I am getting a thick mold growth on one of my AC units within 4-5 months. Anybody else have this problem and found a solution?

What really puzzles me is why this unit and not the other 2 AC units that are in the same condo, although different rooms.

There is hardly any dust in the primary dust filter, so it is not a dust problem. The room is facing south and as a result, fairly dry with a relative humidity of 35-45%.

Because it hasn't been cleaned properly?

The AC unit is sized incorrectly, it is too large for the area it is cooling and is not removing enough moisture. The unit shuts down too early because it has reached the temp you are trying to achieve but did not dehumidify the room. if the unit is sized correctly check for proper drainage from the condensing unit. Look for the clear or white plastic drain line from the unit where the mold is.

Because it hasn't been cleaned properly?

+ 1, Ideally they should be cleaned monthly. A minimum cleaning period, would be 3 months.

I saw that white crap all over mine (filters) recently. Thought it was dust but so much it was amazing actually. So its mold is it?

We get it on our unit in the bedroom only. It's used every night, and mostly all night. It doesn't get as bad as yours, but we do get some mold. We clean it out every 3 months or so and have a pro come in and do it every year.

Drainage line works great. Very damp in the morning, so I know it's taking out the moisture. Being close to the sea might have an impact for us also.

Let's also try moving this over to the Housing forum.

Topic Moved.

It seems to me that once the mould is in place it is very difficult to get rid of it completely, and if you leave just a little bit it will come back quite quickly. Like fungal infections generally in fact.

So maybe the cleaning needs to be done with a power hose and bleach or something like that.

Gosh, what happen to TV? It look like it was hit by a virus or is using some stone age free software!

Anyway, you can use Caustic Soda (NaOH) to remove all mold on the AC fan.

Over-sizing is plausible, but I think the growth on bedroom ACs are due to the 12 hour on/off = wet/dry cycle. In a way the is good news as I was fearing the room was mold "infested".

A combination of two factors comes to mind. A room with high humidity (constant closed window or lack of a window?) and smoking in the room with the air con unit running. The vanes look like they are coated with a layer of tar.