AC voltage gets mixed with DC
Get a Digital Multi Meter set to measure DC volts, check that you are getting 12 volts DC, then try switching the meter to AC.  If you see a Voltage there, then you have AC superimposed on your DC line.  Unshielded runs of cable can have AC induced onto them if they are near AC lines.  Also, poorly designed power supplies can cause this also.  Without knowing what device you are talking about, or how the ATS card is supplied, it is going to be hard to troubleshoot.  If things are failing, it could also be from over-voltage.  If the power supply IC is a linear and settable type, the components used to set the output could be out of spec and causing the regulator to provide more than the required 12v.  This could cause overheating and failure.  If the bypass caps on the regulator are missing it could send the regulator into oscillation which is also bad and can cause failure of ICs.