99 blazer rear discs not applying

Initially had lots of air in the rear lines and abs unit but got it all out and now have a great pedal. Neither the red brake/park light nor the amber abs lights are on. Problem is no rear brakes.

I bled them using the pedal so they are definitely getting fluid into the calipers but can't figure out what else to look for. Also had one caliper off to remove and replace snapped off bleeder and while off was able to easily depress the piston into the caliper. Only did it about an eighth of an inch. The piston did push back out and up to the pads after I bled the brakes.

I lifted the rear end and ran the truck but no matter how gentle or how hard I pushed the pedal the rear wheels kept spinning. Note pedal felt good. Also tried stopping on iced up street with abs unit disconnected and although fronts would lock up the backs kept turning.

Help!!!!

If air has got into the ABS unit bleeding brakes requires a ABS capable scanner.

How did you get air into it to start with?

Air must have got in there when the line running along the frame to the rear rusted out. I believe the mc must have leaked dry as truck sat and fluid dripped from rusted line. It sat for quite a while before we replaced the line. After replacing the line and bleeding the pedal was spongy but I didn't notice the pedal travel was excessive til we hit 40 below. Was then that I realized there was a lot of air trapped inside.

Have it pressure bleed and put on a ABS capable scanner and do the ABS bleed procedure in the sanner.
Let us know how it goes.

Will do and will let you know the results. Thanks