Porsche 928 Electrics

Electrical information & supplies for late model 928s

                Porsche 928 Who Are We Wiring Diag. Primer 928 Electrics Doc Electrical Supplies Contact Us


Pulsing LED Central Brake Light:

I decided to change the central high mounted brake light to an LED bulb to get the instant switching effect (on and off) that makes LED's stand out from the incandescent main brake lamps. This subtle switching difference alone tends to draw extra attention to brake lights but its also possible to utilize a pulser module to enhance this effect. I evaluated several modules and settled on the one shown below, but as usual I modified this install a little more!

The pulser has built in a timer. If the brakes have not been activated in the last 20 seconds then on  application the bulb is pulsed rapidly on/off 5 times before assuming a steady on state. If the brakes are applied again within 20 seconds they just go directly to steady on state (this avoids annoying constant flashing in stop/go traffic.

Combined with the fast reacting LED bulb the flashing was somewhat more annoying than with a standard incandescent bulb. To address this issue I added an additional bypass resistor around the pulser so with the brakes applied the LED bulb pulses from full bright to dim (rather than fully off). This achieves a result somewhat like an incandescent yet still is more distinct due to the instant response & pulsing.

The LED bulb requires a ballast resistor to avoid bulb failure warning and this an the pulser were mounted under the sunroof cover where a good thermal connection to the inner roof skin can be made. Its actually a nearby & convenient position to use.

The LED bulb itself is a direct swap and the connection can be routed inside the hatch headliner to the sunroof area - connections can be made with easily reversible quick disconnect terminals for an easily reversible to stock project.

LED Bulb installed in the brake light  Components: flasher/pulser unit with ballast & bypass resistor


Install location for the ballast & pulser module - under the sun-roof cover


Copyright (c): Alan Moore 2006, 2007, 2008, 2009       Page Updated: 04/03/2009