low charge voltage 12.8

[drlong]

So I have been searching and reading for a couple of hours with no luck finding what the info I'm looking for.
My battery is only getting 12.8 volts when running. I ran the voltage tests for the voltage regulator and all seem correct except the D+ voltage when running is 12.8v instead of 14. Am I correct in thinking this is pointing to the alternator ?
1972 bus.
_________________
If it's not broke it must not be a VW

[74 Thing]

At what rpm are you getting that voltage and are you checking with a multimeter at the battery terminals?

Could be your regulator, brushes or alternator or cables.

[Magion]

I have this exact problem too. I have 75ah alternator. What I see is initially I get 14V but within minute or two it drops down to 12.8 at terminals. If you tested regulator according to Ratwell site you noticed that his method is only good for an early version?

For now I gave up as electricity is not my strong side. My conclusion was that some of the diodes could be bad in the alternator.
_________________
1975 Westfalia in Brilliant Orange
1995 Westfalia in Caribbean Green

[telford dorr]

Easy to check.

1st, a schematic of the alternator/regulator connections:

To test:
- unplug the regulator.
- make up a 6" wire with a male blade terminal on each end.
- use this wire to jumper the red (D+) and green (Df) wires together at the regulator plug. [Note: the brown (D-) wire is grounded internally inside the alternator.]
- connect a voltmeter across the battery.
- start the engine. DO NOT REV!
- watch the voltmeter while slowly increasing engine speed. The voltmeter should rise up to 14.4 volts (it will go HIGHER - DON'T LET IT!)
- also check the voltage at the red (D+) alternator wire. It should be roughly the same as the battery voltage for any given engine speed.

If this test passes, the issue is the voltage regulator. If not, it's the alternator.

What this test does is run the alternator wide open, unregulated. Thus, the output voltage is unlimited, and controlled only by engine speed. BE CAREFUL - you can fry electronic stuff if this gets away from you!
_________________
'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)

[Magion]

Thank you for an easy to understand test. Going to test it today!
_________________
1975 Westfalia in Brilliant Orange
1995 Westfalia in Caribbean Green

[drlong]

Thank you. That is exactly the test I was looking for.
_________________
If it's not broke it must not be a VW

[drlong]

Telford. That was it. Bad voltage regulator. So much easier than replacing alternator.
Got one on it way. Cheep beru but now I can buy a good one if needed.
_________________
If it's not broke it must not be a VW

[WhirledTraveller]

From here you can order a cheap compatible voltage regulator that allows you to adjust the voltage set point, which can be useful.

https://www.240turbo.com/AdjustableVoltage.html
_________________
1977 Westy, Automatic. Big Valve heads, CS Cam.

[Magion]

Hi Telford, same here... I used your method and I got the same result. Bad voltage regulator. So I bought new one - the Hüco 130216 which was available to me. When I measure on the terminals now I get all the way up to almost 17V when I rev the engine. Me thinks the new voltage regulator is piece of crap just as others said on here. I will go hunt down NOS one. I really hope i did not do any damage as I did only let it quickly climb and shut the engine down. Now back to old regulator with same result again back to 12.8v
_________________
1975 Westfalia in Brilliant Orange
1995 Westfalia in Caribbean Green

[telford dorr]

I can't believe, in this day and age, why there are SO MANY PROBLEMS with something so simple as a voltage regulator. There's nothing magical or special about it. Here's a typical schematic:

Using a modern 3-terminal "programmable" reference chip (TL431), I could get rid of about half of the original parts. You could build this on a piece of prototype board in an afternoon from scratch.

Relative to something like a modern engine or body control module, a regulator is a big nothing. Should be trivial for almost anyone in the aftermarket electrical parts biz...

I guess analog design has become a lost art: if you can't buy the whole thing as a single chip, or do it digitally with software and a microcontroller, then it just can't be built anymore.

Sorry state of affairs, if you ask me...
_________________
'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)

[Magion]

But bottom line is, if I understood correctly, if the regulator functions correctly I should not be able to measure anything over 14/14.4V on battery terminals right?

Funny thing is CIP1 has picture of this Hüco regulator wit made in Germany on it. I thought myself ok what would be so hard on this especially if its made in Germany. Reality is - it says Hüco Germany on it
_________________
1975 Westfalia in Brilliant Orange
1995 Westfalia in Caribbean Green

[alman72]

[telford dorr]

[SGKent]

[alman72]

what would it cost you to build a few? I know NOS ones are 70 to 100plus. and if new ones suck, i dont see why some folks would not drop 80-100 on a reliable part. I dont need one, just putting it out there.
I THINK that the old mentality of these being cheap vehicle to work on has just about gone.

[telford dorr]

[Magion]

I really DO appreciate your input on this!

I just spoke to one of the RF technicians here at my work and he is saying that maybe if the VR shows initial charging of 14V followed by drop to 12.8V it maybe not bad. also apparently with dual batteries it is easier on the alternator.

My question is: with 70a alternator and one of the batteries sitting at lets say 70% of charge would be this normal behavior fo VR to only show 14V for 10 sec followed by drop to 12.8V?
_________________
1975 Westfalia in Brilliant Orange
1995 Westfalia in Caribbean Green

[telford dorr]

[telford dorr]

[Wildthings]