Strong Musty Garbage Odor When A/C Kicks On

[sarasota]

Hello all,

The other day, I turned on my central air for the first time in two months and I immediately noticed an overwhelming odor that smelled like musty garbage. I had been using my central heating for two months prior to this and never smelled this odor before. Nor did I smell it last summer when I was constantly running the a/c. When I have been running the heat or fan only, I do not smell the odor. It only starts when the a/c is switched on. I live in the Florida area.

I had a tech check the evaporator coils and from the front view, they appeared clean and mold/gunk-free. The drip pan was dry but he did notice a generous collection of an oily type substance in the corner of the pan. He said it had an odd smell and then cleaned it up. He checked the attic for the odor I had described and carefully inspected the duct work. He didn't find anything unusual and suggested that maybe I should get the ducts cleaned...

The A/C unit is about 7 years old and in excellent shape I've been told. The coils have some rust on them however. The A/C system is very efficient so I do not believe that I have a Freon leak. I also have the unit maintained regularly. Because the odor is not present when the fan only or heat have been running, I don't believe that it is a problem with mold or dust in the ducts. The air handler is located in the garage. The garage area is odor-free. The A/C filter is replaced regularly. I had the attic inspected for rodents by a professional and nothing was found.

So, I am at a complete loss. Other than having the evaporator coil unit pulled and cleaned, does anyone have any other theories on what might be going on here? I am scared to use the A/C now...

Thank you so much!

Stinky in Sarasota

[paul52446m]

Hello all,

The other day, I turned on my central air for the first time in two months and I immediately noticed an overwhelming odor that smelled like musty garbage. I had been using my central heating for two months prior to this and never smelled this odor before. Nor did I smell it last summer when I was constantly running the a/c. When I have been running the heat or fan only, I do not smell the odor. It only starts when the a/c is switched on. I live in the Florida area.

I had a tech check the evaporator coils and from the front view, they appeared clean and mold/gunk-free. The drip pan was dry but he did notice a generous collection of an oily type substance in the corner of the pan. He said it had an odd smell and then cleaned it up. He checked the attic for the odor I had described and carefully inspected the duct work. He didn't find anything unusual and suggested that maybe I should get the ducts cleaned...

The A/C unit is about 7 years old and in excellent shape I've been told. The coils have some rust on them however. The A/C system is very efficient so I do not believe that I have a Freon leak. I also have the unit maintained regularly. Because the odor is not present when the fan only or heat have been running, I don't believe that it is a problem with mold or dust in the ducts. The air handler is located in the garage. The garage area is odor-free. The A/C filter is replaced regularly. I had the attic inspected for rodents by a professional and nothing was found.

So, I am at a complete loss. Other than having the evaporator coil unit pulled and cleaned, does anyone have any other theories on what might be going on here? I am scared to use the A/C now...

Thank you so much!

Stinky in Sarasota

The compressor has oil in it and a small amount of this oil migrates through the system with the freon. So if you had oil in the coil pan, i would think you
have to have a small leak in the coil. Maybe you have not lost enough to bother your coiling as yet, but that is the only place that oil could be coming
from. Later Paul

[sarasota]

Problem Solved!

Had a technician come out from another company to diagnose the problem. After checking everything, he was 99% convinced that the foul odor when running the a/c was due to a microscopic mold build-up on the evap coils (invisible to the human eye). Although the the coils appeared clean, there was likely something going on behind the scenes. No leaks were detected in the coils which was great news. The tech thoroughly cleaned and then sanitized the coils with a special chemical which kills mold and bacteria and flushed the drain pipe. I also purchased and installed a brand new filter in case some mold spores were hanging around on the old one.

Finally, I tested the a/c and magically, the foul order had disappeared and has not returned since.

[sarasota]

Bad News...

Unfortunately, the musty smell is back after only one month... I am at a loss. Other than getting the coils cleaned every month which can get costly, I'm not sure what else to do other than have a UV light installed which I am somewhat against doing. Any ideas?

[gabagoo]

Our central air also has a foul cheesy smell when it first starts up, but goes away rather quickly.

[sarasota]

Well, we had the coils cleaned again and a sanitizing UV light installed. So far, no problems. The smell usually starts when we are switching between the heat and the a/c. Hopefully, this will solve the problem! At least your smell goes away after a while!