim caused a slow bleed right across the top of the bat. washed the bat. and no more slow cranking, then if that doesn't solve the problem I would start at the interior light, then head light switch, then ignition sw. I wouldn't rule out the fuse panel as they can get wet and develop "issues". Just my 5 cents (inflation has ruined everything) Harry
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Re: Electrical Issue.... Alternator????

Postby bugdewde » Sat May 31, 2014 2:52 pm

Thanks for the tips, Harry. I'm done, now. Huge thunder storm rolling through. I had to remove the Vega from the basement to put the T/A inside if it hails.
Poor old Vega has been a trooper and deserves a nice inside storage place.....

Good idea on the fuses sticking.... I bet some of them haven't moved in 40 years.
194 bulb... I think I have a couple of them ... like side marker or instrument light bulbs?
Dwight

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Re: Electrical Issue.... Alternator????

Postby marco_1978_spyder » Sat May 31, 2014 4:44 pm

This may be unrelated, but I had a battery drain..it was the Door open/key on Chime thing. It was sitting their warm to the touch for no reason. I checked the circuit and sure enough that was it.
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Re: Electrical Issue.... Alternator????

Postby cosvega76 » Sun Jun 01, 2014 8:12 am

Dwight,

When the alternator is charging, you should see a voltmeter reading at the battery of 13.5-14.2 volts. If it is charging, the rotor will have current going through it, so the rear bearing will have magnetism.

But since you've been complaining of a draw, my guess is that you have a diode in the alternator that has failed, more than likely in the rectifier bridge. There are two components in the alternator that have diodes: the diode trio and the rectifier bridge. With the halves of the alternator separated, the diode trio is the small component that connects between the brush holder and the rectifier bridge, and the rectifier bridge is the rather large component that is attached to the rear frame of the alternator that the positive terminal attaches to.

You can use an ohmmeter to check the diodes. With the leads attached one direction there should be a smaller amount of resistance, reversing the leads will show a large amount of resistance. If you have one or more that don't show much difference with the leads reversed (especially a low amount of resistance), that would be the failed diode.

Parts should still be available at the auto parts store.


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Re: Electrical Issue.... Alternator????

Postby Monza Harry » Sun Jun 01, 2014 7:16 pm

Dwight Yes on the side marker bulb, a 194 is about 4W, so that would be 1/3 of an amp. that would take about 210 hour to deplete a 70 amp/hr. battery (average medium car bat IIRC). The component would have to be drawing more than the light bulb for this to work, therefore a real problem not some 0.1 amp draw like a clock or LED.Yes Marco exactly that is possible like I said about "corrosion" probably should have included component failure. And to add to Chucks post I would just unplug the alt. and check back in a day or two, check battery voltage before and after, that should eliminate or confirm that component in a hurry with almost no work. If confirmed Chuck is leading you done the right path, you may want to do the bearings and brushes at the same time, and then it is a "Re-Built" Alt. Hope this helps out! Harry
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