On arrival unit was off. Called for heat and unit began heating, after cycling off and back on, furnace flashed code for high limit switch. Limit switch is rated for 180, temp at limit was up to 192. Gas pressure is at proper range, filters are claen. Furnace ran longer with doors and closet door open. Recommend adding return to furnace to allow proper air supplied to furnace return. Also will need limit switch, due to number of times limit has opened.