TheSamba.com :: View topic - Generator light on

Mon Oct 03, 2022 9:23 am

So I am in Cleveland and put my 74 Thing away for the winter and get it out in the spring. For some reason my radio and turn signals indicator lights did not work this year. I figured maybe mice had gotten into it, so I finally did some troubleshooting this weekend before putting it away. Turns out I did have one bad fuse, but the radio fuse was fine, so I did a voltage test on the hook ups and found I had -12.4 V!

A quick check showed that in my haste this past spring, when I dropped in a new battery, I hooked the positive and negative up backwards, probably because the new battery had the poles swapped on the battery itself 😳. The car drove fine the few times I took it out this summer, aside from the aforementioned items.

I swapped the connections, and bam - my radio came on. The car started up just fine however the mysterious generator light which I’ve never seen lit was on and stayed on. I parked it out of concern of doing damage to the car.

From what I have read on the site, I have either:
1. smoked the voltage regulator, or
2. need to re-polarize the generator, or
3. possibly replace it, or
4. A combination of 2 of these things

I’m not sure where to start or how to necessarily test what May be wrong. Appreciate advice from anyone regarding how to proceed here. Thanks so much!

Mon Oct 03, 2022 6:23 pm

I just upgraded to an alternator. I was sick and tiered of the generator/regulator setup. The alternator is working like a champ. No more dealing with faulty regulators burning unrelaiable generators.

Here you have a video on how it is done.

Follow my Youtube Channel.

Mon Oct 03, 2022 6:43 pm

Thanks for the tip. I consider that option c. If there is a cheaper part to replace, or simply a polarization process I need to do, that would be preferable. What is the advantage of the alternator?

Tue Oct 04, 2022 8:50 am

cwaff wrote: Thanks for the tip. I consider that option c. If there is a cheaper part to replace, or simply a polarization process I need to do, that would be preferable. What is the advantage of the alternator?

Alternators produce a stronger and more consistent charge than generators. They also have an interior voltage regulator giving the opportunity to get rid of the voltage regulator in total. Generators are usually smarter options with cars that run more accessories like stereos, lights, etc to keep up with the load, even at idle.

I would assume you smoked your voltage regulator. If the car runs, you can test if it is supplying power to the battery by getting a voltage reading on the battery terminals while idling. It should read at least above 13V showing it is charging the battery. You can also test the voltage coming off the generator to rule the generator out.

Tue Oct 04, 2022 9:13 am

Thanks for the tip I will give this a try. What are the contact points where I test the voltage coming off the generator.

Secondly after reading about generator polarization a bit I was surprised because I never really knew that was a thing. None of the posts said anything about hooking up batteries backwards - so Im wondering if a reverse polarity hookup had the generator spinning the wrong way and I need to polarize? Like perhaps that is the source of the light? Open to any thoughts here.

Anyway, thanks - I will report back!

Tue Oct 04, 2022 12:26 pm

Ok update:

- engine is running clockwise
- have 12.4v at battery when car off, 11.5 when car is on
- measured at the 2 poles of generator when running, I got intermittent voltage of line 5-6volts but it jumped a bunch.

Does this help? Do I need a voltage regulator because reverse polarity ruined it? Like I said, car runs fine, gen lite is on.

Thanks!

Tue Oct 04, 2022 3:21 pm

You probably fired both regulator and generator when you hooked it up backwards....

I would change to alternator... plus... my old generator was 30 amps, my new alternator is 55 Amps.... plenty of "Juice" to run ligths and accesories.

Tue Oct 04, 2022 4:16 pm

Alternator is needed when you are hooking up a lot of electronics that need the extra juice. If you are keeping everything stock there's not a whole lot of benefit. If you plan on adding a big boom box, lights, and other electric needy items alternator is the way to go.

Read through this and it will show you how to test all the components of your charging system. I'd start with the generator to make sure it is good. Then you can work your way to the regulator. A new Bosch solid state regulator should be less than $50 shipped.

http://www.vw-resource.com/generator.html

Tue Oct 04, 2022 6:27 pm

Generator brushes possibly

Wed Oct 05, 2022 8:25 am

Thanks for the tips!

For the record I just have a basic radio in place nothing fancy, and the car has run since 1974 just fine, and runs now. Not looking for an upgrade per se - watched a couple videos on what is involved in switching to alternator and not looking to go that deep unless I have to. I simply have the red Gen light on, and car runs, but apparently battery is running everything and is not being charged due to my reverse hookup.

Unless anyone has other ideas, Im thinking I start with a voltage regulator and see if that does it. What should i be measuring at the poles of the generator? Anyone have more ideas about diagnostics i could run to check the problem.

Thanks!

Wed Oct 05, 2022 8:29 am

You should check the generator brushes
Theres a procedure to do that and its very simple

Wed Oct 05, 2022 8:45 am

cwaff wrote:
Unless anyone has other ideas, Im thinking I start with a voltage regulator and see if that does it. What should i be measuring at the poles of the generator? Anyone have more ideas about diagnostics i could run to check the problem.

Thanks!

Did you look here? http://www.vw-resource.com/generator.html

I have followed that tutorial so I know it works. It's quite easy and straight forward.

Wed Oct 05, 2022 4:50 pm

Hi from the west side of Cleveland from another 74 driver! If you check your generator brushes and find they are worn down I think I have a new pair in my parts box you could have if you are nearby. I ended up with an extra pair. 12.4v feels like it might take some driving time to keep the battery charged up.

Thu Oct 06, 2022 11:28 am

Hey cleveland guy - appreciate the offer - we will see if it comes to that!

Thu Oct 06, 2022 11:32 am

Quick note to folks suggesting reasons my generator went bad/putting out 12.4V (basically = battery power and 0 from alternator) - please read above - my situation is not one where this wore out! It is instead a case where everything was good until some dummy :roll: hooked up his battery backwards and drove it for a summer.

Im looking for some logic to see what this likely broke/damaged since the engine continues to run fine regardless of battery polarity, but since I reversed the poles so that it is correct, the generator light is on.

Im hearing voltage converter - anyone have a source or other logic as to why reversing battery polarity would cause gen light to go on?

Thanks!

Thu Oct 06, 2022 7:34 pm

Good lord man! Follow the link that heimlich gave you. It TELLS you what your problem is.