740 GL Brake problem

Sound like the brake fluid in the reservoir sloshes away from the float during heavy braking. Check your brake fluid level, and if it's low, check your brake pads. Don't top it up unless all the pads are nearly new, or it will overflow when you push the caliper pistons back in when you do renew the pads. (Of course if the level is close to minimum or below, you should add some to bring the level up.)

Hi Mike.

There is no float in my reservoir tank, the fluid levels are O.K.

I notice sometimes that when the light comes on it can be at different intensities, from fully bright to just a dim glow which would lead me to think the problem may be more of a electrical problem as apposed to a real problem with the braking system.

Should the warning light just be on or of no dim or less bright

Les

Yes the light should be off or on, not dim. So you need to find the junction block where the balance switch is (follow the brake lines from the master cylinder), then trace that wire from the junction block back to the instrument cluster. (I assume your brakes are working normally?)