Why won't my air conditioner turn on?
Usually it's power or controls: a blank thermostat, a furnace switch or blower door that's off, a tripped breaker, a pulled outdoor disconnect, or a float switch tripped by a clogged drain. On hot afternoons an Xcel Saver's Switch or AC Rewards event can idle it. Past that, suspect a capacitor or contactor.
Key points
- Figure out what isn't running first: nothing, only the outdoor unit, or everything after a water backup.
- Check the thermostat, the furnace switch and blower door, both breakers and the outdoor disconnect.
- Xcel Saver's Switch and AC Rewards events can idle the outdoor unit on hot afternoons.
- A breaker that trips again after one reset means stop and call; don't keep resetting it.
- Our $79 trip charge is waived when you approve the repair, with a written price before work starts.
An air conditioner that won't turn on usually has a power or control problem you can check yourself: the thermostat, the furnace service switch and blower door, two breakers, the outdoor disconnect and the condensate float switch. On hot afternoons, an Xcel Saver's Switch or AC Rewards event can also hold the outdoor unit off on purpose. If all of that checks out, the usual culprit is a failed capacitor or contactor in the outdoor unit.
Start by working out which part isn't running. With the thermostat calling for cooling, stand by a supply register, then go outside to the condenser. You'll land in one of three places: nothing runs at all, the indoor fan runs but the outdoor unit doesn't, or everything was running and has now shut down with water around the furnace. Each points to a different short list.
Quick guide: what you see and where to look
| What you see | Where to look | Safe to check yourself? | Next step |
|---|---|---|---|
| Thermostat screen blank | Batteries, furnace switch, furnace fuse, C-wire | Batteries and the switch, yes | Technician if the fuse keeps blowing |
| Screen on, nothing runs | Furnace switch, blower door, furnace breaker | Yes | Technician if the breaker trips again |
| Indoor fan runs, outdoor unit silent | Utility event, AC breaker, disconnect, thermostat wire | Breaker and disconnect, once | Technician for wiring or a contactor |
| Outdoor unit hums, fan still | Capacitor or fan motor | No | Turn cooling off and call |
| Everything off, water by the furnace | Float switch, clogged drain, failed pump | Clearing a drain, often | Technician for a pump or repeat clogs |
| Breaker trips as the AC starts | Compressor can't start, or a shorted winding | One reset only | Leave it off and call |
What should you check when nothing on the AC runs?
Check the thermostat. A blank screen means no power. Battery-powered thermostats need fresh batteries. Thermostats powered by the furnace go dark if the furnace loses power or if the low-voltage fuse on the furnace control board has blown. That fuse usually blows because a thermostat wire has shorted somewhere, often the thin cable out to the condenser, so a new fuse that blows again points to a wiring fault. If your smart thermostat has been flaky since the day it went in, a missing common wire may be the root cause; our post on the thermostat C-wire explains it, and our thermostat service covers rewiring and replacement.
Check the furnace switch. Minneapolis basements almost always have a service switch for the furnace that looks like a light switch, mounted on the furnace, on a nearby joist, or at the top of the basement stairs. It gets flipped off by accident, often by someone reaching for the basement light. The AC won't run without the furnace, because the furnace blower moves the cold air.
Check the furnace door. Furnaces have a safety switch that cuts power when the blower door is off or not seated. If someone changed the filter and the door isn't fully latched, nothing runs.
Check the furnace breaker in the main panel.
Why is the outdoor AC unit silent when the indoor fan runs?
Now the problem sits between the furnace and the condenser.
- Wait five minutes. Many systems hold the compressor off for a few minutes after the thermostat is changed or power comes back.
- Check for a utility event. Electric service in Minneapolis comes from Xcel Energy. If you're enrolled in Saver's Switch, a device at the outdoor unit lets Xcel cycle the AC during peak summer demand. If your smart thermostat is enrolled in AC Rewards, the thermostat adjusts during events and usually says so on the screen. Either way, the outdoor unit can sit idle for part of a hot afternoon. Our AC Rewards review covers how those programs work.
- Check the AC breaker. The outdoor unit has its own two-pole breaker in the panel. If it's tripped, reset it once. If it trips again, stop there.
- Check the outdoor disconnect. The gray box on the wall near the condenser has a pull-out block, a lever, or in some older setups cartridge fuses. A pull-out block put back upside down, or a blown fuse, leaves the unit dead.
- Look at the thermostat wire. The thin low-voltage cable running to the condenser gets cut by string trimmers and chewed by animals, especially where it runs along the ground. A nicked wire means no signal to start.
If all of that checks out and the unit hums without the fan turning, or clicks and does nothing, it's likely a capacitor or contactor. Our post on AC humming noises explains the difference.
Why does the AC shut off with water around the furnace?
The AC coil drips water into a drain pan, and that water goes down a line to a floor drain or into a condensate pump. Many systems have a float switch in the pan, in the line or on the pump that shuts the AC off when water backs up, which protects your basement floor. Clear the clog or replace the failed pump and the AC comes back. Our guide to clearing a clogged condensate drain walks through it. If the line clogs again within weeks, the drain may lack a proper trap or slope, and that's worth having looked at.
What does it mean when the breaker trips as the AC starts?
Don't keep resetting it. A breaker that trips as the compressor starts usually means the compressor is drawing far more current than it should, because it can't start, has a shorted winding, or has a failed start component. Repeated resets heat everything in the circuit and can finish off a compressor that a capacitor or hard-start kit might have saved. A technician will also check that the breaker matches the maximum breaker size printed on the condenser's nameplate, which matters in older homes where the AC was added to the panel decades after the house was built. If the compressor turns out to be finished on an older system, our AC replacement cost guide shows what a new one involves.
What Minneapolis homes add to the list
- Tight side yards and alleys. Condensers wedged between houses or beside the alley collect dryer lint, cottonwood fluff and trimmer strikes. A clogged outdoor coil makes the unit run hot and trip on its safety limits.
- Older electrical. Houses from the 1910s through the 1930s had cooling added long after they were built, and the wiring and disconnects often show it. Loose or corroded connections at the disconnect are a common find.
- Shared condensate routing. Many older basements have one floor drain, and the AC and a high-efficiency furnace often share a condensate pump to reach it. When that pump quits, its safety switch can shut the AC down.
How much does it cost to fix an AC that won't turn on?
If the simple checks don't bring it back, the usual electrical repairs are modest. National cost guides like HomeGuide put a capacitor at $150–$400, a contactor at $200–$450, a condensate pump replacement at $100–$450 and a drain line flush at $75–$250. Those are typical national ranges, not our prices. Our capacitor replacement cost guide goes into the most common of them.
With us, a service call carries a $79 trip charge, waived when you approve the repair, and you get a written flat-rate price before work starts. Completed repairs carry our written 1-year parts-and-labor warranty.
When to stop and call
Leave the AC off and call a technician if:
- A breaker trips a second time after one reset.
- You smell burning, or see scorched wires or melted insulation at the disconnect.
- The outdoor unit hums while the fan sits still.
- A replacement fuse on the furnace control board blows again.
- Water has reached the furnace control board, wiring or an outlet.
What to do next
A service call in Minneapolis finds the cause without guesswork. Call 612-429-3465, 7am–9pm, seven days a week, or book AC repair in Minneapolis online. The same pricing applies across our whole service area, and our AC repair page lists what a visit includes. If the system runs but won't cool the house, see AC running but not cooling instead.
Questions
What should I check first if my AC won't turn on?
Start with the thermostat screen and settings, then the furnace service switch and blower door, then the AC and furnace breakers and the outdoor disconnect. Look around the furnace for water that may have tripped a float switch. If a breaker trips again after one reset, leave it off and call.
Why does my indoor fan run but the outdoor unit won't start?
The outdoor unit isn't getting power or a signal. Common causes are a tripped AC breaker, a pulled or blown disconnect, a cut thermostat wire, a failed contactor or capacitor, or a utility event if you're enrolled in Xcel's Saver's Switch or AC Rewards. Turn cooling off if the outdoor unit hums without the fan turning.
Can a clogged drain stop my AC from turning on?
Yes. Many systems have a float switch in the drain pan, drain line or condensate pump that shuts off cooling when water backs up. It's there to keep water off your basement floor. Clearing the clog or replacing a failed pump usually brings the AC right back.
Does Xcel's Saver's Switch stop my AC from running?
Yes, for part of the time during a control event on a hot summer afternoon. Saver's Switch cycles the outdoor unit off and on, so the indoor fan may run while the condenser sits idle. That's expected for enrolled customers. If the outdoor unit won't run in the evening or on mild days either, the cause is something else.
Sources
- HomeGuide cost guides (2026 editions) homeguide.com