Ferdinand Porche's Magic Smoke

The Beetle is coming along slowly. I have been spending my time in the engine compartment tuning the engine so it likes the new carburetor I just installed. Tuning the engine is nothing like tuning a piano. It’s much louder and requires standing over the non-emission controlled exhaust pipe while I rev the engine -probably not the best thing for my health.

The engine's mechanical components are behaving relatively well but while it was in storage for the last couple of years a new problem developed. Humor me a bit while I give a little lesson about VW’s…

There are two a total of six lights on my dashboard.

• One is so I can see the speedometer and fuel gage at night.
• A second is on the radio (which had the serial numbers filed off).
• A third tells me when I have turned on my turn signal (in either direction).

Since VW didn’t design the dash with separate left and right turn signals you would be correct to assume they didn’t waste the other three lights on reminders for routine maintenance items. Of those three lights:

• One means that half of your brakes have failed. (not all your brakes though, the sensor only measures the pressure differential between the front and rear brake cylinders. VW assumes any idiot can figure out that all the brakes have failed so it doesn’t need a light)
• Another light informs you the oil pressure is less than 10% of what it should be. When Ferdinand Porche wasn’t designing the Panzer and Tiger tanks for Pre-War Germany he was put to work on “the people’s car.” Porche thought a radiator would be excessive for the practical German Folk and put in an extra-big oil cooler so the engine’s own oil would be its coolant. If this light comes on for more than a split second in a turn when the oil is sloshing around it means the engine has no coolant and is about to turn itself into a block of Aluminum-magnesium alloy.
• The final light tells the driver that the generator has stopped generating power. The generator recharges the battery so if this light comes on it tells you the battery is the only thing running your spark plugs and the engine will stop running once the battery runs out. In his enthusiasm for liking systems together Porche also extended the shaft that turns the generator through the generator and installed a big as fan on the other side to blow air past that extra-large oil cooler I mentioned. The generator light coming on can also mean the belt that turns the combination generator/fan has broken and there is no air cooling that oil which prevents the engine from to turning itself into a block of metal.

It was the final light that came on. Luckily for me the belt has not broken so Porche’s monster lives, for now.

A test with a volt-meter confirmed, however that the generator is not charging the battery so if I want to drive it anywhere other than my driveway I’m going to need a battery charger and an extension cord.

Another aside: If you know cars you will notice I didn't say "alternator" before, until 1973 beetles got their electricity from a DC generator. Most cars today use an AC alternator with a rectifier to turn the power back into DC. If you are intrigued by the generator/alternator debate there are lots of pages about it on the internets; I will spare the rest of you.

Anyway the generator has a charged coil of wire, which is rotated through a magnetic field that is created by a stationary coil of wire. Changing the voltage in the stationary "field coil" changes the strength of the field and the power output of the generator. A voltage regulator underneath the beetle’s back seat (next to where I stow my jumper cables) controls the field voltage. Right now it isn’t sending any voltage to the field so I don’t get any energy out of the generator.

The regulator isn't solid state, it has two electro-magnets with spring loaded contacts and resembles an old telegraph. With a constant field generators create more power as you spin them faster so when the regulator is working and I rev the engine it quickly opens and closes contacts to reduce the average current flowing through the field coil. This has the side effect of creating a clicking sound under the back seat when I rev the engine which is very assuring to my passengers. :)

The reg seems to be broken so I disconnected the car’s battery and tore the cover off last night to poke around inside and see if anything was obviously wrong. Everything seemed good with the power off so I cleaned off all the contacts reconnected the battery and tried poking it with a screwdriver while the car was running. (Poking at live circuits is probably not the smartest thing in the world to do but it’s a 12V system so in theory it can’t hurt me too much) For once I was glad all this electrical stuff was under the back seat since I could play with it while the engine was running and still see the generator light on the dashboard.

A continuity test showed me one contact is suspiciously closed no matter where it is positioned. I didn’t touch that one in this test. Instead I closed the other contact which was normally-open. There was a mild blue spark but it did get the generator light to go off. Impressed by my initial success I shut the engine off.

With the engine off, however the generator light was still on and magic smoke seemed to be finding its way out of the regulator. Having read the generator light being on when key is off means the battery is trying to turn the generator like a motor, and knowing magic smoke getting out is always a bad thing I pulled the negative strap off the battery again to kill all the power in the car.

Post-mortem examination revealed closing the contact by hand allowed the contact to weld itself shut. It was easily opened again but at present I am not any closer to getting the regulator to work; if it was kind of dead before it’s probably really dead now.

Luckily new regulators are only about $30 but I would like to figure out how this thing is supposed to work. If anyone finds wiring diagrams for electro-magnetically controlled 12V generator voltage regulators let me know. In the mean time I hope your summers are going well.

No Worries