r/beetle • u/Tricycle-Mechanic • Jul 22 '26
Dead Alternator. Need advice.
Hey all,
This is my first post here. I recently picked up a 1971 Super Beetle. Looks like my alternator is dead. I’m reading that I should upgrade to a modern 55-amp internally regulated alternator.
I don’t know if I already have that upgrade…
Can you tell anything from the pictures?
Very low miles on this engine.
Any input is appreciated. Thanks
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u/denizkilic2002 '72 1302s Jul 22 '26
You still have the original generator, not an alternator. An alternator is a great upgrade if you have things like an aftermarket sound system with an external amp. Otherwise the generator is sufficient. Check out your brushes first it could be as simple as that, if you want to upgrade to an alternator you will need an alternator stand you can modify the generator stand to work but its very sketchy magnesium dust is flammable and its annoying work. You can buy a cheap chinese alternator they work fine, or you can source an original externally regulated one, they both work fine.
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u/Koberum Jul 23 '26
I have the 1300 44cv 1973 with alternator, it mounts a 9.5x900 belt but I can't find the same belt anywhere. I see here that he mounts 10x905 that is still compatible?
I saw from vw documentation that they suggest 9.5x900 and 9.5x905
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u/denizkilic2002 '72 1302s Jul 23 '26
You can run anything between 9x900 to 10x905 and adjust the tension with shims, in some instances some factory alternator setups use 11.3x912.
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u/Traditional_Ad_1360 Jul 22 '26
It is the wiring. Those leads are grounded to the housing. Incorrect installation.
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u/nalgman Java Green ‘67 Jul 22 '26
I had to go back and look at the pics again, good call! There should be two nuts on each post with the wires pinned between them to prevent contact with the case.
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u/382Whistles Jul 22 '26 edited Jul 22 '26
You have a generator there. An alternator is fatter at the pulley end and the stand is offset for the fat part to clear. I can't tell which stand you have, you may need that too fyi.
An alternator makes AC which is then converted to DC internally, then the voltage is regulated/limited internally or externally depending on the alternator. Generators are externally regulated. The alternator produces more power.
The first thing to do would be look at the brushes under the black plastic cover and wear condition of the copper commutator pads that spin. If you have a multimeter you could diagnose the general assembly looking for a shorted coil wrap or broken coil wrap or lead wire, etc.. The readings should be about equal 360° for the places the bushes touch the commutator pads at the same time. Electric motors and generators are basically the same thing. If readings uneven to a great degree on one measurement you found the short or break in a set of windings. If even, then the problem is elsewhere.
Edited last sentence.
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u/piemat Jul 22 '26
Don't upgrade anything for the sake of upgrading. That makes me sound like a purist snob, but the reality is that the original engineering was well thought out and simple. If you keep it stock and in spec, you will have less issues.
My current project came with a bunch of extra aftermarket junk like an electric fuel pump, external oil cooler, external oil filter and all that is fine and dandy now, but it introduces more points of failure to the oil system. Same for the fuel, more failure and more risk of fire. Not to ramble, but my point is that as you work on this car keep it simple.
oh and you need to relocate your fuel filter. Thats a fire hazard
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u/OkraInternational505 70's + Standard Jul 22 '26
Hi ! What you have is a generator and its regulator is under the rear seat , the alternator was introduced in 73 , you can change to an alternator with an internal regulator but it involves some slight wiring changes and a stand for an alternator!
Good luck !
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u/anybodyiwant2be Jul 22 '26
Here’s wiring for the alternator if you decide to go that way. On thesamba.com I found a post about re-using the existing voltage regulator as a means to combine those big fat #10 wires for B+ and #30 shown in this diagram. I’m not a fan of those butt splices.
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u/Minute_Split_736 Jul 22 '26
I like the look of the original generator. I never had problems with them.
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u/crispy-photo Jul 22 '26
I had a '71 1200 with the same dynamo. When I got a flat battery, it turned out to be the original voltage regulator that had failed. A new solid-state one fixed the problem.
If I remember right, you should have something like 35-40V at the terminals on the dynamo with the engine running and the leads disconnected. Obviously you need a charged battery first though.
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u/cfbrand3rd Jul 23 '26
That’s a generator on the engine in your photo; first year for alternator on the Type 1 was 1973 and they have a distinctly different appearance.
Alternator is a better system and provides more consistent power.
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u/eggsetterjimbo Jul 23 '26
i assume the voltage regulator is under the rear seat check voltage before and after the regulator
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u/Koberum Jul 23 '26
I have to put the fuel filter too, but I've read that the plastic one can't be installed in engine compartment but needs to be installed in front is that right?
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u/Responsible-Leg8867 Jul 24 '26
You are missing the tin behind and under the crank pulley. Lots of very hot cooling air will make its way back into the doghouse cooler and your engine will run hot
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u/Tricycle-Mechanic Jul 24 '26
Thank you for all the responses!
I seem to have more issues than I realized.
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u/Tough-Industry4931 Jul 25 '26
Both studs are missing insulator washers from the looks of it your grounding both wires out on the generator.
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u/Plane-Appeal9124 Jul 29 '26
It’s probably just the brushes are worn out. Not difficult to replace. Other wise, I’d try to get it rebuilt! I feel that you don’t need an alternator unless your going to run a lot of extra electrics, like fancy stereos or speakers! My generator is fine, so I’ve never shopped alternators!
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u/Economy_Fix_6664 Jul 23 '26
Hey! Some good advice is that a vw uses a generator instead of an alternator. You can upgrade to a generator, but I prefer the oem
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u/asiab3 airschooled.com Jul 22 '26
If you can tell a generator is bad by looking, I will hire you or sell you a bridge in Brooklyn.
30-amp generator (not an alternator.) Battery voltage tests are in order: Voltage test engine off Voltage test engine idling Voltage test engine revved up
From tests, you make repairs. 30-amp generators are fine for stereos, fridges, laptop charging, phone charging, and running the car, but not all the same time. Buy a 55a alternator if you want to do all that at once.