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Tue Oct 27, 2020 7:18 am

Before I begin, I feel I must say I teach basic electronic theory for the military and have a fair amount of experience in this area.

That said, I am a bit confused with this issue.

Question: I have a 1971 Beetle. I was having an issue with the Generator light staying on. After inspecting the Generator, decided to replace with a rebuilt model.

At first I was getting intermittent charging, i.e. when first starting the car at the beginning of the day it would charge. Any time turning the car on again until the next day (24hrs ish later) would NOT charge.

I also have a 1967 Beetle I swapped out the regulator from. This did not seem to resolve the issue.

I installed a brand new Import Direct OE replacement regulator. After which, the part indicated in the photos began to glow red like a heating coil in a space heater.

Any assistance is greatly appreciated.

Below are the new parts I have installed.

1. New Generator
2. New wiring from Generator to Regulator
3. New Wiring from Regulator to Battery
4. Polarized Regulator (I think, not conclusive)

Tue Oct 27, 2020 8:33 am

http://www.speedyjim.net/htm/gen.htm

Tue Oct 27, 2020 8:37 am

Guess Cusser beat me to it! I was going to erase my post but did not want to retype everything. Just edited it a little.

Never seen or heard of the regulator turning hot. Seen a lot of them go bad, but not hot.

Visit the above page and follow along. You should enjoy this with that background!

Good luck! Report back with your findings and any questions.

Tue Oct 27, 2020 8:55 am

The glowing part is the regulating resistor installed on the DF leg of the regulator. Since it's obviously getting a fair bit of current through it, I would suspect either the regulator body isn't grounded to the car chassis properly, or your transaxle ground strap isn't getting a good ground (or possibly broken/missing).

Tue Oct 27, 2020 9:00 am

Thank you kindly. I'll be trying this tonight.

Tue Oct 27, 2020 9:04 am

How can I check if the regulator is fried?

Tue Oct 27, 2020 9:10 am

JoelGothel wrote: How can I check if the regulator is fried?
Perform the generator testing as described in the speedyjim link posted earlier. If the generator passes the test but fails to work properly when connected to the VR, then the regulator or its wiring is suspect.

*edit*
You could instead bench check the regulator if you have a variable voltage output power supply. Connect the power and ground leads as appropriate per the diagram then test for proper function of the solenoids and voltage output at the B+ terminal.

On the off chance you actually only have an issue with the generator warning lamp circuit, be sure to check the charging system output in its normal configuration by measuring the voltage present either at the B+ VR terminal or across the battery terminals while the engine is running at an elevated idle.

Tue Oct 27, 2020 9:18 am

Joel, Follow the testing process that Mukluk posted here as it is well written.

Tue Oct 27, 2020 9:45 am

Much Obliged!

Tue Oct 27, 2020 11:01 am

Best option is to get the new Bosch 12 Volt Electronic Voltage Regulator it uses a Power MOSFET Diode to handle the Field Current. I have played a bit with the 6 volt Generators and the wire wound resistors for the 6 volt units are about 5 ohms and they do get hot. Probably 10 watts or so. I would expect the 12 volt regulator has a 10 ohm maybe 20 watt wire wound resistor.
Since the resistor gets its power from the Dynamo Field there is a good chance the Generator is ok but it should be charging so who knows, it could have fried the Gen and the Reg and that is just B+ voltage powering that resistor.
Here is a Schematic like the Bosch Solid State unit uses it doesn't even use that resistor just a Just a IRL3915 Power MOSFET Transistor which handles the Field current without generating much heat because it's gated on and off quickly to maintain regulation by a LMx93 voltage comparator. A little heat is generated though in the 4545 Schottky Output Diode.

Here is a photo of my homemade 6 Volt Regulator DF on the scope:

Tue Oct 27, 2020 11:45 am

Got a PCB design for that yet? Looks like a good circuit.

Tue Oct 27, 2020 12:18 pm

Somebody else posted that Splice Schematic. I did design and build my own 6 volt and 12 volt regulators but I just hand wired them and that is a lot of work! Best to just get the Bosch one or for the 6 volt something like this: VWC-113-903-801-C - 6-VOLT VOLTAGE REGULATOR (NEW SOLID STATE DESIGN).

Tue Oct 27, 2020 12:44 pm

If I remember correctly, when I resurrected my 1970 back in 2016-2017, my VR was also getting hot, and wasn't operating correctly. I bought a solid state Bosch unit and that's been great.

Tue Oct 27, 2020 12:56 pm

Having used a few or those solid-state jobs, il never go back. They're great!

Tue Oct 27, 2020 1:41 pm

Same. That or convert to a one-wire alternator :)

Tue Oct 27, 2020 1:45 pm

Really considering the alternator route

Tue Oct 27, 2020 7:06 pm

mukluk wrote: The glowing part is the regulating resistor installed on the DF leg of the regulator. Since it's obviously getting a fair bit of current through it, I would suspect either the regulator body isn't grounded to the car chassis properly, or your transaxle ground strap isn't getting a good ground (or possibly broken/missing).
I'd look into a grounding issue. I had a hard start problem and when troubleshooting I noticed the battery ground strap bolt was glowing orange. Tightened it and it stopped glowing and the hard start problem cleared up. Lucky I didn't have a fire with all the coconut fiber seat pad debris covering the area. Trans strap was clean and tight in my case.

Tue Oct 27, 2020 9:28 pm

JoelGothel wrote: Really considering the alternator route
An Alternator is twice as good as a Generator when it comes to Current! They are a great upgrade!
Just make sure you didn't switch the DF with the D+ wiring on that old generator also The price above of the Bosch Electronic 12 volt regulator is a good one if that is all that is wrong.

Wed Oct 28, 2020 12:27 pm

Status Update:

When I arrived home last evening I followed the directions I received and checked the following.
1. Performed Polarization of the Generator and Voltage Check
a. Appeared in normal limits
2. Double checked all connections
a. Solid
3. Connected battery and tested Voltage
a. Not charging Battery
4. Replaced New (Import Direct) Regulator with 2nd New (Import Direct) Regulator
a. Continued to get hot / no charge
5. End of the Day Conclusion
a. Frustration
b. Cursing
c. Rum + Coke and Smoke

Today at lunch I decided to check again the polarization etc
1. Attempted Voltage Check from Generator D+
a. 9-10 volts (Much Confusion)
2. Accidentally touched main DF Wire to something *HOT*
a. Entire wire cooked, fried, melted
b. Arced while touching main gen housing
c. Completely fried New (Import Direct) Regulator
3. Replaced regulator with 15 year old ‘spare’ Bosch Solid State.
4. Battery immediately began charging at 13.00-13.9 (14 once) Volts
5. Consistently continued charge after turning engine off and on over course of an hour.

Conclusion-
1. Bosch is best
2. Car likes pain
3. Should have taken advice and set it on fire to start with!

Seriously though, Thank you all for your help. I love that we have this community to reach out to.

Wed Oct 28, 2020 12:57 pm

I rarely need them but I always grab OG parts when I can for just such a fix. Certain things just need to be OEM on these cars.