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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
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Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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I have an older AC unit, more than 20 years. Is it possible

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I have an older AC unit, more than 20 years. Is it possible for a unit of that age to be low on freon without actually having a leak? I have lived in this house since 1996 and there has never been any freon added, though I have had to replace the capacitor and the contacter.
JA: Did you double-check the thermostat? And what about the unit's filters?
Customer: Thermostat seems to be OK, it is an old mercury switch type. Filter at return air looks good, secondary filter is not clogged
JA: Do you plan on doing the work yourself?
Customer: If I possibly can. I am only part time employed and not making ends meet as it is.
JA: Anything else we should know to help you best?
Customer: When the unit was running early this morning, after I replace the capacitor, it was putting out 57 degree air. As the outside temp began to rise, the compressor stopped coming on though the inside blower fan was running. It had cycled several times previously and each time the temp would drop to 57. I have had it shut down now for about 1/2 hour.

Hi I'm Brian and I'll be happy to help you figure this out!

On the first question: It's not possible for a unit to be low on refrigerant unless some has leaked out or been taken out. Refrigerant is not consumed in any way shape or form in an ac unit.

With that said, it sounds like you have a different problem although you should have the refrigerant level checked. With a system of that age, the first thing I would do is look carefully at and thoroughly clean both the evaporator (cooling) coil and the outdoor unit coil (condenser coil). I would also check the indoor blower wheel and housing for accumulated dust and dirt and clean if necessary. Then after the outdoor coil dried, I would check the refrigerant level.

With a leaving temperature so low on a warm start up, this really points more toward a clogged (dirty) evaporator coil (indoor coil) or a dirty blower wheel. Either of these conditions cause low airflow and low supply air temperature. It can also cause ice-ups. You can't really tell if your refrigerant level is correct unless both coils and the blower wheel are clean/cleaned.

Let me know if you have questions about this.

Thanks,

Brian

Customer: replied 2 months ago.
The unit itself was put in the house to replace the original closet style furnace from the 1950's. I have taken the covers off the interior unit but do not see the actual coil. The system is a Lennox installed in 1991 (found a date). Is the coil above the furnace in a system like this? If so it is completely wrapped in insulation and not visible at all.
Customer: replied 2 months ago.
Additional note regarding the temperature. I have a thermometer in the vent in one room, it starts out at 80 plus and comes down to the 57 degree level over two or three minutes.
Customer: replied 2 months ago.
Hello?

Ok thanks for the added info. If you still have a gas furnace then yes, the cooling coil would be above the gas furnace and many times they are insulated on the exterior. Newer coils for gas furnaces are encased in a factory sheet metal enclosure and insulated on the inside of the enclosure but many older ones were insulated on the exterior. That's unfortunate you can't gain access to the cooling coil, chances are after 16 years it has accumulated a lot of dust and is likely pretty dirty. A qualified and quality technician should be able to gain access to it to check it/clean it.

Yeah, with that temperature coming out of the vent, I would bet you don't have proper airflow for one of the reasons above. It sounds like your furnace and cooling coil need a really thorough cleaning! Then the refrigerant level can be checked and perhaps it may be a little low. Tiny leaks at gauge port caps are common so it could be slightly low on refrigerant as well as in need of cleaning.

Sorry, I"m not a very fast typist ;)

Customer: replied 2 months ago.
Okay, thanks. That gives me something to go on at least. I'll start by cutting power to the whole thing and get a vacuum after it and the internal filter housing as well. If that doesn't do it, I guess I will just have to add more debt to my credit card.I appreciate your help.

You're very welcome! I hope the best for your situation. Thanks for allowing me to help and for using Just Answer. Please remember to rate you interaction with me before leaving, that's how I get credit for working with you.

Best regards,

Brian

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