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Author Topic: Have to rev eng to make Alt light go out  (Read 5491 times)

December 09, 2007, 08:22:12 pm

AudiVWguy

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Have to rev eng to make Alt light go out
« on: December 09, 2007, 08:22:12 pm »
MK1 Pickup, no ac. I got tired of having to rev the engine to almost 2000 rpm to get the alternator light to go out. The Bently book points towards the diodes. So I take it in to have it rebuilt. They check everything, nothing wrong with the diodes. Replace voltage regulator and bearings, I'm on my way. Still is doing the same thing! They wanted to know the voltage of the trigger wire. Key on  12v  at the wire/plug. plug it in to the alternator it drops to 1.8v. They say this it's ok and is enough to trigger the alternator.  So what now? Anybody else have a similar situation?
Thanks
-JB
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Reply #1December 09, 2007, 08:47:36 pm

burn_your_money

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Have to rev eng to make Alt light go out
« Reply #1 on: December 09, 2007, 08:47:36 pm »
Your blue exciter wire is probably making a bad connection somewhere.
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Tyler
Reply #2December 09, 2007, 08:48:12 pm

jtanguay

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Have to rev eng to make Alt light go out
« Reply #2 on: December 09, 2007, 08:48:12 pm »
every vw i've ever owned neede a 'blip' on the throttle/pedal to turn on the alternator.

this one time i started my car to let it warm up i forgot to blip the throttle.. go outside and it was dead.  battery ran outa juice!!  :lol:

could be something to do with the exciter wire?  is the belt tight enough?  its probably some loose/corroded wire connection.  i hate small electrical problems like that.
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Reply #3December 09, 2007, 08:48:51 pm

Vincent Waldon

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Have to rev eng to make Alt light go out
« Reply #3 on: December 09, 2007, 08:48:51 pm »
Most VWs with LED warning lights have this "feature"... it's even mentioned specifically in the owners manual of my early MK2 as a "not to worry".

The alternator needs a certain amount of energy to "self-excite"... once it gets past that threshold it carries on... but a blip of the throttle is required to get it started.

One of my VWs does it at about 1200 rpm, the other at 1400.

I would certainly check wiring, belt tension, connection at the cluster, etc., but unless it just started to do it you may have an alternator that is just a little more grumpy in the morning.
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Reply #4December 09, 2007, 08:50:47 pm

burn_your_money

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Have to rev eng to make Alt light go out
« Reply #4 on: December 09, 2007, 08:50:47 pm »
My old mk2 did not require this blip. It would kick in itself after about 5 seconds of idling. It did idle around 1000 though
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Tyler
Reply #5December 09, 2007, 10:59:35 pm

BejamminR

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Have to rev eng to make Alt light go out
« Reply #5 on: December 09, 2007, 10:59:35 pm »
My old Mk2 needed this "blip". My current Mk3 does not. (shrugs) I still do due to force of habit. What can you do?  :)
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Reply #6December 10, 2007, 07:47:28 am

FineFrank

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« Reply #6 on: December 10, 2007, 07:47:28 am »
I fixed mine by taking out the instrument cluster, removing the LED bulb for the alt. light, cleaning the wires, and reinstalling it. It's connected to the "blue" wire, and any extra resistance will cause the led to stay on until you rev the hell out of it.
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Reply #7January 03, 2008, 10:10:57 pm

Diesel Fumes

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Have to rev eng to make Alt light go out
« Reply #7 on: January 03, 2008, 10:10:57 pm »
Mine needs a blip to 3k RPM to kick in.  I think its about time I change it out with this Canadian Tire rebuild one :(
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Reply #8January 04, 2008, 02:59:01 am

Ziptar

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Have to rev eng to make Alt light go out
« Reply #8 on: January 04, 2008, 02:59:01 am »
My MKII also needs a blip to 1100 or so to get the Idiot Light to go out and get the tach to start registering.

My MkIV does not  :P
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Reply #9January 04, 2008, 04:45:36 am

somolovitch3

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Have to rev eng to make Alt light go out
« Reply #9 on: January 04, 2008, 04:45:36 am »
I am of the 50/50 group as well.  

Half of the VW's I have owned needed a "blip (2K RPM)" and half have not. Changing Alt does not seem to make a difference.

If you have the time and wire, (for grins :twisted: ) try running a wire from the Alt W connecter (?) to the correct terminal on the back of the dash, remembering to leave the othe wires attached. If it makes a difference, then check and clean EVERY wire and connection between the Alt and the dash. Like I said, if you have the time............ :roll:

Lots of posts on this subject lately........hummmmmmmmmmmm
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Reply #10January 04, 2008, 11:39:15 am

Zulfiqar

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Have to rev eng to make Alt light go out
« Reply #10 on: January 04, 2008, 11:39:15 am »
the original blue wire in the alternator harness is hairlike and gets dodgy from the connector going in the harness near the battery.

Try taking a new wire to it direct, worked for me (well I didnt have the alt harness in the first place)
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