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azbob Samba Member
Joined: April 04, 2010 Posts: 714 Location: Phoenix, AZ
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Posted: Sat Oct 19, 2013 7:57 am Post subject: Dim running dummy light? |
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Ok, I'm asking for a sanity check here. First time I ran the new build in the evening was last night. I noticed that when running the dummy light was still lit but barely. The bus has a freshly installed harness and all is working well. The switch is new.
When the key is set to the on position the light is bright - working as intended. When running the dummy light stays on but goes very dim.
Now my understanding is the oil pressure switch is either on or off. So this makes me wonder why the light would go to dim. Any ideas? Maybe a ground somewhere, even though that doesn't seem right...
I'll more than likely hook up an oil pressure gauge later today. I figured I'd post since this seems like it could be something normal or something completely serious.
Thanks! _________________ Bus Builder |
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BarryL Samba Member
Joined: November 01, 2004 Posts: 14255 Location: Casa de Oro, California
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Posted: Sat Oct 19, 2013 8:15 am Post subject: |
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Are you sure it's the oil one? If so, go ground it right to the case and see if it's still dim or off completly. That horseshoe contact under the speedo that feeds the oil and gen light power is kinda tricky. |
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azbob Samba Member
Joined: April 04, 2010 Posts: 714 Location: Phoenix, AZ
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Posted: Sat Oct 19, 2013 8:23 am Post subject: |
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@BarryL ah crap... Yeah, you're right, it's the gen/alt light... I need to wake up a bit more before posting!
That said, looks like I need a new bulb and/or housing for the dummy light.
I'm just going to go over here and drink my coffee... _________________ Bus Builder |
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Eric&Barb Samba Member
Joined: September 19, 2004 Posts: 24732 Location: Olympia Wash Rinse & Repeat
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Posted: Sat Oct 19, 2013 8:29 am Post subject: |
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Then you probably have a loose or dirty connection in the wiring.
Have you soldered up the internal connections of the fuse box and headlight switch? _________________ In Stereo, Where Available! |
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olliehank47 Samba Member
Joined: May 04, 2011 Posts: 1198
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Posted: Sat Oct 19, 2013 9:42 am Post subject: |
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Now that you have established it's the generator light, you have a different trouble shooting procedure.
The gen light comes on with the ignition switch because voltage is provided from the ignition switch, and the wire to the voltage regulator provides the ground. When the engine starts and the generator spins, the ground becomes energized and the light goes out. If the light remains on or dim, then either the connections are bad and you are not getting full voltage to the bulb, or the voltage regulator/generator is not providing full voltage. In either case, you should test the voltage at the bulb connection to see if you are receiving the full power from the generator. |
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azbob Samba Member
Joined: April 04, 2010 Posts: 714 Location: Phoenix, AZ
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Posted: Sat Oct 19, 2013 12:55 pm Post subject: |
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I have not soldered up anything at the fuse box.
I'll check the voltage at the light. The alternator is new, never used before. I'll double check the grounds. When doing the wiring harness, I did not replace the ground strap.
Thanks! _________________ Bus Builder |
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Eric&Barb Samba Member
Joined: September 19, 2004 Posts: 24732 Location: Olympia Wash Rinse & Repeat
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telford dorr Samba Member
Joined: March 11, 2009 Posts: 3551 Location: San Diego (Encinitas)
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Posted: Sat Oct 19, 2013 1:45 pm Post subject: |
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Here's a schematic showing the areas involved with the GEN idiot light:
Ignoring the battery for a moment, you can see that the GEN light is basically connected between regulator terminals 61 and B+. When all is working properly, these terminals are both at around 6.9 volts. Because the GEN bulb has 6.9 volts on both of its terminals, it has no voltage across it, and thus doesn't illuminate. If the generator were to fail, then regulator terminal 61's voltage goes to zero (roughly). Now there's 6 volts across the bulb (provided by the battery, and grounding through regulator terminal 61), and the bulb illuminates.
That's how it's supposed to work.
But look at the path the two voltages take. The path from the regulator terminal 61 goes directly to the bulb. The path from regulator terminal B+ takes a tortured route to the starter, then to the fuse block, then to the light switch, then through the ignition switch, then to bulb. If there's a flaky connection at one or more of these waypoints, then there will be a voltage drop. By the time the voltage gets to the GEN bulb, it has dropped enough to cause the bulb to glow slightly (even though the generator is working correctly).
To fix this problem, check, disassemble, clean, reassemble, and tighten all of the connections along the red and red/black wires. Once this is done, all should be right with the world...
If you have difficulties, use your voltmeter to measure the voltage at every connection along the red wire path. You should to be easily able to tell where thing start going wrong. Keep in mind that there's likely multiple points of failure, so check them all. Note that the voltage has to go through the ignition switch. If it's starting to fail, it will drop voltage, and the GEN bulb will glow. _________________ '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)
Last edited by telford dorr on Sun Oct 20, 2013 12:39 pm; edited 2 times in total |
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fresno james Samba Member
Joined: December 12, 2009 Posts: 559 Location: Kingman AZ
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Posted: Sat Oct 19, 2013 2:24 pm Post subject: |
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^^ NICE Telford Dorr !!!
^^^ Good link , and info. on this !!!
Very true / good point about all the load traveling through the switch causing grief .... Think this is gonna be my next rainy day project ... LOL _________________ JP Kustoms
contact info. [email protected]
Kingman AZ |
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azbob Samba Member
Joined: April 04, 2010 Posts: 714 Location: Phoenix, AZ
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Posted: Sat Oct 19, 2013 6:41 pm Post subject: |
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@Eric&Barb I'll have to go through that link when I get back to it later this week. I had never heard of anyone going through the fuse box till now. Thanks!
@telford dorr Awesome info! I'll go through with a voltage meter in the am and track it down as well as cleaning all the points of contact. That is one thing I don't think I did at the starter when I replaced the rest of the harness. Hopefully it is not the ignition starting to fail either! I just had all the doors keyed to it! Ha! Would be my luck though! Thanks for the write up! _________________ Bus Builder |
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BarryL Samba Member
Joined: November 01, 2004 Posts: 14255 Location: Casa de Oro, California
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Posted: Sat Oct 19, 2013 6:54 pm Post subject: |
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azbob wrote: |
The alternator is new, never used before. |
When using an alternator you don't use that diagram. The idiot bulb is on the exciter (little terminal) circuit and must be good and in place. To test that circuit turn the key on and go ground the exciter wire. It should be bright then go out when the alternator kicks in. |
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telford dorr Samba Member
Joined: March 11, 2009 Posts: 3551 Location: San Diego (Encinitas)
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Posted: Sun Oct 20, 2013 12:48 pm Post subject: |
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Actually, the diagram works fine for an alternator conversion. Note the original drawing shows the generator and regulator as one unit, with two wires going to it. Well, the alternator conversion (with internal regulator) is wired up exactly the same: same two wires going to it.
Now the battery symbol is wrong, as you're now running 12 volts instead of 6. And you need to double all of the diagnostic voltage reading values in the original post. _________________ '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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BarryL Samba Member
Joined: November 01, 2004 Posts: 14255 Location: Casa de Oro, California
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Posted: Sun Oct 20, 2013 2:15 pm Post subject: |
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telford dorr wrote: |
Actually, the diagram works fine for an alternator conversion. |
Ah so right. On my dialup I didn't see that and assumed it was the regulator on the support pic. Plus I don't know how he skirted the og regulator. |
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telford dorr Samba Member
Joined: March 11, 2009 Posts: 3551 Location: San Diego (Encinitas)
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Posted: Sun Oct 20, 2013 2:27 pm Post subject: |
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IIRC, on 6 volt buses, the regulator was mounted directly on the generator. When you pull it to replace it with an alternator, the regulator goes with it. Nice clean swap (unlike Bay Window buses, where the regulator is remotely mounted, and has to be wired around for an alternator swap). _________________ '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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