Brakes Problem

[79 Seville]

My 79 Seville has a problem:

The calipers were recently replaced on the rear, but now the dash brakes light stays on, and the rears don't work like the fronts do. The Haynes manual doesn't give any help. I'm driving it like this, but need some insight on what could be wrong. Fluid stays up alright, no leaks seen. Any suggestions?

[CADIBROUGHAM]

If The Dash Brake Light Stays On Not The Abs Light But The Red Brake Light Stays On When Ever You Drive Then That Means A Couple Of Things. First Of All When Try To Reset Or Balance The Proportioning Valve. The Valve Proportions The Breaks
The Front Should Get 60 And The Back Forty. With The Car Off Take Your Foot And Stomp Of The Pedal Once Really Hard Give It A Good Kick. This Will Probably Reset The Light. If It Does Reset The Light And You Drive And The Light Come On Again Than You Know That Your Brakes Are Out Of Balance Or Their Is A Leak In The System. So If The Light Comes On Again Ckeck For Leaks If Their Is No Leaks In The System Than The Proportioning Vavle Is Faulty And Needs To Be Replaced. Once Replace The Brakes Should Feel Even And The Light Should Not Alluminate. Only By A Gm Proportioning Valve Do Not Buy Any After Market. Stick To Factory Parts When It Comes To Brakes.

Also When You Say The Rears Do Not Work Like The Front Do Do You Mean That When You Step On The Brake It Feels Like It Is Pulling You.?