Is there such a thing as a low RPM alternator

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Mopar to ya

Mopar to ya

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Like most of us, my Dart voltage drops below 12 volts at idle, but runs 14-15 at cruising speed. is there such a thing as an alternator that is designed to work at full capacity at lower rpms, or is there something else I can do? I do not use the factory ammeter. I disconnected it and connected both the wires together when I installed my custom dash and voltmeter. It's never been a problem, but I hate seeing such low voltage at idle.
 
Alternators do vary. Buying a larger output (amperage) is not necessarily better for lower RPM. In fact, in some cases, lower output alternators put out more at low RPM than the larger model.

Really, the only way to know for sure is to "find" (good luck) the engineering specs. Years ago, we actually had some Delco books which had graphs of shaft RPM vs output.

Generally, in "stock" Mopars, the squarebacks are better.

I don't know about the newer Denso, other stuff. I've been told some of the Ford alternators are very good.

You will NOT, however, find one that puts out "full capacity" at low RPM.

What are you running for idle speed, pulleys? IE small crank pulley? large alternator pulley? How about your loads? You running electric fans?
 
How good are your grounds? Whats the quality of the voltage regulator? Correct alternator pulley size?
 
Grounds are good. Standard pulleys. I am not looking for full capacity at idle, but it should not be 10 volts. The vehicle is discharging at idle. I would think 12 volts should be an absolute bare minimum. My modern cars don't get below 13 volts.
 
I would think a touch/bit smaller pulley will achieve a faster spin on the alternator Mopar to ya, I agree, a discharge at idle is a problem that needs to
be looked into, have you double checked your Volt meter to make sure it is accurate ?
 
I installed a denso alt on my '69 and it put's out 14 volts at idle with blower motor on high and headlights on!
 

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Smaller pulley for more RPM, be careful of top rpm speed.

The denso's work well.
 
One thing I forgot to mention is, it's very possible that your present alternator is not up to par. It could have damage to one or more diodes, the stator, or it could be a typical so called "rebuilt" which might have a mismatch of rotor and other parts..
 
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