9 answers

HVAC Help!!! Terrible Smell Coming from HVAC Vents.

We have been in our house for 5 years. For the second year in a row we have had a terrible smell coming out of our vents. This only happens when the unit is completely off during the cool fall/spring months (same months last year, sept/oct/nov.) Last year we had our vents cleaned and checked for critters. We also had our attic space checked for any dead critters. We found nothing and after having the vents cleaned/vacuumed the smell was still there. The smell also seems to move from one side of the house to the other... my mother says this may be because of which way the wind is blowing. It also is stronger in the evening and not so bad/noticeable in the morning hours... my mother also says this could be caused by wind direction through the attic vent area. The smell does not continue once the unit is turned back on, once it gets too cold/hot. I don't know anything about HVAC but we have one unit outside and a unit in the attic above the garage (this is where we change the filters.) The smell is driving us crazy. We are going to call an HVAC company but we are afraid of getting scammed, being told that this or that will fix the smell, paying for it, then the smell comes back. We need someone honest and trustworthy. Someone who can give us a definitive answer or tell us if they cannot help. We have a Goodman unit and have heard they are notorious with issues but all of the research and info on the internet has nothing to do with a weird smell and are reports of bad compressors/wires/switches, ect. When we had our unit serviced last year they did suggest we have the "coils" removed and cleaned but could not guarantee this would take care of the smell. But that they had heard of this in trying to resolve issues with Goodman units in the past. Any advice, suggestions, knowledge about HVAC units and bad smell??? We don't want to throw a bunch of money out the window trying to figure out what is going on. TIA

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Thanks for all the advice and answers so far... Please keep them coming. Just some added info. We do not have a crawl space, we have a slab. So that rules out any mold issues, at least under the house. We have had the ducts cleaned, they also used a scoping camera (we have the flexible type ducts) to look in each of the ducts to check for rodents. We had a few guys crawl up into our attic space to look for any evidence of varmints on the outside of the duct work and they said it looked okay. We also had some "switches" replaced last year when the AC wouldn't kick on. At that time the smell was not an issue and the HVAC company said everything else looked fine. But again we weren't inspecting for a smell. I do have to say that the smell does not smell like mold. But we would not rule that out. I cannot explain the smell. Dirty, musty, rodent like... even though we were unable to find evidence of any. I am also confused... If something got in there and died wouldn't it stop stinking eventually. Especially after two years???
Also, someone had mentioned issues with the water heater causing an issue (the water heater being next to the HVAC unit, the problem being in the lines between the two.) Our water heater and HVAC units are not near each other. But I have no knowledge as to whether or not the two are connected??? Could the water heater be the issue?
Also, we are 99% sure the smell IS coming from the ducts. Just standing under them is enough. In the rooms where I keep the vents closed... no smell.

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Hi I have a guy that works on all my HVAC needs he may be able to help you. If you still need help email me Thanks S.

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It is prob not your HVAC system. We've had that same problem & it was mold under the house. You have to strip off any insulation that is under the house so it can breathe, and you need to get vent fans on one side only under the house (they sell those at Lowes, etc) to keep air flowing under there. Good luck!

What a terrible thing!

We've been very happy for many years dealing with Cool Ray. They babied our old systems along for several years before they finally gave up. We bought 2 new systems from them (upstairs and downstairs) and still use them for maintenance and service. We found them to be honest, trustworthy, on time. Highly recommend.

Sounds like dead critters.... not an actual HVAC issue? Have you had your home checked for rats? They are a very bad nuisnace in the Atlanta area... Seems if it was HVAC you would smell it when it runs..... You may have dead critters in your walls? Or under your house? (crawl space?) You may not smell it so much when the unit is on because the air is circulating.....

Make sure it is not mold. Check the crawl spaces and the basement and if you need to get air samples with mold plates. In the mean time I would sue air filters that have UV lights just in case. I have seen people in my practice get deathly ill from mold and other air born pathogens from their vents. good luck.

We had a similar problem, but we had a company called Daffy Ducts come out and take care of it. I worked with Jeff, I think he is the owner. They were very thorough, detailed and professional. I don't feel like they ripped me off and they did solve my problem. I would reccomend them.

Best of luck!

Hi I have a guy that works on all my HVAC needs he may be able to help you. If you still need help email me Thanks S.

Wet flexable duct work smells really bad. Like a dead fish. Do you have any roof leaks that might be getting the duct work wet? Any holes in the duct that might let hummid attic air in? Your A/C might be too small for your home, causing the A/C to reach its saturation point before the unit shuts down. In laymans terms, the A/C has removed as much moisture as it can but is still calling to run (thermostat still wants the A/C on), therefore condensation on the evap coil can not be removed causing moisture build up in the inside of the duct work. Do you ever have any moisture on you windows in the morning when the A/C is on? Bingo , theres your problem.

Hi, C.!
One of our close friends is a HVAC expert. Upon initial conversation, he's wondering if your insulation might be wet from humidity (during summer). If you have flexible duct work in the attic, then when you turn your heat on, it heats up, thus drying, the insulation can smell very bad (kind of like a can of bad tuna). Also, do you have any black spots on the vents in your ceiling?
Please contact him to discuss further. His name is Allen Loehr and can be reached at ###-###-#### after 3:00 ET or you can email him at ____@____.com.
Thanks so much! And good luck to you.

My husband put one of those Infrared things made just for ac's No more problems

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