Flickering headlight

356 Porsche-related discussions and questions.
Post Reply
Message
Author
Peter Poulikakos
356 Fan
Posts: 125
Joined: Tue Apr 15, 2008 1:09 am
Location: Sydney Australia

Flickering headlight

#1 Post by Peter Poulikakos »

Hi All
Hoping someone can shine some light on my situation.
I have a 1959 356a, 6 volt generator (working correctly).
I have led/smd headlight globes. At idle the right globe flickers, the left does not flicker(works fine). Once the engine is over 1200 rpm the globe no longer flickers. I have swapped the globe with another and checked connections at the headlight, still flickers. Not sure what I should check next.
Thanks in advance for any assistance.

WilliamVaughan
356 Fan
Posts: 446
Joined: Fri Dec 03, 2010 7:42 am

Re: Flickering headlight

#2 Post by WilliamVaughan »

It is likely that an LED based headlight uses a switching power converter to stabilize the current to the LED string.
Switching power converters behave like negative resistance devices. They are often constant power consuming devices. If you decrease their input voltage they do not decrease their input current draw. Instead, If you decrease their input voltage they increase their input current draw. They become current hogs at low input voltage. Likely your right side LED lamp assembly is experiencing high source resistance in the right side supply wiring or grounding. The generator voltage rises and falls in proportion to engine RPM. The switching power converter is exhibiting some sort of input threshold voltage sensing. It may be a part of the power converter design or accidental. I think you must treat the LED lamp much like a conventional tungsten lamp. You could use a tungsten lamp in the right side and a DC volt meter and search for the source of the voltage drop.

Post Reply