Air Brake Antilock Control Unit/module problems of the 2000 Chevrolet Astro

I have a 4 year old chevy Astro van with a kelsey hayes ebc unit. Recently the abs light started coming on from time to time when the engine had been running for a while, but it would go off when the vehicle was turned off and restarted cold. I had my brake system checked and there was nothing wrong with the brakes. The code indicated a bad relay in the computer control system. The problem is that it causes the abs light to come on and when that happens I have no abs working. This could cause a safety issue under certain braking conditions. The light doesn't come on all the time so the question is do I pay $800 for something that I believe to be a manufacturing defect or do I take a chance that when I need my brakes that the abs system will work. As of now, I have not replaced the part. The dealer indicated that the part # was 13354733 he could not/would not tell me the type of kelsey hayes ebc unit except he said they only made one kind for this vehicle.