# battery light on 'till revved



## gmags (May 3, 2001)

my batter light on my 91 gti stays on in the morning until i rev the engine to about 1200 rpm. i changed the regulator, but still the same...any ideas?


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## deadguy (Apr 13, 2001)

*Re: battery light on 'till revved (gmags)*

Do you mean you changed the alternator? That would be my guess if not.


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## Stephen Webb (Apr 12, 2001)

*Re: battery light on 'till revved (gmags)*

quote:[HR][/HR]my batter light on my 91 gti stays on in the morning until i rev the engine to about 1200 rpm. i changed the regulator, but still the same...any ideas?[HR][/HR]​If the light stays out once you rev it past 1200 RPM, it's completely normal.
I don't know all the details of the difference between an alternator and a generator, but one thing is that the alternator has to be spun fast on startup until it becomes "self exciting", and then it can then charge at lower RPM.
Every VW I've had (except the Beetle which used a generator) exhibited this type of behavior to some extent. 
-Steve


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## spitpilot (Feb 14, 2000)

*Re: battery light on 'till revved (Stephen Webb)*

I had charging probs on my '81 Cab and after replacing alternator I found cause...corrosion on terminals for the alternator connection at the battery. They looked good from the outside, but when I moved the wires the lug almost fell off in my hand. Cut back wire, crimped on new lug...voltage jump;ed right up!


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## gmags (May 3, 2001)

*Re: battery light on 'till revved (spitpilot)*

thanks everybody~
i'll make sure i double check the alt. connection to the battery also!...i did clean the battery terminals on sunday, but no difference.. 
it's not really effecting the charging otherwise. sometimes in the morning though, i'll start the car without sitting in it. if i do that the light will stay on until i get in and goose the pedal.


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## 2000GTIGLX (Jul 11, 2000)

*Re: battery light on 'till revved (gmags)*

This is completely normal behavior as stated above. The light will stay on until revved up. That is the function of the blue wire that goes to the red led from the alternator (at least it is blue on early cars). Regardless, no need to worry everything s working just fine.
Brad


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## 84_GLI_coupe (Apr 3, 2001)

*Re: battery light on 'till revved (2000GTIGLX)*

100% normal! If, however, the light DOESN'T come on when you turn the key, the alternator plug might be disconnected from the alternator (as was the case with my Bunny a little while back).


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## 89turbrio (Aug 31, 2001)

*Re: battery light on 'till revved (gmags)*

Dude, This is exactly my problem. If you have a volt guage in your car, maybe this will also sound familiar... Energize the ignition but not to start it, the signal goes from 7 then a second later it will jump up to normal ie:12. I have to do this little ritual to have it start right up. Sometimes the volts jump up to like 14-15. Is this also a trouble sign?
I have a prob that might coincide with this- electrical systems dying off above 3K. Let the revs drop below this and everything comes back. Anybody think this is an alternator prob? 
I tell you, I'm going to check the alternator to battery connection like Spitpilot suggested. I do clean my terminals regularly, and just cleaned them to r/o bad battery connection for this problem.


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## luisgp (Oct 18, 2001)

*Re: battery light on 'till revved (89turbrio)*

This thing happens because the external coils of the alternator need to be energized in order to produce electricity. Sometimes idle speed is not enough to do this, so it won't charge until it's revved up a little. Once they are charged, everythig should be fine.
This is normal stuff. Perhaps, as they say, cleaning the connections would help it a little, but I doubt it. 
The difference between an alternator and a generator is the same as with a DC motor to an AC induction motor. The Generator is exactly the same as a DC, and has carbon contacts, with inner and outer coils. the inner coils are energized with the help of the carbon contacts. 
The alternator works like an AC induction motor and is contactless, so it needs less maintenance. It produces AC current which is then turned into DC with a diode bridge inside the alternator. The core has no electrical contact with the exterior and is energized by the magnetic field generated by the outer coils. That's why it needs to be excited to start working.
I hope this clarifies things a bit.
Luis


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## killa (Nov 26, 2000)

*Re: battery light on 'till revved (luisgp)*

this is normal, if the idle stabilizer valve is workin properly, you idle will go to 2000 when cold and you wont see the light, if you idle low, you'll have the light because the alternator needs to be "revved" to have the light go away.


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## B3VR6 (Jan 4, 2000)

*Re: battery light on 'till revved (killa)*

Almost 100% sure it's your voltage regulator. There are 3 diodes in the regulator.. when one or 2 of those go bad, you'll have this very issue. It happened all the time to the 85 Jetta I had back in high school until I replaced the regulator (mounted on the end of the alternator) for $13.


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## 89turbrio (Aug 31, 2001)

*Re: battery light on 'till revved (B3VR6)*

Word B3VR6. helped out my problem with low volts at night- 360w low beam light output (2x80w/100w 6" rounds + 2x100w driving) + my a/c on.
thanks


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## Frankulie (Jul 17, 2001)

*Re: battery light on 'till revved (gmags)*

There seems to be a 'problem' with
the alternator light on probably 75%
of older VW. Thing is ,the problem is
related to voltage in the curcuitry
( voltage regulator!?) and not an
indication of an actual problem with
the alternator or the charging circuit.
I'll say what others said '' If the light
doesn't turn off when you rev it, THEN
you have a problem !!








It's sorta like the temp gage that rises when
you turn the lights on, again, voltage regulator?!








But you say you changed the regulator.....mmmmm.


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## AdidasCU (Jul 24, 2001)

*Re: battery light on 'till revved (Frankulie)*

You think that's bad!!!! HA!!!!
My G/F's 2000 Protege batt. light goes off... Catch is...
*It goes off when under LOAD!!!!* WTF??? I can understand why it might go off at idle, but under load!!!!
Anyone have any guesses?
James


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## Vdubs (May 16, 2001)

*Re: battery light on 'till revved (AdidasCU)*

It might be common but it's not normal (normal suggests correct), the alt should have kicked in at idle. An alt needs to spin at 1500 rpms before it starts charging, as it's turning at twice the speed of the crank it would be turning 2400 before it starts to charge in your case. It's a typical sign of an old alternator, you will find if the car spends a lot of time at idle speed you will end up with a flat battery and it's max output is down.


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