10 Common A/C Problems and What They Mean
When your air conditioner acts up during a Twin Cities summer, you want answers fast. We have a reputation for bitterly cold winters in Minnesota, but if you live here, you know our summers can be just as brutal.
The good news is that a lot of common A/C problems have simple explanations, including a few you can check yourself before you pick up the phone.
Below are 10 of the problems we see most often, what each one usually means, and when it makes sense to call a licensed technician. Think of it as a quick A/C troubleshooting guide for Minneapolis, St. Paul, and the surrounding metro.
A/C Problem 1: Your A/C is blowing warm air
You set the thermostat to cool, but the vents are pushing out room-temperature air. Start with the easy checks: make sure the thermostat is set to “cool” and not just “fan,” then look at the filter, since a dirty one chokes off airflow. One local culprit this time of year is cottonwood. If fluff has coated your outdoor unit, rinse it off gently with a garden hose. Never use a pressure washer, which can bend the fins.
Call Bonfe if: The system is low on refrigerant. That points to a leak in a sealed system, and it is not a do-it-yourself fix.
A/C Problem 2: Your A/C won’t turn on at all
No air, no hum, nothing on the thermostat screen. Work through the simple causes first: check the breaker panel for a tripped breaker, the outdoor disconnect near the condenser, and the batteries in your thermostat. A badly clogged filter can sometimes trigger a safety shutoff, too.
Call Bonfe if: A breaker trips again right after you reset it. A breaker that keeps tripping is flagging an electrical problem, not asking to be switched back on.
A/C Problem 3: Ice or frost on the indoor unit or refrigerant line
You notice frost, or even a solid block of ice, on the line coming off your unit. Icing up usually traces back to restricted airflow (a dirty filter, closed vents, or a struggling blower) or to low refrigerant. Turn the system off, run the fan only to let everything thaw, then replace the filter and open your vents.
Call Bonfe if: You see ice at all. We recommend calling us right away. Thawing it improperly can damage the control board and may affect your warranty coverage.
A/C Problem 4: Water pooling near the indoor unit
There is a puddle around the furnace or air handler. Most of the time, this is a clogged condensate drain line backing up or a frozen coil that’s melting. A wet/dry vac at the drain exit can sometimes clear a minor clog, but this one usually warrants a call.
Call Bonfe if: The clogs keep coming back, you cannot find the drain line, or there is already water damage to a ceiling or floor.
A/C Problem 5: Strange noises
Your A/C has started making a sound it never used to. The noise itself is a clue. Banging or clanking tends to point to the compressor or blower. Rattling is often loose debris or a panel. Hissing can mean a refrigerant leak. Steady clicking suggests a relay or contactor, and a squeal usually points to a bearing. You can safely clear debris from around the outdoor unit and tighten any obviously loose screws.
Call Bonfe if: The sound is anything beyond simple rattling. Most of these need a trained technician to track down.
A/C Problem 6: Strange smells
Something coming through the vents smells off. A musty or sour odor usually means mold in the drain pan or on the evaporator coil. A burning, electrical smell can mean a wire, motor, or capacitor is overheating. A rotten-egg smell is the serious one, because it can signal a gas leak. For a mild musty smell, replace the filter and wipe down the accessible parts of the indoor unit.
Call Bonfe if: You notice burning or chemical smells, which need same-day service. If you smell rotten eggs, leave the house first, call your gas company, then call us.
A/C Problem 7: Your A/C keeps turning on and off
The system kicks on, runs for a minute, shuts off, and starts the cycle over. This pattern is called short cycling. Causes include a poorly placed thermostat, an oversized system, a dirty filter, a refrigerant problem, or a failing compressor. Replace the filter and make sure your registers are open.
Call Bonfe if: It keeps happening. Short cycling wears a system out quickly, so it is worth addressing sooner rather than later.
A/C Problem 8: One room won’t cool
Every room is comfortable except the one that never seems to cooperate. Often, the cause is duct-related: undersized or leaky ducts, a missing return, or a closed damper. Thin insulation in that part of the house can play a role, too. Confirm the vent is open, and try closing the vents in a couple of cooler rooms (just a couple, since more than that strains the system).
Call Bonfe if: The room never catches up. We can run a heat-load check, inspect the ducts, or talk through whether a mini-split makes more sense for that one space.
A/C Problem 9: Humidity stays high, even with the A/C running
The temperature reads fine, but the air still feels sticky. A few things can cause this: an oversized system, short cycling, or the fan set to “on” instead of “auto.” The “on” setting keeps blowing air across the moisture sitting in the drain pan and puts it right back into your home. Switch the fan to “auto” and replace the filter.
Call Bonfe if: Indoor humidity stays above 55% with the A/C running. That can point to a need for a dehumidifier or a properly sized system.
A/C Problem 10: Your bill is higher than usual
The A/C is running like it always does, but the bill came in noticeably higher. An aging system gradually loses efficiency, especially without regular maintenance. A small refrigerant leak can force longer run times, and sometimes a thermostat schedule simply got changed, and nobody noticed. Check the schedule and the filter, and compare this month against the same month last year in your electric utility’s app.
Call Bonfe if: Nothing obvious explains the jump. A licensed diagnostic ($99, fully waived if you move forward with the work) can pinpoint what is going on.
Why Twin Cities Homeowners Call Bonfe
Bonfe is a 100% family-owned home services company based in South St. Paul, serving Minneapolis, St. Paul, and the surrounding metro since 1993. Our licensed technicians handle plumbing, heating, cooling, electrical, and drain and sewer work.
- Family-owned for more than 30 years in the metro.
- 11,000+ Google reviews from Twin Cities homeowners.
- Regular rates from 7am to 10pm, seven days a week, with no evening or weekend upcharge.
- 24/7/365 emergency service for anything outside those hours.
- Lifetime Parts & Labor Warranty on our recommended repairs and installations.
- Upfront pricing, with all-in quotes after our team assesses the work in person.
Ready to skip the guesswork?
Whether your A/C won’t turn on, won’t cool, or just isn’t acting right, our team can help.