Alan

It isn't zero when cold - it is about 1/10th of its full hot resistance. I have no idea what the minimum to work is but stock is ~63W so perhaps a more decent proportion of that. If you started with a warning bulb that could be as low as 1.2W so you can see it can be a very big difference. Earlier in the thread Borland/Ed confirm that a single 21W brake bulb (in the CHMSL) was enough - so presumably the minimum is less than that...

We also know from Ed that a 6 ohm power resistor works fine - just use that.... see mounting recommendations.

Alan

Ed Scherer

6 Ω resistor worked, 25 Ω didn't. I still haven't reverted my solid state solution to a power resistor (you can't expect me to get around to a big job like that in only six years ), but when I do, I'll probably experiment a little more to see if something > 6 Ω but less than 25 Ω will work (12 Ω using a couple of 6 Ω resistors in series would be an easy experiment and would spread the heat out across more heat sink area, too). I really don't like converting electricity to heat unnecessarily.

scoper

I read through most of this thread but am not electrically inclined. It also confused me because it seems at least 2 topics are intertwined in it. I have LEDs in my 78 brake lights (pre CHMSL). I have a freshly rebuilt CC unit and the CC works but as soon as I trigger it the red warning dash light comes on as well as one in the control panel. I want to have CC without the red light, and I want to keep the LEDs. If I install a 6 ohm resistor (Superbight LEDs RL-650-K) in parallel with the brake light circuit, should I expect to get what I want?

Ed Scherer

I'd say probably, but maybe there's something else going on.

What warning lights are turning on? (I'm not very familiar with the pre-S4/GT cars)

scoper

In addition to the red warning light in the pod, the brake pressure light gets lit.