[T3] Lights

Jim Adney jadney at vwtype3.org
Sat Nov 4 08:15:47 PDT 2017

On 4 Nov 2017 at 1:04, Dave Hall wrote:

> I see that there are special flasher units for LED turn signal lamps -
> presumably as the old relay no longer senses the larger load that was
> provided by the filament lamps. The alternative seems to be adding a ballast
> resistor to mimic the filaments.  Anyone confirm that? 

There are 2 aspects to this:

A resistor would give the load that an operating bulb would draw and make 
an old fashioned (the kind with a thermal heater) flasher run at the proper 

But our flashers, at least the 12 V ones, have another feature that senses 
that a bulb has burned out and flashes faster then. This is because a 
tungsten filament draws a LOT more current when it's first turned on and is 
cold. The initial currrent is 4x-8x as much as the normal operating current. 
Our flashers sense this overcurrent and use that to trigger the normal flash 
rate. A resistor won't do this.

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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