I have a comfort aire pac-121 and the display is reading e4 and the ac is not working. i can't find a manual on line. How can I fix the problem? thanks andy

I have the same model, though several years old, and on mine E4 simply means the reservoir is full. Try emptying the reservoir tank and then turning the power on again. If the drain hose outlet isn't angled down, the water drains into the tank, which will need to be emptied regularly. (For constant use, may need to be emptied several times a day.)