Performed semiannual maintenance on one straight electric cooling system. Inspected all Performance, Mechanical and Safety Systems. Inspected the hot surface igniter for the heating system. Visual inspection revealed stress marks on the igniter. I did not visually see any cracks of the porcelain but electrically tested igniter and found it to be within the appropriate values recommended by the manufacturer. Flushed and treated the primary drain line. Left instructions with homeowner on how to properly flush drain line and ensure drain is clean and clear to help prevent blockages.