Voltage dropping below 13...Altenator Trouble??
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From: Bethesda, MD
Voltage dropping below 13...Altenator Trouble?? Until the last couple weeks, the voltage would start out high; probably 15 - 16 range and gradually reduce to just above 13. The needle always stayed to the right of the 13, generally with a small space visible between the 13 and needle.
Now, after the car has been running for a while (15 -20 minutes or more), the voltage has been dropping to 13 or slightly below recently. Yesterday, my voltage dropped to under 13 and there was a small space between the needle and the 13, so I'm guessing it was down to 12.6 - 12.8. This occured while I was driving so, my rpms were consistently 1400 or higher.
Other related info:
I do have an ASP pulley, but my warm idle is 1000 rpm.
The battery is only a few months old.
The last I saw my voltage drop below 13 was when I was bolt-on and put the ASP pulley on and my idle was 550 rpm. since the time when I raised the idle to 800 or higher, I have never seen it go below 13 volts.
Is this an altenator problem, voltage regulator, or something else?
Now, after the car has been running for a while (15 -20 minutes or more), the voltage has been dropping to 13 or slightly below recently. Yesterday, my voltage dropped to under 13 and there was a small space between the needle and the 13, so I'm guessing it was down to 12.6 - 12.8. This occured while I was driving so, my rpms were consistently 1400 or higher.
Other related info:
I do have an ASP pulley, but my warm idle is 1000 rpm.
The battery is only a few months old.
The last I saw my voltage drop below 13 was when I was bolt-on and put the ASP pulley on and my idle was 550 rpm. since the time when I raised the idle to 800 or higher, I have never seen it go below 13 volts.
Is this an altenator problem, voltage regulator, or something else?
Thread Starter
TECH Senior Member
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From: Bethesda, MD
Re: Voltage dropping below 13...Altenator Trouble?? guage. I've had the car for several years so I'm concerned by the change in the relative location and less concerned about the absolute reading.
TECH Enthusiast
Joined: Nov 2001
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From: Richmond, Va
Re: Voltage dropping below 13...Altenator Trouble?? Do the headlights dim and brighten with the readings? If so, then the gauge is accurate. I will say that out of the 4 chevies ive had, ive replaced the voltage regulator in each of them at least twice. 15 dollar part, only takes 20 mins to do after you have the alternator out. Use two toothpicks (or small allen wrenchs) to hold the brushes out of the way when you re-assemble it. Piece of cake.
Re: Voltage dropping below 13...Altenator Trouble?? Just go to an autozone and they have a machine and it takes 5 mins to test your alternator and battery on the car for free.
dunno if o'reily has the same thing or not.
dunno if o'reily has the same thing or not.
Re: Voltage dropping below 13...Altenator Trouble?? You should never see 15-16V; this is a pretty
sure sign the regulator is not really regulating.
However, it could also be showing you an ohmic
voltage rise between source voltage and sense
line (which is the point of regulation) under
high load current. You might work over the
connections, clean & tighten the terminal stud
etc. Ground differences between block and chassis
might also play. It's an old enough car that
you could be having some terminal and connector
crustification to get rid of.
sure sign the regulator is not really regulating.
However, it could also be showing you an ohmic
voltage rise between source voltage and sense
line (which is the point of regulation) under
high load current. You might work over the
connections, clean & tighten the terminal stud
etc. Ground differences between block and chassis
might also play. It's an old enough car that
you could be having some terminal and connector
crustification to get rid of.
Re: Voltage dropping below 13...Altenator Trouble?? I'd clean the connections.
If your regulator/ alternator is dying, you'd see some extreme fluctuations from like 10 to 17. It would cycle rapidly, and the lights might flicker.
If your regulator/ alternator is dying, you'd see some extreme fluctuations from like 10 to 17. It would cycle rapidly, and the lights might flicker.
Thread Starter
TECH Senior Member
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From: Bethesda, MD
Re: Voltage dropping below 13...Altenator Trouble?? Tested the altenator and it was fine. Put it back in and the voltage seems to be doing better so it appears to have been a connection issue.
I'll keep an eye on it. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
I'll keep an eye on it. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
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On The Tree
Joined: Nov 2002
Posts: 115
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From: Corpus Christi Texas
Re: Voltage dropping below 13...Altenator Trouble?? The previous F-body regulator/alternator had 3 diodes (or some other means of regulating the voltage), so when the first one failed the second one would burn out about a week later and then the third one about ten minutes after the second. The gauge voltage would step down in 1 1/2 volt increments for each failure. If this is still true you have about a week of mobility.
