low alternator output?

[calo1956]

I have noticed that my volts drops low (12v) when i run the headlights. During the day with no load there near 14v. Back story, i added the headlight relay from Bus Depot, ran that alone for a year or so, then back in July decided to add the H4 lights as part of the kit, the bulbs are 90/100 watt, and no, not dot approved here in the US! So thrilled with having bright lights for the first time, till i noticed the volts went down to low 12's and in the 11's at idle with the headlights on. So figuring they were to much for the alt to handle, I switched to LED's, only drawing 30 watts and very bright. Right away i saw the volts back up to mid 13's while driving with them on. But recently i have noticed that the volts are back down more like mid 12's with the lights on, and drop to low 12's at idle. So is my alt failing?, or could there be some other issue?
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Enjoy the ride....
72 bug
80 westfalia

[zuhandenheit]

Well, of course something isn't right. It seems, though, that low voltage output is a common problem.

My diesel (AAZ) engine has always had a lower output than I'd like to see -- something I've been more concerned with after adding a second battery and swapping my main battery with a big AGM. I have a new alternator (incidentally, not a diesel alt, but one for a WBX) and the voltage is the same as with the original. I bought an adjustable voltage regulator and now have more consistent and after, adjustment, higher Vs.

In a recent discussion, a number of forum members discussed the likelihood that we're chronically undercharging out batteries. Because even good alternators don't seem to have very good output.

Grabbing an adjustable regulator is something you might try -- they're nice to have anyway, and it's possible the regulator on your alternator is the problem.

You should also test the battery and make sure the alt belt is not slipping.

[zuhandenheit]

https://vwparts.aircooled.net/Adjustable-Voltage-R...ulator.htm

[Team WorldTour]

Funny. I have an AAZ as well, and a brand new (120A) alternator. It's putting out 13.5 at the battery, just 8 inches away!
I've considered new cables, but I'm not sure how effective that would be....
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1990 Feldjäger Syncro AAZ
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When All Else Fails: Lather, Rinse, Repeat!

[calo1956]

Thanks zuhandenheit , i guess I'm not the only one with this issue, Thanks for the link AirCooled.net , its worth a try, there a little high for shipping $16 for a part smaller than a deck of cards! but thats neither here or there.Thanks again.
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Enjoy the ride....
72 bug
80 westfalia

[DanHoug]

i don't mean this snarkily but you have a 38 year old vehicle. of COURSE something is failing but it may not be the alternator. at this age, you need to do a complete charging system check. it'll take 15 minutes and pinpoint problem areas. there's lots of good posts on doing this but it boils down to looking for voltage drops between the alt and the battery when under load, the battery and accessories, and yes charging voltage.

in all likelihood you have a combination of factors going on... voltage drops due to corroded connections or cable, a weak battery, and possibly low alt output that may just be a regulator, the variable ones are nice. but at 38 years old, take the time to walk thru the whole system. 15 minutes.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[calo1956]

Thanks Dan
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Enjoy the ride....
72 bug
80 westfalia

[zuhandenheit]

[E1]

If you haven't, you need to test the battery in the second or two of cranking before it fires up.

If it drops below 10, it's most likely the battery. A good battery won't get anywhere close to 10 when cranking, the alternator can be totally fine but if the battery isn't taking the charge you stand a good chance of also destroying the alternator.

Another option is knowing the CCA (cold cranking amps) of the battery, and then with a load tester. Any parts store will do this, typically for free.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[crazyvwvanman]

It is a big mistake to judge the alternator by the voltage at the battery.
You need to measure at the alternator!
Measure unloaded and then with things turned on. It should stay nearly the same.
Next measure at the battery, first unloaded, then loaded. If too much lower than the voltages you got at the alternator then you may need to figure out why.

Ohms law rules this kingdom. Measuring only at the battery displays ignorance of the law.

Mark

[E1]

Good point Mark, I presumed the OP was testing the alternator on the case.

OP, are you? There's a ton of places the charge could be dropping between alternator and battery. We never see more than maybe 0.05 to 0.1 volt loss if testing on the alternator, and then again on the battery itself.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[Zeitgeist 13]

I had a voltage output issue with the alternator on my old WBX, so I thought I'd replace the voltage regulator. I stripped one of the bolts holding the regulator in place, so I removed the alternator. I found that the regulator was still good, but all of the attachment points to the brackets and engine were crudded over with...you guessed it, crud. I cleaned those attachment points and added a little dielectric grease to the junctures. My voltage jumped way up, even when the high load consumers were all switched on at once.

Always check those grounds.
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Casey--

'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik?

[calo1956]

Thanks to all for your suggestions, I'm going to get under there check the connections and all the wiring , grounds included and see what i can see. Ive had the motor out a few times this summer, it could be something has loosened up. Then test at the alt as you suggested
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Enjoy the ride....
72 bug
80 westfalia

[dhaavers]

FWIW, please clean the rusty ground connection at the BOTTOM of your battery box...



- Dave
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86 White Wolfsburg Westy Weekender
"The WonderVan"
<EDITED TO PROTECT INNOCENT PIXELS>

[calo1956]

Thanks Dave, thats the only thing i can say i have done already, long before this issue. The ground straps have either been replaced or cleaned as good as new, and coated with dielectric grease. I haven't had a chance to look at all the other wiring yet, or run the load/voltage tests on the Alternator yet , but will post my findings as soon as time permits. Thanks to all for there input.
_________________
Enjoy the ride....
72 bug
80 westfalia

[zuhandenheit]

[crazyvwvanman]

Yes, some places that sell the adjustable regulators foolishly say to set the voltage at the battery.
For most vehicles that would tend to be safe but not so much in Vanagons as a whole.

Mark

[E1]

I'm still thinking the battery's not holding a charge under load, but would test the alternator at both the case and on the battery, too.

Five minutes doing these are the likely cause of almost all such issues.
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[calo1956]

Will do E1, thanks for the suggestion. Will do asap, just haven't had a chance to get to it yet..
_________________
Enjoy the ride....
72 bug
80 westfalia

[E1]

Keep us posted. If unfamiliar with testing the battery while someone else cranks it over, you might go to an auto parts store and have them load test it.

We once had a house battery showing mid-12s. Its cold cranking amps was 1150, under load it showed 9. Yes, Nine, as in 10-1.
_________________
‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman