Mildew smell from heat pump?

[mincus]

Hi all,

I've had a heat pump for the last 10 years, but lately I'm getting a bit of a mildew smell coming out of the ducts. It doesn't happen all the time, but it's definitely noticable when it does. Is this related in any way to the operation of the heat pump? Or is it mold/mildew growing in the ducts?

I pulled the front panel and looked at the A coil and it's pretty clean.

My first thought is to clean the coil with some of that foaming cleaner and see if that works.

Anyone have thoughts on adding a UV light to the system? Do those really do much and are they worth it? A couple of us have semi-severe allergies, and one has asthma. Looking to make sure the air is as clean as possible.

Thanks all!