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NateBug1970 Samba Member
Joined: September 21, 2021 Posts: 4 Location: California
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Posted: Wed Sep 22, 2021 8:35 pm Post subject: Generator light comes on when ignition is turned off |
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Hello everyone! So I recently bought my 12 yr old daughter a 1970 beetle to fix up and have ready by the time she's able to drive. I had to replace the battery because my wife left the lights on. The new battery had the - & + on the opposite sides from the old battery and so without checking I began to hook up the new battery backwards and along came some sparks. This blew the stereo fuse and caused my generator light in the speedometer to come on and stay on after the ignition is turned off. The generator and oil lights both still come on and go off as normal when the engine turns on. Does the light staying on mean that the generator was blown? Thanks in advance for any answers.
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VW_Jimbo Samba Member
Joined: May 22, 2016 Posts: 9966 Location: Huntington Beach, CA
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Posted: Wed Sep 22, 2021 10:13 pm Post subject: Re: Generator light comes on when ignition is turned off |
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So…..
That is an Alternator. Not a generator. Newbie mistake.
The light remaining on means you reversed polarity at the regulator and killed the diode(s) within.
If you know how to rebuild an Alternator then you got this. If not, purchase a new or rebuilt unit and swap it out.
That picture makes it look like the thick red wire is coming out of the Collins hole on the fan cover! Really odd looking!
Is there a bluish colored wire connected to the alternator? I am unable to tell from the picture.
Good luck!
Heads up! You might want to remove that engine compartment photo ASAP, before the engine compartment police come for you! _________________ Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
TDCTDI wrote: |
Basically, a whole bunch of fuckery to achieve a look. |
67rustavenger wrote: |
GFY's Xevin and VW_Jimbo! |
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NateBug1970 Samba Member
Joined: September 21, 2021 Posts: 4 Location: California
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Posted: Thu Sep 23, 2021 8:13 am Post subject: Re: Generator light comes on when ignition is turned off |
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Thanks for the reply. These are the three wires connected to the alternator. So I guess there's no external voltage regulator on these which explains why I couldn't locate one.
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ashman40 Samba Member
Joined: February 16, 2007 Posts: 15985 Location: North Florida, USA
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Posted: Thu Sep 23, 2021 2:37 pm Post subject: Re: Generator light comes on when ignition is turned off |
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Yeah, sounds like you blew the internal regulator in your alternator. The best option may be to go to your FLAPS and source a rebuilt alternator ('75-later Beetle) with a Lifetime warranty. Autozone is pretty good both in quality and supporting the warranty. Have the FLAPS test the alternator before you walk out of the store. Take your alternator pulley parts to assemble on your new alternator. You don't want to spend hours installing a dud only to have to remove it and reinstall a 2nd replacement alternator.
There should only be 2 wires connected to the alternator. The larger B+ wire connects to the threaded stud and smaller D+ wire to the D+ push on terminal.
I see a 3rd wire there which looks like it connects to the case as a ground wire. The earlier generator wiring had 3-wires, one of which was a brown ground wire. This wire is not used when wiring an internally regulated alternator. I recommend you disconnect it. _________________ AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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Starbucket Samba Member
Joined: April 30, 2007 Posts: 4025 Location: WA
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Posted: Thu Sep 23, 2021 2:48 pm Post subject: Re: Generator light comes on when ignition is turned off |
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Remove the 3 screws that hold the brush (where the blue wire connects) and see if you just melted the brush wire. |
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ashman40 Samba Member
Joined: February 16, 2007 Posts: 15985 Location: North Florida, USA
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Posted: Fri Sep 24, 2021 7:41 am Post subject: Re: Generator light comes on when ignition is turned off |
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Starbucket wrote: |
Remove the 3 screws that hold the brush (where the blue wire connects) and see if you just melted the brush wire. |
If the GEN lamp is remaining ON after the key is turned to OFF, it is not the brushes.
Correction to my above where I said the internal regulator has been blown... it more likely the diode-trio (rectifier bridge) that has failed. These diodes allow the alternating-current (AC) generated by the spinning alternator to be converted to direct-current (DC) for use in the 12v DC system of the car. When one or more of these diodes fail they allow current from the B+ wire (which is connected to the battery +) to pass thru the alternator and come out the D+ terminal. This powers the GEN lamp when the ignition is turned OFF.
The diodes are not something you can removed while the alternator is on the car. You need to gut the alternator internals to reach the diodes. _________________ AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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NateBug1970 Samba Member
Joined: September 21, 2021 Posts: 4 Location: California
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Posted: Fri Sep 24, 2021 11:33 am Post subject: Re: Generator light comes on when ignition is turned off |
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Ok so you are saying that I should disconnect and leave disconnected the extra write that is not connected to the D+ and B+ when I install the new alternator. Also, I am thinking of transitioning from the my current 1600 to a 1776 for more power and daily driving. Is there a certain type of alternator that I should get anticipating the engine change or will it not matter? Thanks again for the replies. |
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ashman40 Samba Member
Joined: February 16, 2007 Posts: 15985 Location: North Florida, USA
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Posted: Fri Sep 24, 2021 11:51 am Post subject: Re: Generator light comes on when ignition is turned off |
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NateBug1970 wrote: |
Ok so you are saying that I should disconnect and leave disconnected the extra write that is not connected to the D+ and B+ when I install the new alternator. |
Yes, that 3rd wire is not need and could create an alternate ground path.
Also, until you replace your alternator you should disconnect the negative battery cable from the battery so the GEN lamp won't drain the battery.
NateBug1970 wrote: |
Also, I am thinking of transitioning from the my current 1600 to a 1776 for more power and daily driving. Is there a certain type of alternator that I should get anticipating the engine change or will it not matter? Thanks again for the replies. |
The engine doesn't care which alternator you use as long as it provides power to run the car's electrical system.
Now, if you plan to run a large stereo or something that will draw more watts from the electrical system, you may consider upgrading your alternator.
The stock VW alternator is a 50/55A unit. This was a big upgrade from the 35A generators. Rebuilt 50/55A alternators you can pick up at almost any FLAPS. That should be fine for 80% of the cars out there.
But there are aftermarket alternators that output 75A/80A/90A/100A. You will pay more for them but if you need more power now is the time to upgrade since you have to remove the alternator anyway. For those higher output alternators you may also need to upgrade the gauge of the B+ wire to something that can carry more current w/ less loss. You migh also consider routing the B+ wire from the alternator down to the battery cable on the starter solenoid. This is a shorter run and leaves the wire exposed to more air flow to keep it cooler than in a harness running thru the C-pillar. _________________ AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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Starbucket Samba Member
Joined: April 30, 2007 Posts: 4025 Location: WA
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Posted: Fri Sep 24, 2021 1:13 pm Post subject: Re: Generator light comes on when ignition is turned off |
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ashman40 wrote: |
Starbucket wrote: |
Remove the 3 screws that hold the brush (where the blue wire connects) and see if you just melted the brush wire.
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If the GEN lamp is remaining ON after the key is turned to OFF, it is not the brushes.
Correction to my above where I said the internal regulator has been blown... it more likely the diode-trio (rectifier bridge) that has failed. These diodes allow the alternating-current (AC) generated by the spinning alternator to be converted to direct-current (DC) for use in the 12v DC system of the car. When one or more of these diodes fail they allow current from the B+ wire (which is connected to the battery +) to pass thru the alternator and come out the D+ terminal. This powers the GEN lamp when the ignition is turned OFF.
The diodes are not something you can removed while the alternator is on the car. You need to gut the alternator internals to reach the diodes. |
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If the GEN lamp is remaining ON after the key is turned to OFF, it is not the brushes.
That may be true, but by you talking him out of looking later on when his new alt. quits charging he will just buy a new alt. instead of looking to see if it's just a simple cheap fix and have to go through the hassle of removing the alt.. |
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NateBug1970 Samba Member
Joined: September 21, 2021 Posts: 4 Location: California
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Posted: Fri Sep 24, 2021 7:18 pm Post subject: Re: Generator light comes on when ignition is turned off |
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Awesome! Thanks guys |
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ashman40 Samba Member
Joined: February 16, 2007 Posts: 15985 Location: North Florida, USA
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Posted: Sat Sep 25, 2021 2:25 pm Post subject: Re: Generator light comes on when ignition is turned off |
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Starbucket wrote: |
ashman40 wrote: |
If the GEN lamp is remaining ON after the key is turned to OFF, it is not the brushes. |
That may be true, but by you talking him out of looking later on when his new alt. quits charging he will just buy a new alt. instead of looking to see if it's just a simple cheap fix and have to go through the hassle of removing the alt.. |
Good point. If there was any type of charging issue, checking the easy to access brushes should be something to do before pulling the alternator which is no small amount of work. _________________ AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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