Oily smell from gas furnace/AC


Late last August we noticed an oily smell coming from the central AC. It is even worse now that heating is on. The furnace is gas, high efficiency, and was checked by a furnace repair person. The CO emitted is zero, so I don't think the smell is the result of a cracked heat exchanger. Any ideas.
Thanks, Dave
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Dave Boland wrote:

Hi, Blower motor has capacitor which has oil in it, may be it is leaking(going bad)?
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How long did you run the AC after you noticed it?? I mean, was it late season for you and you have'nt used it much since?? I would have it checked for a Freon (refrigerant) leak. If the liquid line was leaking at (or near) the metering device in the evaporator, it would do exactly like you have described, and could continue for quite some time even after it runs out of refrigerant. You may even notice some oiliness (or dust sticking) at the evaporator where the smaller of the two refrigerant lines enters. Some people don't realize this, but some of the oil from the compressor will circulate with the refrigerant in an AC system, and leaks on the liquid side tend to show a lot more oil than leaks on the vapor side. There are other possibilities as well, such as motor going bad, spills into duct boots or top of furnace, furnace blower eating pieces of a badly clogged filter, etc.
HTH, Lefty
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Lefty wrote:

Thanks Lefty and Tony,
We noticed the smell late August. No problem before that time. The performance of the AC system seemed ok, so I didn't suspect it. The problem is continuing into the heating season. I made arrangement for a factory trained person to stop in and I will mention everything the tow of you have suggested. Thanks again!
Dave,
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Maybe you are smelling mold
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A cracked heat exchange will not give you an oily smell when the AC is on. Given that it is gas, it probably won't even when the heat is running.
Could be a lot of things, like an over lubed dripping motor, mold in the condensate pan, dirty coils. Get a pro to check it out and clean everything, especially the coils.
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