I have a model 50a50 241 White-Rogers control board that flashes 4 times, which on the control board says " open high limit switch". How do I do that or should I call a furnace repair person. I have checked online with White-Rogers and they only give info on their newer replacement versions of my model.
Getting cold... Please help

Check filter. If filter is plugged, it will cause limit to trip. Also, if you have central ac installed, and filter has been neglected for long periods, the evap coil may be clogged.

First change filter, see if unit will operate correctly. If not, replace high limit with factory recommended replacement. If you still have problems, call in the pros. Once problem is fixed, check filter once a month, change as neccisary. Biggest maintenance that can be done is keeping filters clean.