my brake light on the dash comes on and it feels like there is no power boost while the light is on. it comes on and off radomly only at low idle like when its in gear (automatic) and you are not giving it any throttle. i unplugged the abs behind the glove box and nothing changed. I do have a redline vacum actuated trailer brake system on it that i have never used and no nothing about and the vacum pump was taken off the motor long ago. my truck is a 93' automatic 4x4 any ideas would be great! thanks

 

Booster maybe, leaking, or going through brake fluid

 

As Billy D said. You might also check your fluid level. And, when was the last time your fluid was changed?

 

its not low on fluid and i have never heard of anyone ever changing brake fluid?

 

You should change your brake fluid, it breaks down and collects moisture just like every other fluid in a vehicle. If your vacum pump is gone then your brake booster isn't working, unless you have hydroboost and I'm not sure if that was available on 1st gens.

 

the auxillary pump for the trailer brake system is gone. i took it off long ago since i put extra drag on the motor turning that extra pump and belt for no reason.

 

Brake fluid, unless it's synthetic, (which is crappy at best) is hygroscopic, meaning it absorbs moisture. If you open a container of fluid and leave it for a few days, you gotta throw it out, even with the lid on. Think of it like silica gel. Problem with this? The moisture will rust your brake lines, and well as being more compressable than the fluid is, giving you a squishy pedal.

 

That's good to know I will have to do that soon I'm sure its original fluid

 

Back to your origional question, if you have low vaccum it will light the brake light on the dash.There is a vaccum sender on the left fender well close to the master cylinder that is plumbed into the big vaccum line at the booster.Check your lines and booster for leaks. Possibly the pump is weak. They can be rebuilt the kit is readily available. Good luckRocky