I have a old Chrysler airtemp furnace a/c unit model 4213-04 with a digital thermostat. When I turned on the a/c I got nothing. I'm getting 1.2 volts on secondary at transformer and less at limit switch. Is the black box (Honeywell r8226a 1057 1) a switching relay and could this be why the a/c does not switch on. I have no voltage to the fan motor and the batteries in the thermostat have been replaced.