Thought I'd post on a new thread to help anyone with similar problem. Hopefully this would be easier to find.

You may want to read the entire thread at:

Looking for rebuilt power brake booster

Vehicle: 1992 Vanden Plas

Affected models: 1990 through 1994 XJ40

Problem: Intermittent, random, red "Brake" light going on and off. Amber "Anti-Lock" light also lights up randomly. This may occur when applying brakes or just cruising down the highway. The main brake pump fuse (30 amps) was also being blown at random. Loss of power assist to brakes when fuse is blown and accumulator is depleted.

Cause: The hydraulic pump relay was faulty. Cost, approximately $50.

Hope this helps someone.