i have 1985 300sd with ABS.

i had an issue were my back brales were vibrating when braking down hill. The rotors wer cut and the pads were replaced, the issue did not go away. Just on a wim i was able to change my abs pump for a used one that i got for free. issue still did not go away. a month later my front brakes dragged pretty bad. I let them darg to long and my calipers seized. so.

In the past 2 months this what had been changed for new,

all brake hoses,
master cylinder
flushed and bled system.
all new rotors, and pads.

I have put on good used calipers today, put they still drag.

Does anyone think i should go back to my old ABS pump, since there was no issue with it before. Could an abs pump cause brake drag in the front?

Also, antilock light is on, but i'm 90% sure it's a charging issue. I had the light on gfor close to three months, and then i changed my battery, and it went out, but it came back on on a month later, figured my battery was not charging correctly....do you think my alternator could be causing my my brake problem?

am i missing something?

My car is not going to be drive until i get my drag issue resolved, i can't afford another caliper seize.