Red brake light on, front locks up ?

I have 88 Silverado RWD, red brake light on in dash, in winter front brakes lock up and slide easily. pretty scary! No fluid lose, new front pads, calipers, and slide bolts. The pedal seems a little soft until half way down then they lock up in front as soon as i feel some pressure. have not removed rear drums to inspect yet. Could this be caused by worn out rear linings or possibly a bad brake booster. any help would be appreciated.

Definitely check the rear brakes for wear and proper adjustment. Also make sure the parking brake is completely disengaged...there is no low fluid level sensor. Finally, if the fluid is old, dark, and green, flush it out with fresh fluid and make sure they are bled of any air...furthest wheel to closest to the master cylinder.

My guess is that the rear brakes were dragging and have become glazed...I like to use a 3M rust and paint stripping wheel attached to an electric drill to remove the glaze from the shoes as well as the drum surface, try to get a nice cross-hatch pattern. Hope this helps!

The red brake light in the dash being on, and the parking brake is off, usually means that the proportioning valve has sensed a leak in the front or rear system. When this happens the valve closes off the suspected leaking system (front or rear) and turns on the brake light.

Since you have front brakes, suspect the rears for leaks, or the rears are way out of adjustment, or a faulty proportioning valve.

Make sure the parking brake is not on (as said previously). Then pull the wire off the proportioning valve. If the light goes out, then there you have it.

I did notice the fluid is dark looking probably never changed, ill try that while checking rear linings and lines for leaks. Didnt think of the proportioning valve, ill try to disconnect that wire and see if light goes out. Also does anyone know how to read ABS codes with MIL after jumping the diagnostic Connector. Thanks for the Help