What is the most common cause for an old air conditioner to lose effectiveness?

And what can be done to improve it? How much will it cost?

Answers:
Best you call a Service Tech- one who won't lie if you can find one- Clean the Coil inside the furnace and the coil on the Condenser unit- add freon- Cleaning the unit will usually make a 20% gain in performance, you can do it your self- buy Coil Cleaner at Home Dep.

Other answers:
freeon just find a cheap cooling repair and tell them you think your old ac is out of freeon and if they could come and service it
freeon just find a cheap cooling repair and tell them you think your old ac is out of freeon and if they could come and service it
first it probably needs to be cleaned and second it may need freeon or coolant added to it. You just have to call someone that deals with air conditioners to find out the cost.
If it still blows like before but is just not cold anymore then Freon has probably leaked out. Refill it but check for leaks.
If it is a window unit, dirty coils will cause that. Pull it out and hose out the coils. If it a central unit, a plugged filter, bad blower motor, or low on refrigerant will cause that.
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