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Multi69s
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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=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight= |
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Multi69s
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Joined: January 24, 2006
Posts: 5583
Location: Lefty, CA
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telford dorr
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Joined: March 11, 2009
Posts: 3631
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
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Joined: January 24, 2006
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Location: Lefty, CA
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telford dorr
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Joined: March 11, 2009
Posts: 3631
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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kooper271
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Joined: March 22, 2016
Posts: 337
Location: Ohio
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| Posted: Wed Mar 01, 2017 12:36 pm Post subject: Re: alternator not charging, no idiot light |
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| Multi69s wrote: |
Telford, a couple of questions.
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.
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Yes, the regulator body should be grounded. Telford mentions that in page 1 of this thread:
http://www.thesamba.com/vw/forum/viewtopic.php?t=673255 |
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TomWesty
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Joined: November 23, 2007
Posts: 3565
Location: Wyoming,USA
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| Posted: Wed Mar 01, 2017 12:34 pm Post subject: Re: alternator not charging, no idiot light |
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| Abscate wrote: |
You just need the ubiquitous step-up rheostat.
You can also take the extra voltage and charge your battery with it.
 |
Commonly referred to as the Transfrheostormer.
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Multi69s
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Joined: January 24, 2006
Posts: 5583
Location: Lefty, CA
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| Posted: Wed Mar 01, 2017 12:21 pm Post subject: Re: alternator not charging, no idiot light |
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| telford dorr wrote: |
You can quick-check the alternator for functionality with a quick rewire using some jumper wires. This is NOT a definitive test of the alternator, but will tell you if the regulator is the cause of the problem. Basically, we're going to remove the regulator from the circuit and run the alternator "wide open", varying the alternator output by varying engine speed. If your battery is good, this is safe for a short period of time. Note: I generally don't recommend doing this if you have FI, as FI can't take a joke.
Here's the stock alternator wiring:
What we're going to do is unplug the regulator and, using some jumper wires with blade terminals on their ends, connect the regulator wires as follows:
- D- wire to ground
- Df wire to D+
This will apply maximum rotor current to the alternator.
Connect a good voltmeter across the battery and start the engine. Watch the voltmeter carefully. Increase engine speed slowly. The battery voltage should increase. DO NOT allow it to rise to more than 14.4 volts, or 2500 rev/min max. If you can get the 14.4 volts, then the regulator is probably toast.
Note: for this test to work, the dash idiot light must illuminate when you first turn on the key, as it supplies the initial alternator activation current.
---
If you have access to a variable voltage power supply (or a "stupid' battery charger and a Variac), the regulator may be easily checked. Here's the test setup:
As you increase the power supply voltage, the test light will illuminate. As the voltage gets past somewhere around 13.8 to 14.4 volts, the light will suddenly go out. Decreasing the voltage will cause it to suddenly come back on. If it does this, the regulator is working. Note: if the regulator is a mechanical unit, don't let it run very long at the 'test light out" point, as it doesn't like it (the resistor on the bottom of the regulator will get quite hot). Ironically, the solid state regulators don't care. |
Telford, a couple of questions.
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.
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?
_________________
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=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight= |
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Abscate
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Joined: October 05, 2014
Posts: 24477
Location: NYC/Upstate/ROW
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| Posted: Fri Feb 24, 2017 2:00 pm Post subject: Re: alternator not charging, no idiot light |
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| telford dorr wrote: |
In this case, no.
- it would have to be one hell of a big rheostat. [You can do it easily with a small pot and a couple of transistors.]
- in this case, you need greater than battery voltage for the test.
Sorry. Good idea, but this time, no cigar... |
You just need the ubiquitous step-up rheostat.
You can also take the extra voltage and charge your battery with it.
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telford dorr
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Joined: March 11, 2009
Posts: 3631
Location: San Diego (Encinitas)
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| Posted: Fri Feb 24, 2017 11:44 am Post subject: Re: alternator not charging, no idiot light |
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In this case, no.
- it would have to be one hell of a big rheostat. [You can do it easily with a small pot and a couple of transistors.]
- in this case, you need greater than battery voltage for the test.
Sorry. Good idea, but this time, no cigar...
_________________
'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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lil-jinx
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Multi69s
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Joined: January 24, 2006
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telford dorr
Samba Member
Joined: March 11, 2009
Posts: 3631
Location: San Diego (Encinitas)
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| Posted: Sat Feb 18, 2017 9:22 am Post subject: Re: alternator not charging, no idiot light |
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You can quick-check the alternator for functionality with a quick rewire using some jumper wires. This is NOT a definitive test of the alternator, but will tell you if the regulator is the cause of the problem. Basically, we're going to remove the regulator from the circuit and run the alternator "wide open", varying the alternator output by varying engine speed. If your battery is good, this is safe for a short period of time. Note: I generally don't recommend doing this if you have FI, as FI can't take a joke.
Here's the stock alternator wiring:
What we're going to do is unplug the regulator and, using some jumper wires with blade terminals on their ends, connect the regulator wires as follows:
- D- wire to ground
- Df wire to D+
This will apply maximum rotor current to the alternator.
Connect a good voltmeter across the battery and start the engine. Watch the voltmeter carefully. Increase engine speed slowly. The battery voltage should increase. DO NOT allow it to rise to more than 14.4 volts, or 2500 rev/min max. If you can get the 14.4 volts, then the regulator is probably toast.
Note: for this test to work, the dash idiot light must illuminate when you first turn on the key, as it supplies the initial alternator activation current.
---
If you have access to a variable voltage power supply (or a "stupid' battery charger and a Variac), the regulator may be easily checked. Here's the test setup:
As you increase the power supply voltage, the test light will illuminate. As the voltage gets past somewhere around 13.8 to 14.4 volts, the light will suddenly go out. Decreasing the voltage will cause it to suddenly come back on. If it does this, the regulator is working. Note: if the regulator is a mechanical unit, don't let it run very long at the 'test light out" point, as it doesn't like it (the resistor on the bottom of the regulator will get quite hot). Ironically, the solid state regulators don't care.
_________________
'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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dawie
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Joined: July 27, 2008
Posts: 222
Location: Cape Town, South Africa
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| Posted: Fri Feb 17, 2017 11:41 pm Post subject: Re: alternator not charging, no idiot light |
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| Check the slipring brushes as well. Test by measuring resistance between DF wire from alternator and earth. |
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busdaddy
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Joined: February 12, 2004
Posts: 53222
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Fri Feb 17, 2017 9:19 pm Post subject: Re: alternator not charging, no idiot light |
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Sadly there's not many tests you can do on a regulator without a full bench simulator, some old school electric shops may still have such a rig gathering dust back in the corner. There are tests for the alternator so you can rule it out and blame something else, aside from the wiring and the regulator there's not much else to blame once that's done.
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Multi69s
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Joined: January 24, 2006
Posts: 5583
Location: Lefty, CA
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| Posted: Fri Feb 17, 2017 8:46 pm Post subject: Re: alternator not charging, no idiot light |
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It's kind of ironic, but there doesn't seem to be a good procedure anywhere for trouble shooting the regulator / Alternator. I've searched here, and my bus Bentley came in. The Bentley goes in depth on a generator, but it seems like the alternator was an after thought. I remembered that I had a Clymer 411/412 book. It does a great job on showing how to disassemble and test individual parts on the alternator, but nothing on determining whether the problem is the reg or alt in the first place. I refuse to spend $$$ chasing a problem. I am looking for any kind of procedure that will tell me which part of the charging system is causing the problem.
_________________
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=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight= |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 13631
Location: West Coast, USA
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| Posted: Fri Feb 17, 2017 5:29 pm Post subject: Re: alternator not charging, no idiot light |
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| sjbartnik wrote: |
| Spike0180 wrote: |
This must have changed from 1970 then. My bus just got its generator light working (previously not even wired) and ive driven a few hundred miles without it. |
Ah grasshopper, but generators are not alternators!  |
Check his signature: 1700 T4 in a '70 body. So it would be a gen light with an alternator. 
Robbie
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busdaddy
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Joined: February 12, 2004
Posts: 53222
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Thu Feb 16, 2017 6:51 pm Post subject: Re: alternator not charging, no idiot light |
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Have a look through these: http://www.thesamba.com/vw/forum/search.php?search..._chars=200
I always start with a good close look at the connectors and wires, it's not uncommon for a wire to break inside the insulation yet still look fine outside, sometimes they also push back out of the plug when connecting. After the visual use an OHM meter to confirm each wire is doing it's thing, even while pulling and wiggling the plug at each end.
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Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Multi69s
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bsairhead
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Joined: October 08, 2008
Posts: 4570
Location: viroqua wi.
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| Posted: Thu Feb 16, 2017 5:22 pm Post subject: Re: alternator not charging, no idiot light |
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| You can drive a long time on battery only. But as far as the gen/alt light all is same. |
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