AC Repair Cost: The Most Common Problems, Ranked
Jay Lelyukh, a former HVAC technician, went back through a full year of his own service call records, 242 AC repair visits in all, and ranked what broke, from most common to least. This is not a generic list of possible problems. It is frequency data from real jobs.
Most “common AC problems” articles are written from general knowledge of what can go wrong. Because this one is built from an actual service log, it shows what is likely to fail, not just what could. For how central air compares with every other heating and cooling option, see our complete guide to home HVAC systems.
If your AC just needs regular upkeep rather than a repair, the guide to central AC maintenance covers what a maintenance visit involves. If repair costs are starting to approach the price of a new system, the guide to central air conditioner installation cost covers replacement.
Have a heat pump rather than a central AC? Its outdoor unit shares many of the same parts, and the guide to heat pump repair cost covers the failures specific to heat pumps.
The #1 Cause: A Failed Capacitor and What Replacement Costs
Out of 242 calls, 52 were a bad capacitor inside the condenser unit, by far the largest single category. A failing capacitor often bulges visibly on top, and occasionally the top pops off entirely, spraying dielectric grease across the electrical compartment.
A capacitor can also look normal and still be bad, which is why technicians check it with a meter or simply replace it, since it is the most common fix. AC capacitor replacement typically costs $150 to $400.
Capacitors fail with normal age, but a dirty condenser coil or a dirty furnace filter speeds that up, and a cluster of capacitor failures reliably follows a major thunderstorm.
The #2 Cause: Low Refrigerant, Which Always Means a Leak
A central AC is a permanently sealed refrigerant system. Unlike a car that needs gasoline, the refrigerant charged at installation is meant to stay in the system for the unit’s entire life.
If refrigerant is low, a leak exists somewhere: in the outdoor unit, in the indoor coil on top of the furnace, or along the line set between them, usually at a brazed joint.
About 80% of these leaks are in the indoor coil, and that leak usually can’t be spot-repaired. The solder joints inside the coil sit so close together that heating one to fix a leak often opens a new leak in the joint next to it.
The replacement coil itself runs $600 to $1,000 for the part alone. Installed, with labor and trip fees, a coil replacement typically totals $1,200 to $2,500 or more. That is why many homeowners choose to refill the refrigerant every year instead, knowing a refill is temporary: the pressurized system slowly leaks back out, even over a winter when it isn’t running.
The Ice-Covered Coil: One Symptom, Many Possible Causes
A frozen indoor coil is one of the most common symptoms in AC troubleshooting, and several very different problems produce the same visible result:
Low refrigerant: reduced pressure drops the coil’s temperature below what the system was designed for.
Too little airflow: a bad control board that isn’t powering the blower, a burnt-out blower motor, or a very dirty filter means not enough warm air crosses the coil to keep it above freezing.
Whatever the cause, the way to thaw the coil is the same:
Turn the AC off at the thermostat.
Switch the fan from “auto” to “on” so it keeps running and melts the ice.
Expect a lot of water to run down the furnace as the ice melts, so put down towels and move nearby boxes and carpet first.
Thawing only clears the symptom. A technician still needs to find which of these causes froze the coil, or it will freeze again.
Motors, Compressors, and the Point Where Repair Stops Making Sense
Several of the most common failures involve motors and compressors, and these are where the repair-versus-replace conversation gets serious.
Condenser Fan Motor
A burnt-out condenser fan motor shows up as the compressor running while the fan stays still. The compressor overheats and often trips the breaker, and the fan blade is usually seized rather than spinning freely.
Oiling a seized motor rarely holds for more than a week or two, so replacement is the real fix. The capacitor is typically replaced at the same time as routine practice.
Blower Motor
A burnt-out blower motor inside the furnace often announces itself with a burnt electrical smell and a seized blower wheel. Sometimes the motor just hums weakly, which usually means its own capacitor has failed rather than the motor itself.
A motor that has been straining against a dead capacitor often doesn’t have much life left either, so the two are frequently replaced together.
Compressor Problems
Compressor failures are the most expensive repairs on this list, and they come in three forms:
Shorted to ground: the breaker trips immediately every time it is reset. The technician checks the compressor’s internal windings against its casing; if a short is confirmed, the compressor has failed.
Locked rotor: the fan runs and everything else comes on, but the compressor only hums every 20 seconds without starting, drawing too much startup current. A hard start kit sometimes frees it by cutting startup amperage roughly in half. If that doesn’t work, the compressor is locked up and needs replacement.
Worn out: refrigerant gauges show the compressor isn’t pumping properly because its internal valves have weakened. There is no fix beyond replacement.
A failed compressor is expensive enough that many homeowners choose a full system replacement over a compressor swap, especially on an older unit. Our guide to AC compressor replacement cost breaks down that decision.
Simpler, Cheaper Fixes: Filters, Drains, Breakers, and Wires
Not every common problem is expensive. These are usually quick, low-cost repairs:
Plugged condensate drain: water leaks around the furnace even while the AC cools the house fine. The drain fitting itself is usually clogged rather than the hose, and clearing it is straightforward.
Neglected furnace filter: a filter left unchanged for a year or more can restrict airflow enough to freeze the coil, just like a mechanical airflow problem.
Tripped breaker: a single trip is often just a nuisance. A breaker that trips again immediately after being reset points to a short worth investigating.
Broken wire connectors: worn loose over time by the unit’s constant vibration, and simple and inexpensive to fix once found.
Filters are directional, with an arrow that should point toward the furnace. A medium-grade pleated filter is generally the right balance: ultra-dense premium filters can restrict airflow too much, and basic fiberglass filters let too much through.
Less Common Problems Worth Knowing About
A handful of rarer issues round out the picture. None are common, but each is worth recognizing if your system’s symptoms don’t match the typical failures above:
Leaking coil drain pan: often welded to the coil, so it usually means a full coil replacement rather than a standalone repair.
Mice in the electrical compartment: nests can do memorable damage to the wiring.
Restricted metering device: a blocked piston or TXV, which takes specialized refrigerant gauges to diagnose.
Vandalism: from a punctured refrigerant line to deliberately cut wiring.
What Central AC Repair Typically Costs
AC repair costs vary widely with the specific failure, from simple, inexpensive fixes to repairs approaching the cost of a partial system replacement.
Common Repair | Typical Cost |
|---|
Capacitor replacement | $150 – $400 |
Contactor replacement | $150 – $400 |
Condensate drain clearing | $100 – $250 |
Control board replacement | $300 – $800 |
Condenser fan motor replacement | $300 – $650 |
Blower motor replacement | $300 – $700 |
Refrigerant leak repair (indoor coil replacement, installed) | $1,200 – $2,500+ |
Compressor replacement | $1,500 – $3,000+ |
Emergency or after-hours calls typically add a premium over standard scheduling. That is one more reason to deal with a developing problem, like a nuisance breaker trip or a weakening capacitor, before it becomes a full breakdown.
What to Look for When Hiring an AC Repair Technician
A specific diagnosis, not just a symptom. A technician who names the failed part (a capacitor, a specific relay, a particular joint in the coil) is giving you information rather than a guess.
Where the leak is. If a refrigerant leak is diagnosed, ask whether it is in the indoor coil, where most leaks occur and spot repairs are least likely to hold. That decides whether yearly refills or a new coil makes more sense.
Whether replacement was considered. For a compressor diagnosis (shorted, locked, or worn out), ask whether a full system replacement was weighed as an alternative, since the costs can be close.
The right filter grade. Ask what filter your system needs, since an overly restrictive filter can cause the same airflow problems that freeze the coil.
Final Thoughts
AC failures aren’t evenly spread. A small handful, led by a bad capacitor and low refrigerant from a leak, account for a large share of service calls. Knowing that a frozen coil can have several causes, and that some repairs (a failed compressor, a leaking indoor coil) start to rival replacement cost, helps set realistic expectations before a technician arrives.
If your AC needs a repair you’d like priced by more than one company, Home Services Pros connects homeowners with licensed HVAC technicians in their area for free, no-obligation estimates. Or call (833) 586-2038.
Frequently Asked Questions
What is the most common cause of AC problems?
Based on real service call data, a bad capacitor is the most common AC repair, followed by low refrigerant from a leak. Capacitors fail with age, faster with a dirty condenser coil or filter, while refrigerant loss always means a leak somewhere in the sealed system.
How much does it cost to replace an AC capacitor?
AC capacitor replacement typically costs $150 to $400. It is the single most common AC repair, and technicians often replace the capacitor at the same time as a condenser fan motor.
Why does my AC coil keep freezing up?
A frozen coil can come from low refrigerant, restricted airflow from a dirty filter, or a failed blower motor or control board that stops air from crossing the coil. Finding the actual cause takes a real diagnosis, not just thawing the ice and hoping it doesn’t return.
How much does it cost to fix a refrigerant leak?
About 80% of refrigerant leaks are in the indoor coil, which usually can’t be spot-repaired, so a coil replacement often costs $1,200 to $2,500 or more installed. Many homeowners instead refill refrigerant yearly for a few hundred dollars, knowing it is a temporary fix.
Is it worth repairing a compressor or should I replace the whole unit?
Compressor replacement often costs $1,500 to $3,000 or more, which makes a full system replacement cost-competitive. That is why many homeowners replace the whole unit once a compressor fails, particularly on an older system.
What is the best type of air filter for a central AC system?
A medium-grade pleated filter offers the best balance for most systems. Ultra-dense premium filters can restrict airflow enough to contribute to coil freezing, while basic fiberglass filters let too much debris through.
How do I know if my AC breaker trip is serious?
A breaker that trips once and then runs fine after a reset is usually a nuisance trip. One that trips again immediately after being reset indicates an electrical short that needs to be diagnosed, not reset repeatedly.
