The trade's shortcut is the age times cost rule: multiply the repair quote by the equipment's age. Under roughly 5,000, repair is usually sound. Over it, replacement usually wins. A $300 sensor repair on a 12 year old furnace (3,600) is a repair. A $1,500 blower and board on a 17 year old system (25,500) is money into a system whose other parts share its birthday.
Use the local version of the rule. Age in San Marcos is measured against a long cooling season and mild winters: compressors here accumulate summer hours faster than the national average household, so a 15 year inland system has done more cooling work than a 15 year coastal one. Weigh repair price against remaining life with that duty in mind, and let the 40 year outliers in this market stand as the warning they are: systems do not send a notice the season before they quit in a heat event.
Three facts adjust the arithmetic. Refrigerant: older cooling systems use refrigerants that now cost enough to make a major cooling repair a replacement argument by itself. Ducts: a replacement on failed ducts buys a new machine with the old complaint. History: a first major repair at 14 years is a different bet from a third at 14 years.
The output of a good visit is both prices in writing, with the duct findings attached. Companies earn the replacement by showing the repair price honestly first. If you are only shown one number, you were not given a decision; you were given a direction.
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