Why does wall make ticking noise - Frigidaire FAC124 wall/Window Air Conditioner

Marvin, it could be water dripping into the drain pan under the unit or the metal of the outer shell is cooling off (metal stress). Also, is the drain pan is full the fan blades may be hitting the water, In which case the rear of the unit needs to be tilted down 1/4" to 1/2". So, the water will flow to the rear of the pan and out the drain hole.These sounds are normal and will do no harm. If you want to test this theory, turn the unit OFF & unplug it. If you still hear the ticking sound, it's one of the above.

Hope this helps & thanks for choosing FixYa.