tegwin
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| posted on 6/2/08 at 12:36 PM |
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Headlights get brighter with revs
I have a pinto on standard ignition system and standard alternator...
If I put the headlights on and rev the engine the lights get brighter....
Is this an SVA fail?
I had assumed that the circuitry in the alternator would stop this from happening...
I suspect I have not wired something up properly....
Anyone have a wiring digram for the engine?
Specifically the alternator?
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dan__wright
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| posted on 6/2/08 at 12:38 PM |
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sounds like regulator is shot (check battery voltage)
FREE THE ROADSTER ONE…!!
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Mr Whippy
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| posted on 6/2/08 at 12:39 PM |
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no that’s perfectly normal, the alternator does not produce much charge at idle speeds, rev the engine and the systems voltage goes up and so does the
lights output.
That’s why it’s best to use fast idle to jump starting another car. Interestingly dynamos produce charge at very low speeds but can't take high
revs like an alternator.
[Edited on 6/2/08 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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MikeRJ
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| posted on 6/2/08 at 12:47 PM |
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It depends on if they get MUCH brighter. If so you might have a failed regulator in the alternator, measuring the battery voltage at a few thousand
RPM should tell you one way or the other (shouldn't be more than about 14.5v)
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Macbeast
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| posted on 6/2/08 at 01:00 PM |
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This could also be a symptom of a semi-discharged or knacked battery.
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onzarob
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| posted on 6/2/08 at 01:03 PM |
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quote:
Originally posted by Macbeast
This could also be a symptom of a semi-discharged or knacked battery.
second that, battery needs a good charge 
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tegwin
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| posted on 6/2/08 at 01:17 PM |
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Doesnt suprise me...lots of starting and stopping of the engine...
Will plug it in later and see if charging it will work.
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RazMan
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| posted on 6/2/08 at 01:55 PM |
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Could also be down to loose battery connections - the battery itself acts as a kind of regulator, absorbing the voltage peaks. As already mentioned,
check the voltage at the battery at rest. It should be around 12V at least if the battery is ok. Then start the engine and measure again - should be
around 13.5-14.0 at 2000rpm if everything is charging ok. Switching the headlights on will cause a voltage drop but as long as it stays above 12v
(ish) then all is well.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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dhutch
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| posted on 6/2/08 at 02:13 PM |
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Yeah, even a brand new production car will do that to some degree.
- I notice it espcially when reversing up our drive if i dip the revs below tickover the headlights go much dimmer. As well as geting brighter upto
around 2000rpm, where i levals off as the alternator has reached max charge.
You could messure the voltage. 14.8v is about as high as i would expect to see it.
- Its going above this there might be an issue with the alternator regulator overvolting (which will nacker the battery too over time).
- Then if its much below at tickover, it could be a problem with the battery being flat/wornout/small.
Daniel
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jammy_basturd
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| posted on 6/2/08 at 02:27 PM |
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Could also be the result of an incorrectly tensioned alternator belt.
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02GF74
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| posted on 6/2/08 at 02:32 PM |
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wot they say ^^^^
at idle it is possible for the alternator to not have reached itself-excited state so it is not throwing out power. The lights will be pwered by the
battery.
As you rev the engine, at some point it does, typically 1200 rpm, then you should see 13.5-14 V on the battery. The voltage should stay at that level
regardless of any higher rpm.
If you have much more than 14 V,. then you are gonna start burning out bulbs and boiling the battery, if Lead Acid - and means the regulator is shot.
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worX
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| posted on 6/2/08 at 03:03 PM |
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It all depends on how much brighter they go!
Steve
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britishtrident
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| posted on 6/2/08 at 03:38 PM |
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As already been said check the charging voltage -- engine running shouldn't ever be above 14.9 volts regardless of load or RPM.
Undler load (eg headlights & heater blower on) it shouldn't ever be under 13.4 at any rpm greater than 1500 or so.
Before testing it is adviseable to charge the battery until its shows at least 12.5 volts off charge.
Excess charging voltage can be caused by either a knckerd regulator or bad (eg arcing)) connection usually at the back of the alternator.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 6/2/08 at 03:48 PM |
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quote:
Originally posted by 02GF74
wot they say ^^^^
at idle it is possible for the alternator to not have reached itself-excited state so it is not throwing out power. The lights will be pwered by the
battery.
As you rev the engine, at some point it does, typically 1200 rpm, then you should see 13.5-14 V on the battery. The voltage should stay at that level
regardless of any higher rpm.
If you have much more than 14 V,. then you are gonna start burning out bulbs and boiling the battery, if Lead Acid - and means the regulator is shot.
Nearly all modern medium sized cars cars with high output alternators and hi-tech batteries charge just a whisker under 14.9 volts. Never over 15v
as above 15v car bulbs start to blow prematurely.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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02GF74
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| posted on 7/2/08 at 10:02 AM |
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quote:
Originally posted by britishtrident
Nearly all modern medium sized cars cars with high output alternators and hi-tech batteries charge just a whisker under 14.9 volts. Never over 15v
as above 15v car bulbs start to blow prematurely.
dunno since my most modern car is 14 years old this year. 
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britishtrident
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| posted on 8/2/08 at 03:58 PM |
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quote:
Originally posted by 02GF74
quote:
Originally posted by britishtrident
Nearly all modern medium sized cars cars with high output alternators and hi-tech batteries charge just a whisker under 14.9 volts. Never over 15v
as above 15v car bulbs start to blow prematurely.
dunno since my most modern car is 14 years old this year.
Strangely on 1950's 1960's car the DC dynamos charged at up to 15.1 volts after which the "cut-out" operated.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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