Performed ac diagnostic split system attic and back yard. Found upstairs tstat not working. Went into attic 2 furnaces and coils in attic, found that unit had power high voltage and low voltage, just not sending power back to control board, removed control board from unit to inspect back of board. Found that board has what appears to be a burnt connection on the molex plug that supplies low voltage/ control voltage. No led indicator light. Paid 100 dollar deposit, owes 700 at time of installation of control board. Will contact tomorrow morning with availability of part and eta for install, upstairs without air conditioning.