Your air conditioner just quit on the hottest afternoon of the year, and the house is already climbing past 80°F. Before you pay a $75–$150 diagnostic fee, here is the honest verdict: most AC repair calls turn out to be one of eight simple problems — a tripped breaker, a clogged filter, a dead capacitor, or a blocked condensate drain — and every one takes under 30 minutes to check yourself.
Work through the checks in order, and you will either fix it free or walk into the pro visit knowing exactly what is wrong and what it should cost.
Table of Contents
Start With the Symptom, Not the Toolbox
Good AC repair is diagnosis first and parts second — swapping parts at random is how a $25 capacitor turns into a $400 bill. Find your symptom below, then jump to the matching check.
| Symptom | Likely cause | First fix | DIY or pro? | Cost |
|---|---|---|---|---|
| Nothing happens | Tripped breaker, thermostat off | Checks 1–2 | DIY | $0 |
| Hums, fan won’t spin | Dead capacitor | Check 5 | DIY part | $15–$40 / $150–$400 fitted |
| Runs all day, barely cools | Dirty filter/coils, low refrigerant | Checks 3, 4, 7 | DIY, then pro | $0–$40 DIY |
| Ice on coil or lines | Restricted airflow, low refrigerant | Check 3, shut off | DIY, then pro | $0 / $200–$600 |
| Water by indoor unit | Clogged condensate drain | Check 6 | DIY | $0–$20 |
| Short cycles | Dirty coil, low refrigerant | Checks 3–4 | DIY first | $0–$150 |
| Warm air from vents | Thermostat, frozen coil, compressor | Checks 1, 3 | DIY first | $0–$400 |
| Burning smell, grinding | Failing motor, electrical fault | Stop — call a pro | Pro only | $300–$700+ |
The 8 Checks to Run Before You Call for AC Repair
Work through these in order. Most homeowners find the problem by check 4, and each takes five minutes or less.
1. Check the thermostat — really check it
Set it to COOL, at least 5 degrees below room temperature, with the fan on AUTO, not ON. A thermostat left on HEAT, a dead battery, or a fan stuck on ON (blowing room-temperature air between cycles) causes a surprising share of AC repair calls. Blank display? Swap the batteries first.
2. Check the breaker and the outdoor disconnect
Find the double-pole breaker labeled AC or condenser in your electrical panel. If it is tripped, flip it fully OFF, then back ON. Then check the grey disconnect box beside the outdoor unit — its pull-out switch can get bumped or corroded, and a loose pull-out reads exactly like a dead unit. If the breaker trips again the moment you reset it, stop: that means a short or a seized compressor.
3. Check the air filter — the number-one cause of weak cooling
Pull the filter out and hold it up to a light. If you cannot see light through it, it is choking the system: restricted airflow drops the evaporator coil below freezing, ice builds up, and cooling collapses — which is why a dirty filter is the first thing any AC repair technician checks. Replace a 1-inch filter every 1–3 months. Found ice? Turn the system OFF, run the fan alone to thaw it (see our guide to a frozen evaporator coil), and if ice returns within a day, call a licensed technician — that means low refrigerant.
4. Clean around the outdoor condenser
The outdoor unit needs two feet of clear space on every side and a clean coil to dump heat. Shut the power off at the disconnect, clear leaves and grass from the fins, and rinse the coil gently from the inside out with a garden hose — never a pressure washer, which folds the thin aluminum fins flat and makes cooling worse. Our guide to cleaning your air conditioner coils walks through the steps.
5. Listen for the capacitor — the hum test
Stand by the outdoor unit when it tries to start. If you hear a hum but the fan does not spin, the run capacitor is the prime suspect: it gives the fan and compressor motors their starting kick, and heat kills it more often than any other part. Push the fan blade gently with a long stick (never your hand) — if it spins up and keeps running, the capacitor is dead. A replacement is a $15–$40 part; photograph the wiring first and discharge the old one with an insulated screwdriver, because a charged capacitor can bite even with the power off.
6. Clear the condensate drain
Find the white PVC drain line near the indoor unit. If it drips slowly or not at all at the exit, it is clogged with algae, and the float switch shuts the whole unit down when the drain pan fills — which reads like a dead AC. Attach a wet/dry vacuum to the outside end for 30 seconds, then pour a cup of white vinegar down the access tee. Our guide to how to clean your HVAC condensate drain covers the float-switch reset.
7. Check the air coming out of the vents
Hold a thermometer at a supply vent and a return vent. A healthy system drops the air 15–20°F between the two. A drop under 12°F with a clean filter and clean coils points to low refrigerant or a failing compressor — both pro-only, because refrigerant handling needs EPA certification and a leak must be found, not just topped up. A normal drop but a house that still will not cool usually means duct leaks, a cheaper fix than any AC repair.
8. Read the error — blinking lights and codes
Modern furnaces and air handlers flash a diagnostic code on the control board. Count the blinks and match them to the chart printed inside the access panel — “3 blinks” might mean a pressure-switch fault, “7 blinks” an ignition lockout. Write the code down before you call: it tells the technician which part to bring, and tells you whether the problem is a $20 pressure switch or a $600 control board.
How Much Does AC Repair Cost?
These are the honest ranges homeowners pay in 2026; emergency summer rates run higher. Notice the pattern: the three most common AC repair jobs are all under $400, and the one that costs thousands is the compressor.
| Repair | DIY part cost | Typical pro cost (parts + labour) | Job time |
|---|---|---|---|
| Capacitor | $15–$40 | $150–$400 | 30 min |
| Contactor | $20–$50 | $150–$350 | 30–45 min |
| Condensate drain | $0–$20 | $75–$250 | 30 min |
| Refrigerant recharge (R-410A) | Not DIY (EPA licence) | $200–$600 | 1–2 hrs |
| Fan motor | $80–$200 | $300–$700 | 1–2 hrs |
| Control board | $100–$300 | $400–$700 | 1 hr |
| Compressor | Not DIY | $1,500–$3,000 | 4–8 hrs |
| Diagnostic fee (often waived) | — | $75–$150 | 30–60 min |
Two traps: never authorise a refrigerant “top-up” without a leak search — refrigerant does not get used up, so a system needing gas every summer has a leak. And get the quote in writing with parts and labour split out; a $25 capacitor should not appear as a $300 line item.
The Capacitor Spec Table — Match It Exactly
If check 5 pointed at the capacitor, the replacement must match the original’s ratings exactly. The label on the side of the old capacitor tells you everything — take a photo of it before you shop.
| Rating | What it means | Rule |
|---|---|---|
| 35/5, 40/5, 45/5 µF | Dual-run capacitance: first number runs the compressor, second the fan | Match both exactly |
| 370V or 440V | Maximum voltage rating | 440V can replace 370V; never go lower |
| Round vs oval | Case shape | Either works if it fits the bracket |
| 50/60 Hz | Frequency rating | Must match (US: 60 Hz) |
The detail only someone who has done this job knows: dual-run capacitors fail in summer heat, and the failure is often invisible — no bulge, no burn mark, no smell. The stick test in check 5 is the reliable diagnosis, not a visual inspection. Tighten the terminals firmly but do not over-torque the small screws; a loose connection arcs and kills the new capacitor within weeks.
AC Repair or Replace? The $5,000 Rule
Technicians use a simple rule: multiply the repair cost by the age of the unit in years. If the result is over $5,000, replacement usually wins. A $400 repair on a 12-year-old unit is $4,800 — repair it. A $900 repair on a 10-year-old unit is $9,000 — start getting replacement quotes. Three more factors tip the same AC repair decision: R-22 refrigerant (phased out, now $100+ per pound), energy bills climbing year over year, or a third AC repair in two summers. A new 16-SEER unit typically cuts cooling costs 20–30% against a 12-year-old 10-SEER unit — worth pricing in.
When to Call a Pro — and When to Stop
Stop DIY work immediately and call a professional if you hit any of these: a burning smell or visible scorching on wiring, the control board, or the disconnect — shut the breaker off and call. Refrigerant work of any kind — topping up, finding leaks, replacing lines — needs EPA Section 608 certification. A compressor that will not start, trips the breaker instantly, or grinds loudly — it is the most expensive part, and misdiagnosing it wastes money fast. Ice that returns within a day of a clean filter and a thawed coil. Anything involving the gas furnace — gas valves and heat exchangers are never DIY.
Everything else here — filters, breakers, drains, cleaning, and a capacitor swap — is fair game, and doing those AC repair checks first means you can describe the symptom and the code precisely instead of paying for an hour of diagnosis.
For step-by-step photos of the capacitor and contactor jobs, see Family Handyman’s guide to how to repair an air conditioner.
Frequently Asked Questions About AC Repair
How much does AC repair cost?
Most AC repair jobs cost $150–$400: a capacitor or contactor is the most common fix, a fan motor runs $300–$700, and a compressor replacement $1,500–$3,000. The diagnostic fee is usually $75–$150 and is often waived if you hire the same company. Get parts and labour split out in writing before authorising work.
Why is my AC running but not cooling?
The usual causes, in order, are a dirty air filter, dirty condenser coils, a frozen evaporator coil, or low refrigerant. Start with the filter and the outdoor coil — both are five-minute checks — and if the coil is iced over, turn the system off and let it thaw. If it ices up again within a day, call a pro: that means a refrigerant leak or a failing blower motor.
What is the most common AC repair?
Capacitor replacement is the single most common AC repair, especially in hot climates — heat degrades the capacitor until the fan or compressor hums but will not start. A contactor (the relay that switches the outdoor unit on) is a close second. Both are inexpensive, both take under an hour, and both are diagnosable with the hum test and stick test in check 5.
Is it worth repairing an AC or replacing it?
Use the $5,000 rule: multiply the repair cost by the unit’s age in years. Over $5,000, replacement usually wins — a $900 repair on a 10-year-old unit is $9,000 by that maths. Also replace if the unit uses phased-out R-22 refrigerant, if this is the third repair in two summers, or if a new 16-SEER system would cut cooling bills by 20–30%.
How long does an AC repair take?
Most AC repair visits take 30 minutes to 2 hours: a capacitor or drain clearing is under an hour, a fan motor or refrigerant recharge takes 1–2 hours, and a compressor replacement is a half-day job at 4–8 hours. If the technician needs to order a part, add a day or two — ask whether the part is on the truck before you book.
Final Thoughts
Most AC repair stories end the same way: a homeowner pays a diagnostic fee to learn that the filter was clogged or the capacitor was dead. Running the eight checks first costs you an hour and usually costs you nothing else — and when the problem really is a compressor or a refrigerant leak, you will walk into that pro visit knowing exactly what is wrong, what it should cost, and whether the $5,000 rule says repair or replace.
Keep a spare filter by the unit and note the capacitor rating on your phone. If your system is blowing warm air even after these checks, our guide to AC blowing warm air walks through the deeper causes, and cleaning your air conditioner coils once a season is the cheapest AC repair of all — the one you never need.