I'm glad i could help

 

ONLY one question:
Acording to the written by Texas and with the diagram from BlueMule, I thought was the same , BUT are exactly the opposite ; Im confussed now: it can be done in either way, it doesnt matter, or what is the correct?

 

Either way will work .. your call.

85 - 86 is the relay coil.
30 - 87 is the relay contacts.

 

ah, OK, thank you very much.
BTW, searching in the web, I found the module to use when you install a Third brake light. Here are the links, and one of my brake light.

Command Third Brake Light Logic Module
http://www.commandelectronics.com/logicmodule.html
http://www.buyautotruckaccessories.com/product.cfm/cf-bin/pn.pacer-taillight-logic-module/#apps

LED BRAKE LIGHT.
http://www.am-autoparts.com/AM/Tail-Lights/Chevrolet/Suburban/-/AM-18017556/?utm_medium=shoppingengine&utm_source=ShopzillaSF

 

UPDATE:
Well this weekend I put the relay and the third brake light worked fine. But after looking at the wire from the third brake light, I found that the wire had a little exposed part of the cooper material in the part between the camper shell and the tail door, so, now I understand why the third brake light shorted and blew the #13 fuse in the dash.
Now, my question is: do I let the relay there (with more connections, with the possibilty to fail)? or I reconnect the third brake light wire to the wire I found that comes on with the brake (only one direct connection)?

 

BUMP, BUMP

 

Since you found a short my vote is to reconnect the third brake light wire to the wire you found and give it a try. Less to go wrong.

 

yes, thank you, I was thinking the same thing. I will.