Got a 89 S10 Blazer 4wd a few months ago. It hadn't run for a few years and I have slowly been working through the issues. Most frustrating issue is the Brake Warning Light. Won't go out. Does dim when the parking brake is released. When I got the Blazer, first time I pumped the brakes, I blew out one of the rear lines. As a line got replaced, another would blow until I replaced about 5 of the lines. I also replaced the rear drum brakes including the wheel cylinders, since I thought I was seeing some leaking brake fluid from one of them. Bled the brakes several times and I am getting fluid out of both the back and front bleeders, so I don't think the proportioning valve is stuck one way or the other. Fluid level has been checked and topped off (essentially completely flushed by the repeated line replacements). I checked the parking brake switch and the warning light does dim slightly when you release the parking brake. I disconnected the proportioning valve sensor and the light stayed on. I disconnected the ABS module and the proportioning valve sensor and the light went out. Reconnected the proportioning valve sensor and the light came back on. Did not matter whether the ABS was connected or not, now the light won't go out again. Not sure where else to go at this point. Starting to sound like an electrical issue to me (bad ground maybe???). Anyone have similar experience and know how to fix this problem? Need to deal with this so I can get the thing inspected and put it on the road. Thanks in advance.

 

make sure the float in the fluid reservoir is working properly, like it floated all the way to to the top. if not tray tapping it with a small hammer.

if your confident your brakes are working good like they should and all the rusty brake lines are replaced start it up and stop on the brake pedal, sometimes thats enough to reverse the switch inside the proportioning valve. i worked on a old astro fan with the same issue and tried everything to get that light off finally i got pissed off and jumped on the brake pedal and the light went off