making the switch isnt the problem, its installing it correctly, if you do it wrong the led wont light up at all, or will stay on all the time. i could give u step by step instructions but when i did this i insatalled it on a ford focus, and then i also did it to a mazda 626, i could figure out how to put it in a tC, but it would take me a little while to write up a wiring diagram that would make any average person be able to install it correctly
send me a message on my companys myspace and ill get back to u when i get a chance to look at the wiring diagram for tha tC

 

www.myspace.com/exoticaznautoz

 

i dont have a myspace.

 

humm, i really dont wanna give out my email on here, here, email this sn and ill send u an email back witht he address i use for the company, LuZooM1569@yahoo.com