Arrived to find the the limit switch by the blower motor had tripped on amana unit located in garage. Reset switch and unit is now running. Adjusted outlet gas pressure from 3.8 down to 3.2 in wg. Cleaned rusty burners and flame sensor. Unit was still tripping out on high limit. Checked evaporator coil and it is very dirty and in rough shape. Switched dipswitch for 2nd stage delay from auto to 5 mins. Adjusted gas pressure down to 1.7 in wg. Unit is operating for now. Ed is on his way out to give an estimate for a new unit.