DIY troubleshooter · causes ranked by how often each turns out to be the problem, in our judgment (no dataset ranks them)
The system runs, air comes out of the vents, but the house stays warm or the air feels lukewarm. Start at the top of the list: the first four causes cost nothing to rule out, so check them before you pay for a service call.
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
Simplified drawing, not to scale. Real systems vary: the indoor unit can sit in an attic or closet, the ducts can run in the attic or under the floor. Original illustration, not a photo.
Stock photo, not our work. Photo by ready made via Pexels.
How to checkSlide the filter out and hold it up to a light. If you cannot see light through it, or it is gray and matted, it is choking the airflow across the indoor coil.
Typical repair costFree to check.
How to checkConfirm the display is on, the mode reads Cool, and the set point is at least 3 degrees below the room temperature. A fan setting of On blows unconditioned air between cooling cycles and feels warm.
Typical repair costFree to check.
How to checkLook at the condenser outside. Leaves, grass clippings, cottonwood fluff, or shrubs pressed against the fins keep the unit from shedding heat. Manufacturers commonly ask for about two feet of clear space on all sides; check your manual.
Typical repair costFree to check.
How to checkOpen the panel and look for a breaker sitting in the middle position. Air handler and condenser each have their own.
Typical repair costFree to check.
How to checkYou cannot measure refrigerant without gauges. Visible signs are ice on the larger copper line, hissing, oily residue at a fitting, or weak cooling that worsens over weeks. A sealed system does not use up refrigerant, so low charge means a leak.
Typical repair costRefrigerant leak repair: Median $1,320 (most $800–$3,000), 32 homeowner reports; Refrigerant recharge: Median $690 (most $460–$1,200), 48 homeowner reports
How to checkThe indoor fan runs but the outdoor fan is still, or the outdoor unit hums and clicks without starting. Homeowners should note the symptom and stop there.
Typical repair costCapacitor: Median $310 (most $220–$400), 26 homeowner reports; Compressor: Median $3,000 (most $1,900–$4,000), 43 homeowner reports
How to checkIce on the indoor coil or a warm, weak airflow with a clean filter. See the freezing-up guide; thawing is safe, finding why it froze is not a homeowner job.
Typical repair costEvaporator coil (indoor coil): Median $3,000 (most $2,000–$4,500), 57 homeowner reports
Ranks are editorial, not measured. A price is what homeowners reported for that one part or job, not a quote for the cause on that row, and a cause can involve more than one part. Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
$190
Median pro diagnostic visit, from 62 homeowner reports
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
These checks need no tools beyond a screwdriver, a hose, or a vacuum. Do them in this order.
2 Air filter
1 Thermostat
6 Outdoor unit: compressor, fan and condenser coil
7 Breaker panel and outdoor disconnect
The causes below are not DIY, and we give no repair steps for them. Each carries a specific danger.
Source: Stationary Refrigeration and Air Conditioning (Clean Air Act Section 608), 2026-09-30; retrieved 2026-09-30.
Never chip ice off a coil. The coil tubing is thin copper, and one puncture releases refrigerant, which brings you back to the Section 608 line above.
Stock photo, not our work. Photo by Anh-Bao Tran-Le via Pexels.
Open
Need a licensed HVAC pro in the Tampa Bay outer ring? Call and we'll connect you with a licensed local contractor.
HVACPro is a free referral service for homeowners, not an HVAC company. We don't do the work, and we may be paid by the contractor. Check any contractor's license on the state's lookup before you hire.
Every city below has an A-to-Z list of the businesses with an active Florida HVAC license there. The number on each chip is that count.
Counts: businesses with an active license and a city address in the Tampa Bay outer ring, from FL DBPR construction licensee extract (CONSTRUCTIONLICENSE_1.csv), retrieved 2026-10-05. A license says the state permits the work, not that the work is good.
A pro visit starts with a diagnostic fee. Homeowners reported: Median $190 (most $100–$290), 62 homeowner reports. The repairs behind the causes on this page:
Reported price, U.S. dollars
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
| Repair | Median | Most (middle half) | Reports |
|---|---|---|---|
| Refrigerant leak repair | $1,320 | $800–$3,000 | 32 |
| Refrigerant recharge | $690 | $460–$1,200 | 48 |
| Capacitor | $310 | $220–$400 | 26 |
| Compressor | $3,000 | $1,900–$4,000 | 43 |
| Evaporator coil (indoor coil) | $3,000 | $2,000–$4,500 | 57 |
These are national prices. We do not have enough Tampa Bay outer ring reports to publish a local one.
If the repair ends in a full replacement, the closest local cut is Florida: a median of $12,000 (most $9,400–$15,600) across 55 full-system reports, against $13,650 across 588 reports nationwide. See the AC repair cost guide and the AC replacement cost guide for every repair and job we have enough reports to price.
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
A pro fix for this symptom can end in a replacement. If it does, these Tampa Bay outer ring utility programs pay for qualifying equipment. Confirm your utility and eligibility first.
| Program | Utility | Amount |
|---|---|---|
| Home Energy Improvement: AC replacement | Duke Energy Florida | $300 |
| Home Energy Improvement: heat pump upgrade | Duke Energy Florida | $500 |
| Home Energy Improvement: strip-heat replacement (high efficiency) | Duke Energy Florida | $600 |
| Home Energy Improvement: strip-heat replacement (higher efficiency) | Duke Energy Florida | $1,000 |
| Energy Efficient Heat Pump Rebate | Lakeland Electric | $450 (mini split $225 per condensing unit) |
| HVAC Annual Maintenance Rebate | Lakeland Electric | Up to $100 per year (the cost of the inspection) |
| Heating & Cooling Program: standard tier | Tampa Electric | $40 for SEER 16.0 / SEER2 15.2 |
| Heating & Cooling Program: high-efficiency tier | Tampa Electric | $550 for SEER 17.0 / SEER2 16.2 |
Stock photo, not our work. Photo by Bingqian Li via Pexels.
Check three things first: the air filter, the thermostat settings, and the outdoor unit for debris on its coil. Trane lists a clogged filter, a thermostat set incorrectly, and a clogged or blocked outdoor coil among the causes of an AC that runs but does not cool.
Trane also lists low refrigerant, most likely from a leak, and a faulty run capacitor. Both of those need a trained technician, and adding refrigerant requires EPA Section 608 certification.
Checked against: Trane: AC Fan Not Working? Reasons Why It Stopped Spinning; Trane: Air Conditioner Troubleshooting: 5 Common Issues; U.S. EPA: Homeowners and Consumers: Frequently Asked Questions. Pages opened 2026-09-30.
No. EPA says Section 608 certification is required to recharge appliances, and refrigerant for stationary appliances is sold only to certified technicians or the companies that employ them. EPA also prohibits knowingly venting refrigerant while servicing equipment. Trane says low refrigerant most likely means a leak, and EPA advises asking your technician to locate and repair the leak instead of topping it off.
Checked against: Trane: Air Conditioner Troubleshooting: 5 Common Issues; U.S. EPA: Homeowners and Consumers: Frequently Asked Questions; U.S. EPA: Refrigerant Sales Restriction; U.S. EPA: Section 608 Technician Certification Requirements. Pages opened 2026-09-30.
Check the filter every month, especially in heavy-use months such as summer. If it looks dirty after a month, change it. At a minimum, change it every 3 months.
Checked against: ENERGY STAR (EPA/DOE): Heat & Cool Efficiently; ENERGY STAR (EPA/DOE): Maintenance Checklist (heating and cooling). Pages opened 2026-09-30.
A failed capacitor is one likely cause. Trane says a failed start capacitor can make the motor hum loudly, and a bad capacitor can leave the unit running with the fan not spinning. A burned-out fan motor is another cause.
Trane says only a trained HVAC professional should test, discharge, or replace a capacitor, and OSHA requires capacitors to be discharged when their stored energy might endanger personnel. Turn the system off at the thermostat, leave the panel closed, and call a technician.
Checked against: OSHA: 29 CFR 1910.333, Selection and use of work practices; Trane: AC Fan Not Working? Reasons Why It Stopped Spinning; Trane: All About Heat Pump Capacitors and Signs of Trouble. Pages opened 2026-09-30.