It has happened to most of us. Working on one thing and something else happens. I did a search for No alternator light in different forms and all I been getting for results are "my alternator light is on. Just the opposite. When I put the key in the ignition and turn it to the on position the alternator light is doesn't go on. I have about 13 volts in the battery. and everything seems to be ok. Anybody know what's going on?
Tom
[url=http:www.mediafire.com/convkey/7340/e29fqva0ooqus716g.jpg[/img]http:www.mediafire.com/convkey/7340/e29fqva0ooqus716g.jpg[/img[/url]
No alt light
Moderator: Fatmobile
No alt light
Last edited by Tac on Mon Nov 16, 2015 10:08 am, edited 1 time in total.
1991 Jetta 1.6 ME N/A.
Re: No alt light
There's a feedback wire that runs from the alt (at least on 86 vintage) that runs the alt light. This wire could have a short, a bad connection, or the LED light could be burned out. If you have a Bentley, there should be the wire that runs from the alt back to the dash for this light shown in the wiring diagram.
Everybody else lists their cars here - but not me.
I have too many to count
I have too many to count
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- Turbo Charger
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Re: No alt light
The blue wire on the alternator frequently gets broken inside the insulation, right near the alternator. Engine vibration is amplified out there away from the crank's center of rotation.
A good test is to meter the battery before starting the engine, and again after revving... the voltage should go up.
If the voltage does not go up, a jumper of +12V to the exciter terminal of the alternator should make it go up (engine running).
With the key off, there should be no voltage at the small terminal on the alternator. Key on, there should be ~11V until the alternator kicks on and then there should be the same voltage as the output of the alternator.
A good test is to meter the battery before starting the engine, and again after revving... the voltage should go up.
If the voltage does not go up, a jumper of +12V to the exciter terminal of the alternator should make it go up (engine running).
With the key off, there should be no voltage at the small terminal on the alternator. Key on, there should be ~11V until the alternator kicks on and then there should be the same voltage as the output of the alternator.
Have a nice day.
'91 Jetta ECOdiesel TD - clean & complete (less motor/tranny) for sale
'82 Westy Vanagon 1.9 N/A - 23.5mpg
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'91 Jetta ECOdiesel TD - clean & complete (less motor/tranny) for sale
'82 Westy Vanagon 1.9 N/A - 23.5mpg
'86 Jetta TD - 45-50mpg
'81 Dasher Wagon 1.6 N/A - 52mpg
'84 Wasserboxer - DOA, parts donor
'94 Passat wagon VR6
'03 Jetta TDI wagon 230K, 52.3mpg
'89 Jetta N/A - 51mpg
'82 Caddy 1.6 N/A - Sold
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- Cetane Booster
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Re: No alt light
Also check the 5 amp fuse labeled "radio". It powers the whole dash cluster. If it's blown the battery won't charge, but it might take a while to notice.
82 pickup 1.6 n/a
350,000 + miles lost to broken odo
11mm block, 12mm head
350,000 + miles lost to broken odo
11mm block, 12mm head
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- Global Moderator
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Re: No alt light
I think the regulator can cause this too.
Remove it clean the ground spots and reinstall.
Remove it clean the ground spots and reinstall.
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'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
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2003 TDI wagon
2000 TDI Jetta.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
Re: No alt light
Thanks that's a lot of good info. That's this week ends project, after I fix my heat situation.
Thanks again
Tom
Thanks again
Tom
1991 Jetta 1.6 ME N/A.
Re: No alt light
You guys were right. It was the exciter wire. The blade connector was broken. After I repaired it, It still wasn't on. After tracing the wire I seen it was broke at the plug near the battery. I just touched it a little bit and the red wire broke right off (age and heat I guess). Light is working the way it should. Got another problem with another dash light I'll post in a new tread.
Thanks again, pics below for any one having the same problem.
Tom
https://www.mediafire.com/folder/phq1sn ... aba/shared
Thanks again, pics below for any one having the same problem.
Tom
https://www.mediafire.com/folder/phq1sn ... aba/shared
1991 Jetta 1.6 ME N/A.