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telford dorr
Samba Member
Joined: March 11, 2009
Posts: 3632
Location: San Diego (Encinitas)
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 Posted: Wed Mar 01, 2017 4:40 pm Post subject: Re: alternator not charging, no idiot light |
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| Multi69s wrote: |
| When testing the regulator you show D- going through the regulator and back to common on the power supply. Is it supposed to ground through the body of the regulator? My regulator has no continuity between D- and the shell. |
Yes, but maybe not directly.
Regulators come in two forms:
- those that internally connect D- to ground (the regulator case) and regulate by switching Df to D+.
- those that internally connect Df to D+ and regulate by switching D- to ground.
The alternator doesn't really care which way it's done. It just makes debugging a little more difficult. You can tell which way yours works by measuring D- and Df with a voltmeter (assuming a working alternator/regulator and running engine):
In the first case, D- will measure around zero and Df will fluctuate as a function of engine speed.
In the second case, Df will measure around 13.8 - 14.4 volts and D- will fluctuate with engine speed.
| Quote: |
As for the alternator, the only way that I can get the dash light to illuminate is when I ground the blue wire. I checked the wiring and the signal from the blue wire is going to the D+ of the alternator.
This would lead me to believe that something in the alternator is not allowing the activation current to energies the alternator. Or am I way off base? |
You're close.
Disconnect the regulator and measure the resistance between the D- (brown) and Df (green) wires of the alternator harness. Should read a low value. If not, then the alternator has issues (bad rotor, bad brushes) or the harness is broken. If the reading is OK, then the regulator has issues. Make sure the regulator is well grounded when remounting it to the bus.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST) |
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Multi69s
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Joined: January 24, 2006
Posts: 5583
Location: Lefty, CA
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telford dorr
Samba Member
Joined: March 11, 2009
Posts: 3632
Location: San Diego (Encinitas)
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| Posted: Thu Mar 02, 2017 10:15 am Post subject: Re: alternator not charging, no idiot light |
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| Multi69s wrote: |
| I've been dreading it since I have a pinched nerve in my back right now. |
I know that feeling quite well. It sucks.
If you're anywhere near the San Diego area, PM Aeromech. I'm sure he can help you out.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST) |
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Multi69s
Samba Member
Joined: January 24, 2006
Posts: 5583
Location: Lefty, CA
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Multi69s
Samba Member
Joined: January 24, 2006
Posts: 5583
Location: Lefty, CA
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| Posted: Sun Mar 12, 2017 11:53 am Post subject: Re: alternator not charging, no idiot light |
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Just an update. I think I found my problem. It looks like it was a Murphy's lay cascading effect. Since I have the engine in a Squareback, I had to fab up a totally sealed fresh air shroud, that completely covers the front of the fan, and the alternator.
When I pulled off the cover, the belt was broken, but that didn't explain why the idiot light wouldn't come on. I also tested the alternator through the brushes, and there was no continuity. So I pulled the alternator apart and this is what I found.
One of the wires from the windings to the slip ring was broken. In fact the part of the wire that connected to the slip ring was no where to be found. I then noticed that the main cooling fan was missing a blade (it was there previously), and there was a big chunk missing in the belt. So I am thinking that the blade came off, and traveled through the system causing the damage.
I don't believe that it was electrical (wire melting) because I can measure from the broken wire to the other slip ring and I have about 5 ohms, and when I check for shorts from the wire to the rotor body there is none.
Thanks for everyone's help.
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
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AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight= |
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