Upon arrival customer stated that home is for sale and that when they had the inspection done the inspector mentioned that the heat was not working. At that time customer stated that gas was not turned on to the home and that they did have it turned back on. Did full evaluation of both heat and ac unit which are 18 years old. Checked over all operations in attic at gas furnace, prior to turning the system on found that heat was not coming on due to air being in gas line, bled line, gas came through and was able to test system restarted system and everything came on. When unit starts up in heat mode the inducer draft motor is very loud and pulling high amps. Flame sensor is dirty and needs to be cleaned. Blower wheel is very dirty and blower motor capacitor is testing bad. Changed (16x25x1) system filter. All duct work and supply/return plenum were in good shape. Heat does come on and work. Performed combustion analyzer test and found no issues with heat exchanger. Checked over all oper