Bad alternator?

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robjkc

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I just got back from a little drive with my 64 Dart tonight. I haven't had it too long and took it for a drive on the highway.

It ran great while on the highway, but when I got back in town it wanted to die at each intersection. The oil light would come on and the voltage gauge would drop down towards D (discharging?). I had to put it in neutral and keep it reeved up at each intersection so it wouldn't die.

The other night a friend told me it was acting like it was running on the battery as the lights would get brighter when you gave it gas, but it didn't act this bad.

It's probably an easy fix and I'd give my friend a call but it's getting late so I thought I would see what you all thought.

If I do need to get a new alternator should I upgrade to a bigger unit?

Thanks for the help!
 
Sound like it's on it's way out, also could be a dead cell on the battery and when u got your foot on the gas the alternator is the only thing keeping the battery alive. I think the best idea is to pull the batter and get it check out first at a local auto store ( it's free at autozone i know) If the battery's good then put it back in and take the car and hook up a voltmeter to the alternator and see how much it's putting out. Hope this helps.
 
Another way to check your alternator, is start the car and pull the positive cable off the battery. If the car dies this is a sign of a bad alternator or a bad voltage regulator. I just had this happen to my Dart a few weeks ago.

How does your car run when the lights and all extra electrical things are off? I did this test and the car died so I took it over to the parts store and had them check the alternator, turned out it was OK and my voltage regulator was the culprit.

To answer the second part of your question, I won't put a bigger one in unless you are running a big stereo system or different headlights.
 
I had a similar problem and it was the amp gauge. The gauge had so much resistance that the car was running off only the battery.

Check voltage at battery and back of alternator when car is running if there is a large voltage drop between the two you may have same problem, it is common with these cars.
 
Well, my alternator and battery both checked out OK. I raised my idle a little to keep it from dying while in Drive. To keep it from dying I have it idling at about 650-700 rpm while in Drive, which means it idles at around 800 while in Neutral.

I hooked up a voltmeter to the battery and while idling in Neutral the voltage reads around 14.3 volts (with lights on). When I idle in Drive the voltmeter reads about 13 volts on the battery and my ammeter goes toward the "D" (Discharging). Once I switch it back to Neutral the voltage slowly goes back to 14.3 volts.

Is this drop in voltage while at the lower rpm normal or do I have an issue with the voltage regulator or something else? Thanks!
 
Did you try increasing your idle speed? Could just be that your engine was idling too low. Try setting your idle speed at 800-900 rpm while someone holds the brake and has the transmission in drive.
 
Another way to check your alternator, is start the car and pull the positive cable off the battery. If the car dies this is a sign of a bad alternator or a bad voltage regulator. I just had this happen to my Dart a few weeks ago.

How does your car run when the lights and all extra electrical things are off? I did this test and the car died so I took it over to the parts store and had them check the alternator, turned out it was OK and my voltage regulator was the culprit.

To answer the second part of your question, I won't put a bigger one in unless you are running a big stereo system or different headlights.

That doesn't always work and I had a electrican tell me never do that again or your'll create more problems than your looking for.
 
Well, my alternator and battery both checked out OK. I raised my idle a little to keep it from dying while in Drive. To keep it from dying I have it idling at about 650-700 rpm while in Drive, which means it idles at around 800 while in Neutral.

I hooked up a voltmeter to the battery and while idling in Neutral the voltage reads around 14.3 volts (with lights on). When I idle in Drive the voltmeter reads about 13 volts on the battery and my ammeter goes toward the "D" (Discharging). Once I switch it back to Neutral the voltage slowly goes back to 14.3 volts.

Is this drop in voltage while at the lower rpm normal or do I have an issue with the voltage regulator or something else? Thanks!


Yes, it is normal for a little alternator to go to a slight discharge o the gauge. BUT, as you just told us at idle it is still @ 13v. There is nothing wrong with 13v. when you consider the battery voltage is normally 12.5v. What happens when you increase the engine speed is the alternator is capable of putting out more amps. and there for charging the battery to the desired 14.2v. the regulator is designed to keep it at. These old cars have small alternators, usually around 30 to 40 amps. Plenty for a plane Jane car with no A/C or other options. It sounds fine to me. The dying is another problem! Carb. issue?
 
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