Alternator/Electrical Problems 73 Super- Help/Exorcist Needed

[revivingvw]

Just as some background, I have had had my '73 Super Beetle for a little over 9 years, and the electrical system has always been a disaster (and I have turned to the nice people on the Samba to fix many things over the years).

My current problem is that the externally regulated alternator is not charging. The "G" light comes on when the key is turned to "on" and goes off at idle. However, when I increase the RPMs, the light comes on and gets brighter.

I currently have what I believe is a Bosch alternator (pictured below before dual carbs were added), but I cannot seem to see brand name, though I know I have seen it in the past (it does have a VW logo and part number on it). I had it rebuild probably 5 or 6 years ago, and I checked the brushes today. They seemed to be good.

The battery gets around 12v across the posts when off, and nothing seems to change when the car is running at any RPM. I also hooked it up to one of those home jumper/alternator testing kits, and it came back as failed as well. Last week, a mechanic friend (Who I owe a whole truckload of beer and/or pizza) and I bypassed the regulator for a short time by jumping some posts on the alternator itself, and the alternator testing kit went from "failed" to "good" when the wire was jumped. I have replaced the regulator (thinking that was the problem) with the same one it had from parts Geek https://www.partsgeek.com/catalog/1973/volkswagen/...mersedview.

When wiring it up, we connected the 3 wires from the alternator, a wire to the positive battery post, and the "G" light wire though the connector in place.

Before replacing the old regulator, the "G" light would be on constantly (even with the key out of the ignition), except when the car was running. Now it works as normal at idle.

Where the problem gets even more interesting, is that I am in the middle of replacing the wiring harness with a kit from Rebel Wiring https://watsons-streetworks.com/product/rebel-wire-v-w-bug-deluxe-wiring-harness/.


After trying to diagnose the first problem (detailed below) I decided it was time for a full upgrade (for my sanity ) The kit has been fairly nice and replaces 99% of my junk wiring with modern upgrades and a modern fuse box. Plus the '73 super harness is darn near impossible to find and I am no purist.

Almost two months ago, I took the car out for a drive and noticed a few weird wiring issues that were out of the usual. The turn signals blinked quickly (even though they all came on) and the radio would cut out when I hit the gas and back on when I hit the brakes. I had just but the back seat back in, and I figured the speaker wires may have been smashed, no big deal. After driving the car across town, I get back in, and start it just fine.

I then pulled out onto a fairly busy street pretty quickly and the "G" light came on when I put the pedal down. I thought I might have thrown the belt, but after I pulled over and checked, the belt appeared to be fine. I figured it was still cooling and decided to drive it home.

As I accelerated the "G" light got brighter and brighter then blew the speedo bulb and the fuse for the taillights. From that point forward, I couldn't get the light to come on (even when replaced) or the alternator to charge.

Now, as my friend and I rewired the ignition, it seems we are having the same problems, and I don't even know where to start!

I appreciate all the help I can get!

Other details: 1641cc (Rebuilt 2014) with dual Empi 34s (installed spring 2017). It was hit a few months back lightly on the driver quarter (right by the regulator), but was repaired by the local restoration shop and was driven since. I did notice a bolt on the fender was missing that could have let water in around the regulator, but it is doubtful since it is garage kept and a fair weather driver.

TL:DR- I love my car, the wiring is a mess, send help.

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_________________
'73 Super Beetle, '15 Golf Sportwagen TDI

If it isn't broken now, it will be soon.

-Dylan

[theKbStockpiler]

Get a voltage gauge or install a volt meter and ignore the light. I think the light comes on when more current is flowing from the battery than into it indicating the charging system is not working and it is running off the battery. You should have 13.5 - 14.5 volts when running.

Get the charging system to work right first and then treat the rest of the wiring as a short.
http://www.vw-resource.com/alternator_generator.html
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My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[revivingvw]

Thanks for the resource. I’ll look at that. I tested the battery with a voltmeter and got the same 12.5-6 volts with the car running and at various RPMs.

I guess my questions would be:

Why would the light not be on during idle but come on and get brighter when I increase RPMs?

How could I test to make sure the alternator is good?

Is my alternator bad?

Thanks!
_________________
'73 Super Beetle, '15 Golf Sportwagen TDI

If it isn't broken now, it will be soon.

-Dylan

[Dark Earth]

Do you have a transmission ground strap installed ?

It basically grounds the rest of the chassis to the engine and transmission. Without it, the rubber motor mounts and transmission mounts insulate the transmission and engine from the rest of the car causing grounding issues.
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My Build: '69 Baja - Dark Earth Version

~I'm almost done. I just lack finishing up.~

[theKbStockpiler]

If your running volts is not higher than you sitting volts the charging system is not working at all. Now you have to do checks to make sure that the system has the support of other things to work like complete electrical paths and voltage at terminals where it needs to be.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[ashman40]

For a detail step-by-step procedure for troubleshooting the externally regulated alternator see this page. The VW Beetle externally regulated alternator was identical to the Porsche 914 alternator setup described here...
https://www.pelicanparts.com/techarticles/914_alte...eshoot.htm

How the GEN light works:

1) One side of the GEN lamp is powered from the ignition switched 12v+ circuit (#15). The other side of the GEN lamp is connected to the voltage regulator (VR) via the blue #61 wire.

2) There needs to be a sufficient voltage difference present in the two bulb connection for current to flow thru the bulb filament. If the voltage difference between the two bulb wires is too low the bulb will not turn ON; not because of a lack of voltage but because the current flow is too low. Normally, voltage is measured between the power source and ground (ground = 0v). But this is not always the case with the GEN lamp.

3) While the alternator is NOT spinning the #61 wire is grounded thru the field circuit of the alternator. This is why the GEN lamp turns ON with the ignition before the engine is started. The voltage coming from the #15 side is 12v+ while the #61 side is ground (0v). The voltage difference is 12v so the bulb turns ON as current flows thru the bulb filament.

4) While the alternator is spinning and charging, the D+ circuit of the VR will feed 12v+ into the same #61 wire. This continues to power the field circuit and allows the alternator to create a charge. It also back flows 12v+ up #61 wire towards the GEN bulb. This means the GEN lamp now "sees" (around) 12v+ coming in from BOTH wires. With positive (+) voltage coming in on both bulb leads the difference in voltage potential between the two wires drops to (nearly) zero-volts. This means there is an insufficient current flow thru the bulb filament for the lamp to turn ON. And yet, if you measure the voltage difference between either side of the bulb and a good ground you will still measure 12v+! This is an example of there being voltage at the bulb but no current flow.

5) The bulb will only turn ON to warn you when the current flowing through the bulb is enough to heat up the filament and cause it to glow. More current and it glows brighter. Current flows where there is a voltage difference on the two sides of a device in the circuit. The (incandescent) GEN light does not know in which direction the current is flowing. It doesn't care. As long as there is a flow of current (caused by the difference in voltage potentials on either side of the bulb) the bulb will turn ON. This means that the bulb can turn ON when the alternator output is too low or too high, or if the battery output is too low. Either of these conditions cause current to flow thru the GEN lamp because there is a difference in the voltage coming from one side of the bulb.

_________________
AshMan40
---------------------------
'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!}

[revivingvw]

Thanks for the help all! I have been crazy busy with work, and hope to get back to the car this coming week. I will keeo everyone updated!
_________________
'73 Super Beetle, '15 Golf Sportwagen TDI

If it isn't broken now, it will be soon.

-Dylan

[revivingvw]

Hey everyone, I am at my wits end with this thing. I checked over everything that was suggested, and I am still having the same problem. The alternator light comes on with the key, goes off with start, and then comes on as RPMs increase. This happened both before and after I upgraded the wiring harness, so I am starting to think it has to be the alternator as it is the only thing that has not been replaced.

I replaced the battery as it was shot, no change. I triple check the charge with a voltmeter and the car is not charging while running. It keeps blowing the 2 watt bulbs in the speedo and I am not sure why. I checked the brushes (the alternator was supposedly rebuilt about 5 years ago), and they seem a bit worn/ there appears to be some corrosion inside. I replaced the external voltage regulator, and no change as well.

I also do not appear to have a ground strap on from the engine/transaxle to the chassis. Could this cause the problem?

Is it time to replace the alternator? If so, do they have externally regulated alternators for sale anywhere? I only seem to find internally regulated alternators.

Thanks!
_________________
'73 Super Beetle, '15 Golf Sportwagen TDI

If it isn't broken now, it will be soon.

-Dylan

[David_nc_72std]

Just a thought, have you checked to make certain the battery is connected properly, with the terminal marked (-) going to the ground strap?

[Q-Dog]

[PuddleRainbow]

Ashman does it again. The GEN light info is awesome. Thanks very much.

[jamin12369]

[ashman40]

Did you read the Pelican Parts link I provided above? Towards the bottom of that article it describes how to troubleshoot the external VR alternator charging system. All you need is a voltmeter and a jumper wire long enough to reach the battery. The tests basically bypass the VR and check that the alternator output Follow these steps and report back (in detail) what you find.
_________________
AshMan40
---------------------------
'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!}

[revivingvw]

Hey all! Thank you for all of your help, and I wanted to post a reply in case anyone else was following.

After trouble shooting with all of the resources, I ended up replacing the alternator which solved the problem. In fact, when I removed the alternator, pieces of it fell out

She's back out on the road!
_________________
'73 Super Beetle, '15 Golf Sportwagen TDI

If it isn't broken now, it will be soon.

-Dylan

[74vocho]

Revivingvw, do you have the schematic of how to bypass the regulator? I’m also re doing my harness but with American Autowire harness. And I upgraded to an alternator, and don’t need the regulator anymore. But don’t know how to bypass it. If any of you have answers, I would really appreciate it!

[Cusser]

[74vocho]

[74vocho]

Haha jk I just saw it on the schematic. Thank you guys. I’ll keep you guys posted if I need any more help. Wish me luck. Thank you again.

[vamram]

Glad you got it working. Did you install a ground strap?
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[74vocho]

Not yet. I just started today. Did most of the wiring to the engine. It took me a while to figure out a spot of where to put the new fuse box, that was a challenge, not very happy of it and I might move it again. Where is a good spot to hide the fuse box? I have a 74 super.