Lights Dim with the gas

my66coupe

Founding Member
Apr 30, 2002
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Arizona fountain hills
Ok I have this cheapo battery that I have used regularly, and when I rev it in park, the headlights stay the same. I now have this used optima in my car, and when I rev it in park the lights will go bright and when I let off, they will get lighter. I have a new alternator in the car also. What gives?

Mike
 
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my66coupe said:
Ok I have this cheapo battery that I have used regularly, and when I rev it in park, the headlights stay the same. I now have this used optima in my car, and when I rev it in park the lights will go bright and when I let off, they will get lighter. I have a new alternator in the car also. What gives?

Mike

Regulator problem
 
What kind of lights, and how many amp output of the alternator. My Stang does the same thing with a stock alternator and newer halogen type lights. Many articles have been written on this subject in magazines. I think mine is the alternator not being able to handle the load when the lights are turned on. My voltmeter shows 14 volts with motor at idle, but dips down to 13 when I turn on the headlights. Reving up the idle brings the voltage back to 14 with the headlights on.
 
my66coupe said:
Sorry I found that hard to word, they go brighter when I rev it up, and when I get off the gas, the lights dim down, lower, "lighter".

Mike

It still sounds like the regulator. But you can check the battery with a hydrometer and a volt meter to see if any of the cells are dead or shorted out. Also, sometimes the starter will short out & put a constant drain on the battery.
 
I would think the plug that goes to your voltage regulator could be dirty from years of oxidation. Get a spray can of electrical contact cleaner and spray the metal tabs inside your wiring plug, then see how it does. If that doesnt work, then I am thinking your headlight switch is on its way out.


stupid me forgot to mention that the fan belt that drives your alternator may be loose, check it for play.