I've got a Mitsubishi Mr. Slim split ductless system in the "mother-in-law" suite of my house. There are 3 wall units connected to it, one in the front room, one in the bedroom, and one in the living room/office area. The bedroom one is set really low because that room is small, so the unit almost never has to come on.
Currently, the other two units are blowing air that's only semi-warm, and are not keeping their rooms up to temperature. Just a day ago they were able to do so easily. The outside temp has fallen somewhat, but the difference in internal temp seems excessive. I've noticed that there is ice on the bottom third of the cooling grid on the back of the external unit, and I'm wondering if this could be part of the problem. If I get that ice off of there am I likely to get any warm air back?
If so, since the grid is delicate, I'm thinking my best option to remove the ice is a heat gun on low, but I'm not sure what that will do to the cooling grid since it's that really light-weight, easily-damaged aluminum. Would I be okay using the heat gun?