Quote:
Originally Posted by RSBob
They also offer resisters which may help for cruise control users, but have not verified. Without the resistors I can tell you as a fact (tried them on my SC) cruise is disabled. The pigtail solution above may provide the feedback which cruise needs, but again, unverified.
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After working with some folks here, we've found the maximum ballast resistance to satisfy the 1989 911 CC is somewhere less than 10 ohms. Thus 6 ohm ballast resistor will satisfy the CC ECU.
From SuperbrightLEDs, here's a typical 6 ohm, 50W pigtail designed to alleviate hyperflashing when changing turnsignals to LED. You simply crimp these on to the bulb wires.
Can this pigtail be used for the brake light to satisfy the CC? The answer is: "It depends"
It depends if you mount the resistor securely on a part of the vehicle chassis to act as a heat sink. Putting 6 ohm resistor across battery voltage like when you put your foot on the brake will burn:
14V x 14V / 6 ohm = 32.7W
These resistors are rated for 50W if the resistor is connected to a heat sink. If the resistor is not connected to a heat sink (or vehicle chassis as a heat sink) then it's power must be derated to 40% of maximum or 20W.
20W is less than 32.7W so one resistor will get extremely hot when on brake and possibly destroy itself. If one puts two 12 ohm resistors in parallel, then each resistor burns 16.3W and should be ok.
For turnsignals, this one 6 ohm resistor is ok because turnsignals are on only 1/2 the time when flashing thus burning 16.3W and should be ok w/o a heat sink.
One thing I'm not a fan of with these crimp-on resistors is the fact you have to damage vehicle wiring to install. Not a big deal but I try to make every solution such that no permanent vehicle mods need to be done to install.
As previously shown in this thread, the pigtail I would suggest would simply connect between the brake master cylinder brake light switch and its plug. The pigtail uses two 12 ohm resistors in parallel to share the power dissipation and heat.
If you're ok with a crimp tool, you can easily make this pigtail. Resistors can be purchased online from places like Digikey and Mouser. If you would like to purchase the pigtail, we'll make them available for $20 each.
