bsimon

None know of a good third brake light I can buy that won't mess with my cruse control. My oem cracked and now leaking in truck. Plz help

Dc4314

Color me curious. Why do you think a third brake light will mess with your cruise control ? They are not connected in anyway shape or form.
I am pretty sure you can buy any third brake light seal it up put it on and be ok no cruise issues or tire problems ! Lol jk man but seriously you should be fine

'08f150stx

Any third brake light brand should do. Put a tiny bead of clear silicone, the operative word being TINY just to give it an additional seal. Those seals behind the 3rd brake lights are known to leak. If you go used, get a new gasket/seal.

I too am curious as to why a cracked 3rd brake light would have anything to do with your cruise control. Let us know on that one.

djjr50

The amperage/voltage (one of them...maybe both if I remember correctly) that a light draws directly influences cruise control. If there is a difference than in those numbers, cruise control wont engage. I think cruise controls uses that to determine when you brake, which disengages cruise control.

'08f150stx

Well if that is the case I guess the simple fix without buying a replacement new light would be to just unplug the light that is there.

gone postal

Last time I checked cruise control was disabled by a pressure switch on the master cylinder in these trucks, in other vehicles it's disabled by a switch on the brake pedal.

Has absolutely nothing to do with the 3rd brake light.

BTW, if I'm wrong, and someone can toss me a schematic, it would be interesting. Ford's done stranger things than toss a differential circuit in a switch path.

djjr50

Here is a forum backing up what I was saying. https://www.f150forum.com/f4/plannin...e-light-23613/ and this one https://www.f150forum.com/f4/3rd-bra...control-51894/

gone postal

Interesting. Ford electronics strike again. What did they do, hire the guys from Lucas when the British car industry went **** up?

Mod (Ret.)

I'm assuming you are unaware that Ford uses the resistance of the brake circuit to enable/disable the cruise on/off. In days of past, they used a switch at the brake pedal to disable the cruise; now they use resistance in the brake circuit to do this, which eliminates having to use a switch (deemed dangerous, as folks claimed their car accererated on it's own, blaming a stuck cruise circuit switch). It's actually more safe to eliminate the switch and use circuit resistance.

When folks install an LED third brake light assembly, or LED taillight assemblies in their truck without load resisters built into the assembly (or manually install a load resister in the wiring), they quicly find out their cruise control becomes inoperatable. This is because an LED uses less current to light over a conventional light bulb. The cruise circuit expects a certain resestance in the circuit.

New vehicles today have gone the way of LED assemblies, and now use load resisters built into the brake circuit to compinsate for this for the cruise to operate.

Search on it here. It's been a known problem with LED bulbs and/or assemblies in the brake circuit for a few years now.

techrep

iTrader: (1)

Whay Bucko said !!