Voltage Drop Question - Team Camaro Tech
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post #1 of 11 (permalink) Old Feb 24th, 09, 10:23 PM Thread Starter
George
 
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Voltage Drop Question

I have a '67 with a 327. I am running a stock alternator with an external regulator. The car starts and runs fine. The voltage at the battery and at the alternator is about 14.8-15.2. After the car "warms up", if I turn on the headlights, the voltage drops to 12.5 and increases in accelleration to over 15.

Other than the obvious, the alternator or regulator, what else should I look at.

Any help is appreciated.

Thanks

George
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post #2 of 11 (permalink) Old Feb 24th, 09, 10:32 PM Thread Starter
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Re: Voltage Drop Question

Moderator, please move this to the electrical forum, I just realized I shoudl have posted it there.
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post #3 of 11 (permalink) Old Feb 25th, 09, 05:15 AM
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Re: Voltage Drop Question

That's fairly normal operation for a smaller alternator. It simply doesn't have the power to put out full voltage into the system at that load and rpm. As you increase the rpm, it is able to produce more power.

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post #4 of 11 (permalink) Old Feb 25th, 09, 11:58 AM Thread Starter
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Re: Voltage Drop Question

Thanks for the info. Another thing I noticed is that my volt meter on my gauge cluster has a tic-toc (pulsating) effect when I use my turn signals. is this something I should be worried about?
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post #5 of 11 (permalink) Old Feb 25th, 09, 12:42 PM
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Re: Voltage Drop Question

A basic test for a faulty alternator, or an alternator that is too small for the application, is to idle the car about 100 rpms above idle, and warm up the car to give it time to fully charge that battery, then turn on everything, wipers, lights, indicators , radio, heater fan.
This in effect 'reproduces' a dark cold wet night turning a cnr.
The alternator should not go into -ve.

A 64 amp rated alternator will just marginally scrape thru the test...which is ok... a marginal -ve is ok but becomes +ve if rpms are around the 30 mph mark.

Low voltage can be due to
1/ a crook cell in the battery, check each cell with a hydrometer...not looking at the marker but looking for a cell that is quite different from the rest.
2/Worn bearings in the alternater...cheap easy fix
3/ worn accumiator/bushes...cheap easy fix...a strip of fine emery paper, wound around, a leather boot strape wound around and pull the ends to spin the emery paper.
4/A crook diode in the alternater...checked with an ohm meter, and replace, but more fiddlely with the soldering iron.

My Spelling is not incorrect...it is creative

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post #6 of 11 (permalink) Old Feb 25th, 09, 12:51 PM
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Re: Voltage Drop Question

Quote:
Originally Posted by ggonzalez View Post
is this something I should be worried about?
Normal indication.

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post #7 of 11 (permalink) Old Feb 25th, 09, 01:04 PM Thread Starter
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Re: Voltage Drop Question

Thanks, you guys are great. I just signed up for this site although I am now on my 3rd 1st gen Camaro (1 '69 and 2 '67s). Wish I would have looked for you guys years ago.
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post #8 of 11 (permalink) Old Feb 25th, 09, 07:04 PM
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Re: Voltage Drop Question

Agree completely with the others. I have a 61 amo factory alternator, and it will not hold 14 volts at idle with the lights on. Also has the tic toc when the turn signals are on. Never a problem tho. Battery is always charged, car always starts. 500 watts stereo, electronic fuel injection, and electric fuel pump are not bothered by it.





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post #9 of 11 (permalink) Old Feb 26th, 09, 01:43 AM
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Re: Voltage Drop Question

61 amp alternator Jim, I do think its time to retire that one and upgrade.
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post #10 of 11 (permalink) Old Feb 26th, 09, 12:24 PM
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Re: Voltage Drop Question

Quote:
61 amp alternator Jim, I do think its time to retire that one and upgrade.
Why ? "it will not hold 14 volts at idle with the lights on."
The only time Jim will run into a problem is if he is sitting at an insersection at night in heavy rain with sterio on for an hr or so, then parks the car up, without any incrase in the rpms off idle It may turn over but not fire next morning...and the likely hood of that happening is very slim....so why fix something that is not broke?

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post #11 of 11 (permalink) Old Feb 26th, 09, 12:52 PM Thread Starter
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Re: Voltage Drop Question

I got Jim beat, I'm running a 55 amp! I guess that would explain the results I'm seeing. I'm with Steptoe though, now that I know its not a problem, I wont mess with it. Besides, I live in Ca, where its doesnt rain much and I dont do much night driving with this car anyway!
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