Dim lights at idle on 68 - Vintage Mustang Forums
 
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post #1 of 14 (permalink) Old 05-23-2003, 10:22 PM Thread Starter
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With the headlights on & idling the headlights & dash lights are dim. As soon as I press the gas pedal they get bright. Is this the altenator or what?
Thanks in advance.
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post #2 of 14 (permalink) Old 05-23-2003, 10:27 PM
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That's probably normal for a stock alternator. Their output is not what todays high output alternators are. Just make sure your belt is tight, but it probably, as said, is normal. I simply means that at idle speed, the alternator output is lower than the battery draw, thus the lights dim until the engine/alternator is sped up.
Tom
I wouldn't worry about it.

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post #3 of 14 (permalink) Old 05-23-2003, 11:10 PM
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Yeah, just idle 'er up to 1,200rpm, problem solved, LOL.
You might try cleaning all the connectors sending volts to those lights though, might knock out enough resistance to make a difference.


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post #4 of 14 (permalink) Old 05-23-2003, 11:22 PM
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It's possible over time stop and go driving in conjunction with an old charging system could leave the battery a bit flat.....maybe you could trickle charge it for a while before driving it at night and see if it acts the same?

Ported vacuum IS manifold vacuum ANYTIME the throttle is open on a holley.
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post #5 of 14 (permalink) Old 05-24-2003, 12:52 AM
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its normal if you ask me, mine has always done it since the day i got it and others do the same.

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post #6 of 14 (permalink) Old 05-24-2003, 01:09 AM
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I changed my regulator for an electronic style and it helped a lot with the dimming of lights at idle.

Dave
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post #7 of 14 (permalink) Old 05-24-2003, 01:24 AM
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The 68 alternators were designed to put out 40 amps. The 87-on up alternators put out anywhere from 75-130 depending of the year. Here is some info on how you might be able to get a more powerful alternator put on your 68.
http://www.ronmorrisperformance.com/...ess/altern.htm
post #8 of 14 (permalink) Old 05-24-2003, 01:36 AM
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sounds normal upgrade the alternator
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post #9 of 14 (permalink) Old 05-24-2003, 01:44 AM
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wore out brushes
post #10 of 14 (permalink) Old 05-24-2003, 02:05 AM
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post #11 of 14 (permalink) Old 05-24-2003, 06:17 AM
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Quote:
wore out brushes
Brushes Alteranators don't use brushes. Just generators. Jeez!
post #12 of 14 (permalink) Old 05-24-2003, 08:38 AM
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if you have a voltmeter measure voltage at battery terminals with engine running - should be 13.5 to 14.5 Vs. your fan belt might be loose or if you have special racing type alt it may give you that condition. do not overtighten alt belt or you will possibly damage alt or water pump bearings. PM me if questions.

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post #13 of 14 (permalink) Old 05-24-2003, 08:42 AM
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That was a great site Sacbill led me to.
My '67's dash lights would dim then go out completely at idle. Then the headlights would dim, they would flicker at high beam, and the tail lights would dim.
I fixed both by new 100 amp alternator and new Optima battery. Now I can listen to the radio at red lights without the car running out of juice and stopping
I am going to check my voltage at the back of the lights to see If i need that relay from that red light as soon as I get my car back from the shop.
Gordy

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post #14 of 14 (permalink) Old 05-24-2003, 11:55 AM
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Quote:
Brushes Alteranators don't use brushes. Just generators. Jeez!
REALLY? Then how do you think the (rotating)field windings get engergized Take an alt. apart, yes you will find "brushes". They last a lot longer in an alt. because they only have to carry the light current to magnatize the field windings, instead of carrying the heavy output current as in a generator. So most people probably never have had to service them.

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