HELP Brake switch wiring- 4L80E TCC

[fleming442]

Ok, to that goes to the purple on the F-body switch and feed the pink with pink.

 

[Injectedcutty]

Ok, to that goes to the purple on the F-body switch and feed the pink with pink.

Correct, that's how I understand it.

 

[Injectedcutty]

Alright, the plot thickens. As I was about to undo what I did I noticed another brake type switch above the normal one. It appears to have a vacuum line and a two prong plug with whattya know....a purple and pink wire just like what I need. However, I think this is a cruise control related switch, but I CAN'T LOCATE IT ANYWHERE IN THE HAYNES MANUAL SCHEMATICS!!!!
Guys, any ideas if I can tap into this instead???

 

[fleming442]

Well, here's where things get sticky. Your original cruise system was pretty much a stand alone system. If you want to retain cruise on the LS ECM, you don't need any of that crap. DBC- you need to switch over to the Tahoe/Silverado setup (see 81cutlass's build thread) or DBW- just tie the column cruise switch to the ECM. The old cruise system uses the optical sensor on the back of the gauge cluster as a speed sensor; your 4L80E has it's own built in.

To answer your question: you might be able to use the pink wire as long as it's still there (and hot) when you remove the old cruise system. The purple wire cannot be used; you'll be building a duplicate circuit for the new system whichever way you go. A lot depends on what you're doing for gauges.

 

[Injectedcutty]

Well, here's where things get sticky. Your original cruise system was pretty much a stand alone system. If you want to retain cruise on the LS ECM, you don't need any of that crap. DBC- you need to switch over to the Tahoe/Silverado setup (see 81cutlass's build thread) or DBW- just tie the column cruise switch to the ECM. The old cruise system uses the optical sensor on the back of the gauge cluster as a speed sensor; your 4L80E has it's own built in.

To answer your question: you might be able to use the pink wire as long as it's still there (and hot) when you remove the old cruise system. The purple wire cannot be used; you'll be building a duplicate circuit for the new system whichever way you go. A lot depends on what you're doing for gauges.

Gotcha, makes sense. After the last post I dug put a chassis manual and found that switch which is a cruise control release switch. I'm gonna look into wiring it a different way. My gauges are all Autometer so that doesn't help me there. I'll update my findings.

 

[Injectedcutty]

Ok, so this is where I'm at. I tested the factory switch and the pigtail with gray and brown wires is normally closed, then goes infinite or open when brake is pressed. In theory, this should work for my harness since the TCC wire just needs a +12V signal without brake applied (see pics).

My thought is to tap the purple wire to the gray wire, and once I actually have power to the car I'll re test before driving. Any reasons this won't work???

 

[fleming442]

Yup, you're good. Pink to brown, purple to gray, done. You could use the blue for a third brake light.

 

[Injectedcutty]

Yup, you're good. Pink to brown, purple to gray, done. You could use the blue for a third brake light.

Decent, also I already have a 3rd brake light, with an LED board in it so I'm good there. I'll wire up the switch tonight and move on.

 

[fleming442]

My point was that you wouldn't be using the blue for anything else. So, yeah, zip it back to the third, OR did 87-88 already have one wired? Or is that the wire for it?🤔 Things that make you go "hmmmmm".

 

[Injectedcutty]

My point was that you wouldn't be using the blue for anything else. So, yeah, zip it back to the third, OR did 87-88 already have one wired? Or is that the wire for it?🤔 Things that make you go "hmmmmm".

87-88 is already wired, mine came like that from the factory. According to the schematic there is a yellow wire that ties into the harness from the brake switch for the 3rd light.