Something funny with the charging system

[Hydro626]

72 Super beetle, been basically dailying it for months, recently the gen light likes to stay on after I start the car sometimes. Usually I'll rev the engine or start driving and it turns off.

This afternoon I was trying to diagnose a slow idle that's appeared over the past week or so by checking voltage at the + terminal on the coil and found 11.9 volts 😳. I go check the battery proper and it's only slightly higher, about 12.2. I also notice that the generator light is on this whole time, but the gen is definitely spinning. I rev the engine and the voltage doesn't change. I try this a few times before finally revving it up pretty high when it finally jumps up to 13.5 volts and the light on the dash turns off. The voltage then stays in the 13s even when it returns the idle. Still, for a few minutes there the voltage was in the low 12s, the gen light was on and revs didn't change it.

Some probably pertinent information:
- I recently changed out the ignition switch wiring harness because I discovered the old wires weren't actually wired up correctly and were getting hot with the lights on(ignition was running off the headlight fuse ¯\_(ツ)_/¯). Everything is now where it should be and all the connections are clean and tight.
- I replaced the voltage regulator last year and haven't had any trouble with it since (unless this counts)
- might be totally unrelated but my fuel gauge is INSANE lately. Either it's reading all the way full or the needle buries itself out of sight to the left, or it's bouncing between the two as I drive. I think the vibrator's gone out. Figured I'd mention it here.
- battery is at 12.6 when the car isn't running.

Please note that the gen light staying on after the car starts was occuring before I ever messed with the ignition switch wiring, and is what prompted me to investigate this issue in the first place.

Could it be that I just need to tighten the belt? It's got a little slop in it. Could this also be what's causing my rough idle? Sorry if this is a lot
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1972 Volkswagen baja Super Beetle "Elizabeth"
1989 Cadillac Brougham D'elegance

"Never name your car...too much unhealthy emotional connection coupled with your human dark/light,yin/yang energy affects the mechanical health of the vehicle and causes magnetic convergences like the one you just had.that, or some old f**k backed into your car,its hard to tell..." -johnnypan

[67rustavenger]

Have you checked the condition of the gen brushes?
Start the engine a put some revs to it when checking the voltage at the battery. Generators really don't charge at idle.

While your back there with the tools. Rotate your generator 90° CW. The way it's currently set, the cooling vent is blocked. It needs to point straight down.
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I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[Cusser]

https://speedyjim.net/htm/gen.htm
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Hydro626]

So I tightened the belt and that definitely seemed to help. Voltage readings were higher across the board and the gen light went out almost immediately when the engine started. I think I may have put the cart before the buggy on this one and my real issue is now my low idle which results in low voltages. I've removed and blown out both the jets from the side of the carb with no change, which is what had me leaning toward a voltage issue, but I may have mistaken the effect for the cause.
_________________
1972 Volkswagen baja Super Beetle "Elizabeth"
1989 Cadillac Brougham D'elegance

"Never name your car...too much unhealthy emotional connection coupled with your human dark/light,yin/yang energy affects the mechanical health of the vehicle and causes magnetic convergences like the one you just had.that, or some old f**k backed into your car,its hard to tell..." -johnnypan

[Hydro626]

Dropping ~.2 volts across the wire from the fuse box to the coil shouldn't make it idle weird right?
_________________
1972 Volkswagen baja Super Beetle "Elizabeth"
1989 Cadillac Brougham D'elegance

"Never name your car...too much unhealthy emotional connection coupled with your human dark/light,yin/yang energy affects the mechanical health of the vehicle and causes magnetic convergences like the one you just had.that, or some old f**k backed into your car,its hard to tell..." -johnnypan

[passionre]

[Hydro626]

[Hydro626]

So I went out to mess with it today and had another situation where the generator light stayed on for a few minutes when I first cranked it up. Checked the voltage at the battery and it was 12.2 with it running. Revved it and it didn't change. Revved the crap out of it and it finally climbed into the 13s and the light went off. After that it seemed fairly stable. Still sort of concerned that it took heavy revs to get it to act right. It didn't start doing this until recently
_________________
1972 Volkswagen baja Super Beetle "Elizabeth"
1989 Cadillac Brougham D'elegance

"Never name your car...too much unhealthy emotional connection coupled with your human dark/light,yin/yang energy affects the mechanical health of the vehicle and causes magnetic convergences like the one you just had.that, or some old f**k backed into your car,its hard to tell..." -johnnypan

[ashman40]

Don't expect to get any meaningful charge voltages at idle. Raise the rpms to at least 2100rpm before you take a voltage reading.

Did you check the condition of your generator brushes as suggested above? Do they move freely in their slots. Also check the tension in the spings that apply pressure on the brushes. The inconsistent nature of your problem points to a bad connection which bad brushes could be the cause of.

Read the link to Speedy Jim's page on the charging system. Test the generator output when you bypass the VR and ground the DF terminal. This forces the generator into max output for a few seconds. The voltage out of the D+ terminal on the generator should spike well above 35v+. This confirms the generator can produce sufficient voltage and you should turn your attention to the VR. But if grounding the DF terminal does not put out lots of voltage you know the problem is within the generator.

If the testing suggests the generator is capable of outputting enough voltage and you decide to replace the VR, be sure to buy the newer solid state Bosch VR and not the older/OE style mechanical points VR.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[Hydro626]

[bsairhead]