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air conditioner or defrost on?
auto or manual climate control?
 

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Could be your fan kicking on. Mine does the same thing

Joe
 

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LUCA BRAZZI said:
My 94 T-Bird has a new problem...

At Idle... the voltage will dip sharply... then come back to normal... then dip again/etc

Voltage Regulator? Alternator? Something else?
Dip sharply as in 6V? ...2V? ?? We need more info/voltages to be much help other than guessing...
 

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I know when my fan or A/C compressor kick on the lights barely flicker enough to be noticed. Is it like that or like close engine stalling bad?
 

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Mine does it when the fan comes on. The lights dim too.
 

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If it’s just a little bit, I wouldn’t worry about it. Like if it clears up at 700-800rpm its prob normal for an aging vehicle. All of my vehicles will dip some voltage with a bunch accessories being turned on and off at idle. Our motors have a pretty low idle stock so it’s probably normal. My old truck won’t get to 14 volts until like 1,300rpm with all my accessories on, but that’s not normal lol.

When was the last time u changed your spark plugs? I know that if they are gapped too big from wear it will suck up a lot of power to light them off, and the alternator isn’t at full capacity at idle so that could help. My sisters Neon plugs gap were at least .100” when I replaced them. Ran A LOT better lol, and no dimming.
 

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Discussion Starter · #10 ·
From the gauge it looks like its dipping about 5 volts or so... I havent been able to pinpoint any device kicking on when it happens. It occurs whether or not the AC or heat is on. Its also accompanied by a feeling of hesitation in the engine. Ive recently replaced the IAC but the problem didnt start happening then.
 

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Gcline said:
I know when my fan or A/C compressor kick on the lights barely flicker enough to be noticed. Is it like that or like close engine stalling bad?
If it is stalling then I would worry about it. Chances are the fan motor can be going bad. When the motor fails it will cause a short that can stall your engine at idle. With a 2 speed fan usually the low speed fails first... :eek:
 

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Sounds like you may have an alternator problem. Have you taken it anywhere to have the system tested? I think places like Autozone etc do it free or close to it...
 

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Fluctuations in the gauge during window operation even turn signal use is commonplace. Ignore it.
 

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I have a very similar situation. No correlation to any item switchin on or off that I can tell. Sudden drops of 2V or so with quick (but not sudden) restoration to normal. Happens primarily at idle. Not concerned but very curious.

This is about triple the amount of fluctuation you get when you try to force the windows up when they are already up. As I said the needle drop is instantaneous. The rise (once it starts) can take 1/2 second to 1 second.
 

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my car does the same thing, if i turn on the lights the voltage drops on the meter, if i turn my turnsignals on, the voltage meter will bouce back and fourth with the turn signal.(like when the signal flashes the volts will drop, when it dosent the volts rise again), basicly if i turn anything on the volts will drop and my headlights wil dim when something is turned on, i was thinking about replacing the altonator since it hasnt been replaced since who know when
 
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