low idle voltage

[GetMeMyStogie]

I've noticed that for the last month or more, my volt gauge shows 10 volts when I'm at idle. If I put it in neutral, it jumps to 11 or so and then slowly makes its way just north of 12. I have no signs of hard starts yet, nor weird electrical issues while driving.

I figure it's either the battery or the alternator, but both were replaced a couple years ago. Battery from Ford, alternator from ebay (DB electrical 200 amp).

I'm too lazy to diagnose, so I'm wondering - can a bad battery cause this? I'm leaning toward no, so betting it's the alternator.

[fastblackmerc]

I've noticed that for the last month or more, my volt gauge shows 10 volts when I'm at idle. If I put it in neutral, it jumps to 11 or so and then slowly makes its way just north of 12. I have no signs of hard starts yet, nor weird electrical issues while driving.

I figure it's either the battery or the alternator, but both were replaced a couple years ago. Battery from Ford, alternator from ebay (DB electrical 200 amp).

I'm too lazy to diagnose, so I'm wondering - can a bad battery cause this? I'm leaning toward no, so betting it's the alternator.

Take it to a FLAPS or Sears and ask them to test the battery & alternator.

[Spectragod]

More than likely the alternator, I would charge the battery then check it (the battery) with a Midtronics and verify the state of health of the battery.

After that, load test the alternator. If the alternator is good, measure the voltage at the battery positve terminal and at the output of the alternator, if there is a difference in the voltage, you have a bad cable.

But I would start by trickle charging the battery overnight.

[RF Overlord]

Remember, the voltmeter in most cars is not a precision instrument. If your voltmeter is only reading "just north of 12" idling in neutral, that's low...it should be closer to 14. Verify it with a good VOM.

[justbob]

Mine used to do the same. I installed the Trilogy and spun that bad boy backwards and she's been 14 volts ever since LOL. But that is an expensive fix... Do what spectragod said ^


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[babbage]

Remember, the voltmeter in most cars is not a precision instrument. If your voltmeter is only reading "just north of 12" idling in neutral, that's low...it should be closer to 14. Verify it with a good VOM.

This is true too, I look at voltage via a Scangage 2 mounted on the left corner of dash.

I wonder if the OP has underdrives? You can bump your idle 100 rpm to spin the alt a bit faster.

[GetMeMyStogie]

No underdrives. Even though I'm looking at the stock gauge, I doubt that it's that inaccurate. A few tenths of a volt either way, sure... maybe even half a volt or so. But it's reading 10 when it ought to be 13 or even 14.

I'll try a voltmeter anyway, since it's the least amount of work :)

[justbob]

You would know for certain at night as your lights would dim way down.


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[Rockettman]

Yes the guage (although not great), WILL show a good drop and potential issue. The voltmeter really is the only way to "track things down" from that point on.

Let me know "GetMeMyStogie" if you need anything to help. I'm in T.O. too.
:beer:

[capt512]

Mine is that way also, replaced the battery and that helped a little, but still very much exists. My AC slows down a decent bit too if im idling like at a light, pretty noticeable. Have had my alternator checked but no luck.