Is it normal for headlights to get brighter with throttle

[Jim Brown]

and vice versa?

I know this is probably an ignorant question.

[David Jones]

Yes James, perfectly normal. If you watch the generator warning light you will see the lights start to brighten as it goes out. That is the point at which the generator starts to overcome battery voltage and as the voltage rises the lights will get brighter until the generator reaches it's max voltage which is usually around 7.3 volts with a correctly set voltage regulator. If the lights do not brighten then it is time to check the charging circuit.

[Jim Brown]

Yes James, perfectly normal. If you watch the generator warning light you will see the lights start to brighten as it goes out. That is the point at which the generator starts to overcome battery voltage and as the voltage rises the lights will get brighter until the generator reaches it's max voltage which is usually around 7.3 volts with a correctly set voltage regulator. If the lights do not brighten then it is time to check the charging circuit.

thank you sir!

It seems like each time I go to start the car (I drive it infrequently) the battery is weaker. I put a tender on it overnight Friday and it made a world of difference. Is there a chance my generator isn't working properly, and how would I independently confirm whether or not it is?

[Greg Stout]

There was a recent article in the Reg Mag, that was ALL about 356 charging circuits/ wiring/ testing etc etc....some simple, DIY stuff.
Check it out for answers to your situation.
When I store my 356 for anything over a week or so, I disconnect the ground from the battery. That usually keeps it's charge intact.
On my 912, the generator light is off when driving around, but it VERY faintly glows when I turn my headlight ON....electricity, it MAGIC !!!!!!

[David Jones]

As I said it is a very simple test to see if the battery is charging though the amount it charges depends on the state of the battery but essentially no matter the state of charge of the battery if you place one lead of a digital voltmeter on the Batt+ terminal on the regulator and the other lead to ground you will read the battery voltage. If you then start the car that voltage seen initially should increase as the revs increase and should stabilize at around 7.3 volts somewhere above 2K rpm. This confirms that the battery is charging and the amount it is charging will depend on the state of charge of the battery. A very low charge on the battery means a large amount of amps in the circuit and that can cause problems with the generator throwing solder because of overheating if you were to drive off immediately and turn on all the lights, wipers and radio though not two bad with a modern radio unless you have large speakers which thankfully most real 356 owners will be unlikely to have. A battery tender will tend to mask charging issues so do yourself a favor and go buy a cheap digital voltmeter. They can be found for less than $10 nowadays.