94 Brake System Warning light - ?

Hello,

I am new to the group - looks like there are a lot of knowledgable people here!

I have a 94 Surburban. A month or so ago the ABS light came on. I could live with that. Figured I would get it checked at the next service. It is intermittent.

Friday, the Brake System warning light came on as well - the light came on at exactly the same time as the ABS light - when I "got up to speed" - about 40 mph. When I stopped, both lights went out. This was repeated when I turned around to head home. The pedal did not seem like it was giving and it seemed like I had normal brake pressure.

Still, I didn't want to take chances and took to my mechanic. He says the hydraulics are fine, the brake hardware is "perfect" and that the car is safe. The fluids are fine and I have a good vacuum. He said I would have to take it to the dealer to get them to diagnose it. He says I should drive it until the light comes on for good. He is convinced it is an electrical problem - perhaps a bad sensor or wiring.

I called the dealer and they said that they couldn't computer-diagnose it unless the brake system light stays on. They said I should bring it in for them to look at, but basically I would only do that if they could get a code. My mechanic is pretty good and he already checked the system.

I guess it could only be a few things:
The master cylinder
The brake fluid
The vacuum brake booster
Bad sensor / wiring

It is really intermittent. Drove it today and the Brake System light didn't come on at all [although the ABS light did].

I don't want to take it in to the dealer and pay $135 to hear them say they need to have the light on constantly or to try to fix the ABS problem and then have the same brake system problem.

I want to get the brakes checked and fixed. I really want to make sure it is safe for me, my family, and those around me.

Any suggestions / ideas / feedback? Is it safe to drive until the light comes on for good?

Thanks