Here’s another photo from our residential estimator, Mike!  In this picture, you can see that the coils inside this homeowner’s A/C system are impacted and littered with possible fungal growth and dust. 

When you turn your A/C on, your system pushes the warm air over these coils.  The coils cool down the air, then the air continues down the line to exit out the vents in your home.  If your coils are this grimy, a couple things are possible:
1) The system has to work twice as hard to get air through.  All that dirt and debris means that your system is working overtime to push the air to the other side of the coils.
2) Possible odor issues and potentially hazardous microbes and fungal growth might be entering the air in your home.   
If you can smell a “musty” or “mildewy” odor whenever you turn on your air conditioning, it’s possible that you need to have your coils cleaned.  Call Power Vac America to speak with Mike and to get an estimate for cleaning your system!