What can cause repeated failure of ac controller on a 97 suburban?

customer states it fails only on engine start up. once new controller is installed , it takes a week or 2 to fail.What can cause repeated failure of ac controller on a 97 suburban?
Like Frank said - I would check ALL the ';Body'; - ';Chassie'; %26amp; ';';Frame to body';'; %26amp; Engine to Frame grounds.What can cause repeated failure of ac controller on a 97 suburban?
sounds like its using the ac circuit as an earth for the starter.check all earth to chassis and chassis to engine wires.