Indicator Module

I have an exp bus and Indicator Module installed on my RV-6. They've worked fine for the last 12 years with one exception. My indicator module indicates 20 amp drain continuously when the power is on. My null adjustment screw doesn?t seem to have any effect. Is there anything I can do to correct this? Is there a way I can get it repaired if necessary? Is it worth the cost? So far no response from Control Vision.