Performed clean and check on gas furnace. Cleaned flame sensor and flushed drain line, inspected burner tubes, tested and inspected blower motor assembly and all electrical components, checked filter which does not need changed, tested t-stat operations and cycled system in low and high heat stages, conducted combustion analysis and measured temperature rise. System displayed code 9 (high heat pressure switch did not close or reopened). Inspected flu piping and combustion air supply for obstructions, inspected pressure switch tubing. Cleared clogged condensate trap which corrected the issue. Advised customer to call us if issue occurs again. Everything is operating normally at this time. Customer paid by check.