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Discussion Starter · #1 ·
I got bored and installed a voltmeter in my empty radio hole.

When my headlights are off, it's at the normal 12-12.5 volts, when the headlights are on it drops to 9.

My question - Is this normal? Will anyone even know the answer since no Escorts came with voltmeters? :)

::start Jeopardy theme::
 

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I assume that's with the car off. It should be a steady 14 when it's running. The headlights draw quite a bit so I guess a drop like that would be about normal if the car isn't running.
 

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Discussion Starter · #3 ·
Nope, car on, off, idling, revving, revlimiting, whatever. :)
I don't have any electrical problems with the car, but I didn't think this was normal, and if there IS something wrong, i want to get it taken care of before something bigger happens.
 

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Battery voltage with the engine running shold be between 13 and 14v. You require between 1 to 2 volts above normal battery voltage for it to charge properly. If you experience voltage drops when you turn your lights on or use a lot of electrical stuff at once, your voltage regulator is not functioning properly.

What specificly in the vehicle did you wire the meter to? Is it fed directly from the battery?

Matt 8)
 

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Discussion Starter · #5 ·
The power wire that used to connect to my radio.

There is nothing to draw power from the alternator other than the headlights. I no longer have a radio, cruise, AC, no power windows, no power door locks, nothing.

I'm weirded out..

I'm guessing the voltage reg. is built into the alternator?
 

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well when i bought my escort i had the same thing, went from 12 to 9 or from 14 to about 12 or so, i bought a new battery thinking that was the problem but no, it still does it, my freind hooked a volt meter to his 72 mustang, and it did the same thing, so i dont know, i just said F it, and left it alone, let me know what you find out about it, if you find anything,
-Jim
 

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TitoElSpicco said:
I got bored and installed a voltmeter in my empty radio hole.

When my headlights are off, it's at the normal 12-12.5 volts, when the headlights are on it drops to 9.
My voltmeter (pictured earlier in this thread) dropped from about 13.1V to about 12.9 volts this morning when I turned in the headlights before I started the engine. I was doing this test as per your request, I normally do not have headlights on when starting the engine! And my voltmeter is also wired into the radio circuit. I say verify voltage with another voltmeter across the battery terminals.
 

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TitoElSpicco said:
The power wire that used to connect to my radio.

There is nothing to draw power from the alternator other than the headlights. I no longer have a radio, cruise, AC, no power windows, no power door locks, nothing.

I'm weirded out..

I'm guessing the voltage reg. is built into the alternator?
headlights dont draw power from the alternator. They draw from the battery. 13.5 - 14 volts is what you should read. If not you might have a failing battery on you. You might have something hooked up wrong or something. Think about it. If you once had a radio in that spot and i'm sure you had your headlights on w/ your radio on at one point. And since a radio runs on 12 volts...then the radio wouldnt have turned on or would have cut out when u flipped on ur headlights. There is a problem somewhere. Maybe the voltimeter....not a good ground on it...somthing throwing off the reading. I tested mine and i went from 13.6 to 12.1 when i flipped on my headlights w/ the car on

And yes...the voltage regulator is built into the alternator.
 

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92gt5spd said:
headlights dont draw power from the alternator. They draw from the battery. 13.5 - 14 volts is what you should read. If not you might have a failing battery on you. You might have something hooked up wrong or something. Think about it. If you once had a radio in that spot and i'm sure you had your headlights on w/ your radio on at one point. And since a radio runs on 12 volts...then the radio wouldnt have turned on or would have cut out when u flipped on ur headlights.
^ Wrong.

When the alternator is working, ALL power is pulled from the alternator first, untill the voltage is pulled below 12 ( at that point the alternator is at full load) than the remaining power is pulled from the battery.

If your head lights some how pulled power from the battery and not the alternator you would have a dead battery in a matter of time.

Most stock and aftermarket radios have a operating voltage range from 9-16 volts. So it's not gonna cut out from the draw from the head lights.
 

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I updated my previous post with voltage level 13.1 -> 12.9 when I turned my headlights on, not the previous 13.9 -> 12.9

My battery isn't going to be at 13.9V in the morning after sitting all night.
 

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If you put a heavier ground from the body to the battery it will be higher. You are probally grounded very good to the motor and the battery will charge properly. But the line to the rest of the car is not adacuate. It is a very common thing on most cars. And is why most car audio enthusious will put so many grounds on there cars so they get proper voltage.
 

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jon91156 said:
If you put a heavier ground from the body to the battery it will be higher. You are probally grounded very good to the motor and the battery will charge properly. But the line to the rest of the car is not adacuate. It is a very common thing on most cars.
Word. And yes, voltage regulation is taken care of inside the alternator.
 

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Have you checked the voltage actoss the battery terminals to verify that it's really that much of a voltage drop?

I'm thinking that if your voltage really is dipping that much then either your battery sucks or you have a bad connection someplace.
 

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Jeffescortlx said:
92gt5spd said:
headlights dont draw power from the alternator. They draw from the battery. 13.5 - 14 volts is what you should read. If not you might have a failing battery on you. You might have something hooked up wrong or something. Think about it. If you once had a radio in that spot and i'm sure you had your headlights on w/ your radio on at one point. And since a radio runs on 12 volts...then the radio wouldnt have turned on or would have cut out when u flipped on ur headlights.
^ Wrong.

When the alternator is working, ALL power is pulled from the alternator first, untill the voltage is pulled below 12 ( at that point the alternator is at full load) than the remaining power is pulled from the battery.

If your head lights some how pulled power from the battery and not the alternator you would have a dead battery in a matter of time.

Most stock and aftermarket radios have a operating voltage range from 9-16 volts. So it's not gonna cut out from the draw from the head lights.
NOT wrong... Thats what the VOLTAGE regulator on the damn alternator is for. ALSO...YOU go get a 9 volt battery and run your radio off of it.....CUZ it dont work. In my spare time i fix radios and i'm an EET major, so i know a shitload about electronics. I have a lot of variable power supplies and stuff and it wont run on 9 volts. And the reason it still works w/ a 14 volt battery is because of regulator circuits inside of all that wiring under the dash. Look up the diagram for your headlight wiring and see where it runs in to.
 

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Discussion Starter · #17 ·
UPDATE - I was racing a friend in an S2k last night, at night, hit my rev limiter rather firmly in both first and second gear, and after the race I noticed my voltage with my headlights on had jumps from 9 to 10.5. Now, that being said, I'm just as dumbfounded as before. :) Just letting you know.

jon91156 said:
If you put a heavier ground from the body to the battery it will be higher.
zzyzzx said:
Have you checked the voltage actoss the battery terminals to verify that it's really that much of a voltage drop?

I'm thinking that if your voltage really is dipping that much then either your battery sucks or you have a bad connection someplace.
THE CAR RUNS OFF OF THE ALTERNATOR ALONE WHILE THE ENGINE IS RUNNING. THE BATTERY HAS ABSOLUTELY NOTHING TO DO WITH ANYTHING. IF I TAKE THE BATTERY OUT OF THE CAR AND RUN THE CAR AROUND TOWN WITH THE HEADLIGHTS ON, I GET THE SAME EXACT READINGS.
The engine cranks at a perfectly normal speed, and the battery is only 2-3 months old. There is nothing wrong with the battery. TRUST ME.

92gt5spd - My radio obviously was strangly working off of 9 volts since that's what the radio was getting when the headlights were on. (I have the voltometer hooked up to the radio constant power wire). What he was telling you you were wrong about is that something draws power from the battery when the car is operating. I can start my car, TAKE THE BATTERY OUT of the car, and everything works just like it does while its in. No hesitation, the lights don't even get any dimmer. The voltometer doesn't change at all, nothing happens. Once the car has started and the key is returned to "run" instead of "start" every single volt of power should come from the alternator (which mine does). I was just anaware is was such a low #.
 

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then maybe something wrong w/ ur alternator. Because it seriously should be running above 12 volts while the car is on.

Seeing as how the alternator is in circuit w/ the battery, if the battery is removed, then the alternator would take over and handle it. But when the battery is in the car, all voltage is taken from the battery. Think about it...The battery is like a reservoir the only thing that will happen if you pull alot is that it will drain faster. However, the alternator is not. If you run everythiing off the alternator(which is just a generator) you risk pulling more power than the alternator can generate at one time. Thats why it only makes sense to pull power from your reservoir and have ur alternator refilling it. Think about it for a second. If you have a booming system hooked up to the battery and you were blaring it. And if everything ran off of the alternator while the car was on, then the headlights would not dim.
So...battery is used as the primary source while the car is on and off....alternator is used to recharge it and if no battery is present, to run everything.
 

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Please don't disconnect the battery while the car is running!

You need it when it's running because it takes the place of the capacitor that a normal DC power supply would have!
 

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zzyzzx said:
Please don't disconnect the battery while the car is running!

You need it when it's running because it takes the place of the capacitor that a normal DC power supply would have!
And finally someone else at this site agrees w/ me. THANKYOU!
That was what i was trying to explain in the "reservoir" analogy, which is what a capacitor is. If ya didnt have the battery, every surge would go to the alternator causing it to burn up.
 
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