battery light on. after body work. no charge to Battery?

[goffoz]

So I had a little body work done last week , required some welding of the sheet metal...dent pulling
This is on a 86 tintop with a GW Aux battery set up.
The guy doing it is a pro...i showed him the Aux bat....so hopefully He knows his stuff.
Anyhow. When I pick the van up the battery light is on at engine start up, and stays on, I was night driving, so by the time i got home it was very obvious that the alternator is not charging the batteries at all.
I cycled the ignition and can't hear the GW solenoid activate.(under the seat)
So obviously there is no power in the blue wire from the fuse panel
Won't be able to look at this till the weekend, anyone have any idea of the most likely damage done to this circuit? that would cause this?
The guy says He only disconnected the battery grounds..not his fault
...and yes I checked the engine belts all good. Alternator is new-ish
Thanks for and help on this

[MarkWard]

It is a simple circuit. If you remove the blue wire from the alternator, the light should go out. If it does, the wiring is correct and I would be suspect of the alternator itself.

You might try removing the regulator and looking at the brushes and the commutator section of the rotor where the brushes ride. If some welding was done, as long as the battery ground was removed, the alternator should not have been affected.

Another possibility is some bondo dust was drawn into the alternator and affecting how the brushes contact the rotor. When the alternator is turning, there is quite a bit of airflow through it to cool it.
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[Terry Kay]

A Simple Charging Test off of the battery or atlernator will tell you immediatly if the alternator is charging or not.

Check that out first.
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T.K.

[goffoz]

[goffoz]

[erdonline]

You still need to test the voltage at the alternator with the van running. You don't show increased voltage at the battery with the van running, but there's still the possibililty that the alternator is putting out its proper voltage, but not getting to the battery.

Ed
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'85 Vanagon Westfalia
'84 Vanagon 7-passenger
'98 Mexican air-cooled Beetle

[Terry Kay]

If the ignition was off while the welding was going on, it'd be pretty tough to just fry the alternator.

The spike would have probably wacked the ECU too.

Just to 100% verify;

Start the van, pull off the positive battery cable ..
If the engine dies, time for a new dynamo.
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T.K.

[goffoz]

[goffoz]

[Terry Kay]

None other than the engine dying if the alternator / regulator is dead.
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T.K.

[goffoz]

[crazyvwvanman]

That test does not by itself prove that the alternator is bad. It may be but you need more testing to know for sure. When the key is turned on power is put onto the blue wire that attaches to the alternator. This supplies it a small current to activate the magnetic field so charging can start once the alternator is turning. When the key is on measure the voltage at the blue wire where it attaches to the alternator. If the key-on power is not reaching the alternator over the blue wire then the alternator will have a much harder time getting going. That would not be the fault of the alternator itself.

Because the GW aux battery relay usually also attaches to the blue wire circuit it complicates some of the diagnosis with respect to the alternator warning light.

Mark

[Terry Kay]

Just to re-affirm.

You saw zero juice on your tester when you checked out the power supply to the battery, and when you ynaked the cable the engine stut down.

Trust me--you've done the end of the road test--the alternator is not putting out any juice--
The engine would have remained running if it was.
Just as would happen in any other normal vehicle.

Now--Like I mentioned.
If the alternator got wacked just by welding on the body, the guy doing the welding would have had to have the ground to the welder hooked up direct to the alternator, and have the ignition switch on.
I really doubt that this fried it--

You can file a complaint, but I think they are going to tell you the same thing--

Good Luck,
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T.K.

[goffoz]

[goffoz]

[Terry Kay]

With the engine running--you should see 14 volts--14.1, 14.2 no problem.
Your not getting enough juice.
That's why the engine quit when you yanked the cable to the battery.
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T.K.

[crazyvwvanman]

We know the alternator is not charging. But we don't know that it is because the alternator is broken. The blue wire circuit feeds key-on power to the alternator to initiate charging. Make sure this activation power is getting to the alternator. If it is, then blame the alternator.

Mark

[MarkWard]

You can use a 12 volt test light in place of the blue wire for exciting the alternator. Clip the test light to the positive side of the van's power. Probe the terminal where the blue wire attaches, the test light should light. Note: It will also light if you touch the case of the alternator.

With the test light illuminated touching the stud where the blue wire attaches, start the engine and rev the engine, the test light should go out. What is happening is the stud acts like a ground when the engine is off and the key is on. That illuminates the bulb in the dash. When the engine starts, charging voltage is fed out the stud where the blue wire attaches and cancels out the warning light. 12 volts on both sides of the bulb. The load of the warning light is what excites the alternator into charging.

A glowing Alternator light indicates a " difference" in voltage on the two legs of the warning lamp.

There is such a thing as coincidence. You may be experiencing coincidence. Mark is suggesting before replacing the alternator to ensure the wiring is correct. That makes sense to me.
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[Terry Kay]

The blue wire frying due to some welding on the back end of the Van is about as remote as the alternator frying--
But yea--take a look at it prior to yanking the alternator, just for the heck of it.
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T.K.

[goffoz]

So now I'm completely stumped
Took the OEM alternator in and had it tested at two(2) stores, Oriellys and Autozone,both confirmed that it failed...watched them do the test.
Purchased a remanufactured (and tested..I watched) unit from Oriellys
installed it.
WTF
battery light still ON
NO volts on the blue wire...at the Alt, or at the solenoid for the GW Aux battery.
No volts(12.8 battery voltage) at the start battery, no volts from the +termal at the Alt to Grnd

So this is a good tested Alt installed correctly, good belt (I can see it spinning)

This is a system that was working perfectly before the bodywork.
All fuses are good, all the wiring looks good...no burns no breaks.
...grounds are good...no sign of damage.
The Alt test confirmed the original was bad
...New Alt is confirmed good
Unfortunately after install of the new unit, I'm getting the same result in the car...no charge

Tracked the path in the bently(61) leads to a diode in the foil?visually looks fine...Bently suggests a grnd fault somewhere on the circuit. any ideas?
What am I missing here???