I have a '93 Silverado that has 377,000 miles on it and I have put at least ten heater cores in the truck in the last three years or so. The manufacturer said I have something not ground that causes a stray electrical current, that causes electrolisis and the heater core failure. I have tried everything I know to find this current to no avail. I have remove all the fuses, checked with my digital voltage meter and I still have a current to the radiator. Has anyone gone through this and can help me???