I had some troble with my tail light took it to a shop.Now when I put on the brake the lite dims.

 

both of them or just one?

 

I got that fixed,wiring,.anyway I had to take off the rear wheel to get to the wiring.I pressed the rear brake to check the lite.forgot i had the rear wheel off.Now i can not get the caliber to open back up??

 

unless these guys know a secret squirrel trick, you're gonna have to crack open the rear brake master cyllinder, then GENTLY spread the pads apart.

 

Just take a paint scraper or screw driver and put between pads and lever both ways toward pistons. Since you are not replacing with newer thicker pads there should be room for fluid in master cylinder to go. Why were your lights dimming?

 

Yes, pry the pads apart, USE SOMETHING CLEAN, and wide so that you don't gouge the pads.If you cannot easily do this, loosen the bleeder screw and the pads will move easily.

Don't let the expelled brake fluid get on any painted surfaces, it eats paint.
You may have to bleed the brakes afterward, but if you open the bleeder and slowly push the pads and have someone else close the bleeder while you are still pushing the pads you might prevent air from getting in ( positive fluid pressure)

MK