Your air conditioner is not turning on because it gets no cooling call or no power: usually a thermostat setting, a tripped breaker, an outdoor disconnect left off or a safety switch. Check those in order, reset a breaker once, and call (541) 461-2101 for Eugene, Springfield and Lane County or (503) 581-9982 for Salem, Keizer and Marion County.
We answer both lines 24 hours a day, 7 days a week. A hum or a click from the outdoor unit means a failed part. That is where your checks stop. Our technicians test the part with a meter, and we handle every repair behind the panel.
What should I check first when my AC won’t turn on?
Check the thermostat first, then the power, then the safety switches, in that order, and you won’t need tools or an open panel for any of it.
We run the same sequence on a no-cooling call, from the likeliest cause to the riskiest check. We check the thermostat call before we inspect any part. You can do the eight steps below the same way. The drawing shows where each one sits on the path power takes to the unit.
- Set the thermostat to Cool and the setpoint a few degrees below the room temperature. A thermostat left on Heat, Fan or Off is an easy mistake and a common false alarm.
- Replace the thermostat batteries if the screen is faint or blank. Cancel any schedule or hold that is setting a high temperature.
- Check whether the power is out. After a storm or heat-wave outage, look at your utility’s outage map: EWEB in Eugene, SUB in Springfield, PGE or Salem Electric in Salem and Keizer.
- Open the breaker panel and look for the AC breaker, usually a double breaker, sitting between On and Off. Push it fully off, then fully on. Once. We check that same breaker first on every call.
- Walk to the outdoor unit and check the disconnect box on the wall beside it. The switch or handle should be in the On position. Leave the cover’s inside alone.
- Check the indoor unit’s access door. Many air handlers and furnaces have a switch that cuts power when the blower door is loose or off. Reseat the door until it clicks into place.
- Look at the drain pan and the float switch. A full pan trips this switch and shuts cooling down on purpose. Mop up standing water, and read the drain section below on why it will trip again.
- Pull the filter. A choked one rarely stops a system outright, but ENERGY STAR says to inspect, clean or change it monthly in the cooling season, and a clean one rules out an airflow problem.
Give the system several minutes after any fix. Many controls hold the compressor off briefly after power returns, so you may see nothing at first. Quiet doesn’t mean dead. If all eight pass and the thermostat still shows a cooling call, we test the wires between the thermostat and the unit.
Why won’t my AC turn on when the thermostat is on?
A lit thermostat only proves it has power. It doesn’t prove the cooling call reaches the outdoor unit.
We check the Y call first. It starts the compressor. When you set the thermostat to Cool, it connects the red R wire to the yellow Y wire. InspectApedia lists R as the 24 volt supply from the transformer, Y as the cooling call to the compressor relay and G as the indoor blower. The Y call energizes the contactor coil outside, and SERVICE magazine explains that the contactor then switches line voltage to the compressor and the condenser fan.
Wire colours are a convention, not a guarantee. Our technicians check the terminal letter on the board, never the colour alone. We check each terminal against the equipment’s own wiring label. We test for 24 volts at the contactor coil to learn whether the call arrives. When a thermostat stays blank with fresh batteries, we test the transformer and the control board, and we replace the one that shows no 24 volts. PickHVAC adds that a blown 3 to 5 amp fuse on the control board, or a short in the thermostat wiring, can kill the 24 volt supply.
If the call is fine and the outdoor unit stays dead, power may be stopping before it reaches the unit, even when the breaker looks normal.
Why is my AC not turning on even though the breaker is fine?
Power can stop at three places beyond the breaker: the outdoor disconnect, the indoor door switch and a blown control fuse.
The disconnect is the box on the wall beside the condenser, and someone may have switched it off during yard work or a service visit. Check the box yourself. Don’t open it. The indoor access door matters too. PickHVAC says the blower compartment door has an interlock switch that cuts power when the panel isn’t seated correctly, so we check that switch before anything else on a dead indoor unit. It’s cheap to rule out. We also check the disconnect handle and the control fuse on every dead-outdoor-unit call. You can press the panel in until it clicks. We replace the interlock switch when it wears out.
A fuse is the third place. Some systems use a fuse rather than a breaker. A blown one breaks the circuit as completely as a tripped breaker does. We diagnose why a fuse blew before we replace it. Never bypass a safety switch to get the air back. Each one exists to prevent a hazard.
If a breaker did trip, the next question is how to reset it without making the fault worse.
How do I reset my AC?
Turn the thermostat to Off, switch the AC breaker fully off and back on one time, then set the thermostat to Cool.
Don’t reset it a second time. A breaker protects a circuit from overcurrent, so every forced reset repeats whatever fault tripped it. If the breaker trips again, leave it off. The cause sits inside the system, in a shorted motor, a failed compressor or damaged wiring, and we test the motor, the compressor and the wiring with a meter. We run one reset on a service call, never a string of them. We check the wiring after a second trip, and a breaker that trips right away is a technician call, not a second attempt.
If the breaker holds and the unit still stays silent, look at the drain pan, because a full one switches the AC off on purpose.
Can a clogged drain line stop my AC from starting?
Yes. A full drain pan trips the float switch, which opens the 24 volt control circuit and keeps the AC off.
The float switch is a small safety device in or above the drain pan. When the condensate line clogs and the water rises, the switch cuts the control circuit so the AC can’t flood your ceiling. Both the outdoor unit and the indoor blower go quiet. It looks like a dead system.
Wiping the pan brings cooling back for a while. The clog is still in the line, so the water rises and the switch trips again. We inspect the pan, the drain line and the switch together. We clean first, and we replace only what fails its test. Our technicians clean the drain line and test the switch, and we replace the switch when it fails the test. Pick Comfort lists float switch replacement in the cost table below. If water is also pooling outside the pan, read why an air conditioner leaks water.
When the pan is dry and the indoor fan runs but the outdoor unit won’t, the trouble sits outside.
Why does my outside AC unit hum or click but not start?
An outdoor unit that hums or clicks while the fan stays still almost always has a failed capacitor or a worn contactor, and both are technician-only parts.
SERVICE magazine says a humming compressor or fan motor that won’t turn over almost always points to a failed run or start capacitor. A click with nothing after it can mean a contactor whose contacts have pitted or welded. The capacitor helps the motors start and run, and the contactor is the relay that switches the outdoor unit on.
Neither part is a homeowner job. Leave the panel closed. This Old House notes that a capacitor stores electricity even when disconnected from power, and SERVICE magazine calls the charge lethal. Our technicians test the capacitor with a meter instead of guessing from the fan. We inspect the contactor contacts for pitting and welding, and we replace whichever part fails. We handle the capacitor, the contactor and the compressor on the same call. Switching the breaker off at the panel doesn’t make it safe. We test the capacitor before we condemn the motor, because SERVICE magazine says to replace a failed capacitor before blaming the motor.
Set the thermostat to Off while you wait. It matters. SERVICE magazine says a weak compressor capacitor can burn the compressor windings over time, so a unit that keeps trying to start isn’t harmless.
A hum is one story. The most common story in Oregon, though, starts with the weather.
Why won’t my AC start after a power outage?
After an outage, a tripped breaker, lost thermostat settings or a surge-damaged control board usually keep the AC off.
Winter wind and ice storms stress the Willamette Valley grid. So do summer heat waves. You may meet this problem in either season. Power returns to a thermostat that may have lost its schedule or Wi-Fi, to a breaker that tripped, and sometimes to a control board hurt by the surge, which we inspect on every storm call. We inspect the outdoor disconnect after a surge too. Run through checks 1 to 5 first, then wait. Give it several minutes. On a storm call we check the breaker and the thermostat first. If the thermostat stays dead with good batteries and the breaker holds, we test the control board and the 24 volt transformer next.
If the unit still refuses to run, the symptoms below point to the cause.
What does each AC no-start symptom mean?
Find the row that matches what you see. You’ll know whether the fix is yours. Silence points to power or a safety switch, while a hum or a click points to a failed part. We service every row in the last column.
| What you notice | Likely cause | Safe to DIY? | Professional fix |
|---|---|---|---|
| Thermostat blank, fresh batteries | Failed thermostat, or a dead low-voltage transformer or control board | Batteries only | Test the 24 volt supply, replace the failed part |
| Thermostat fine, nothing runs, panel door loose | Door safety switch open | Yes, reseat the door | Replace a worn switch |
| Nothing runs, water in pan | Float switch tripped by a clogged drain | Wipe the pan, nothing more | Clear the line, test or replace the switch |
| Breaker tripped once | Overload or short | One reset | Find the fault if it returns |
| Indoor fan runs, outdoor unit silent | Disconnect off, or failed contactor | Check the disconnect only | Replace the contactor |
| Outdoor hum, no fan or compressor start | Failed capacitor | No | Discharge and replace the capacitor |
| Breaker trips again right away | Shorted compressor or wiring | No | Electrical diagnosis, possibly compressor |
| Ice on lines or weak air before it stopped | Frozen coil | Thaw only | Thaw the frozen coil first |
If the system ran but cooled poorly before it quit, start with weak airflow from vents or an AC blowing warm air. Once you know which row you’re in, the next question is the bill.
How much does it cost to fix an AC that won’t turn on?
A capacitor averages $175 and a compressor averages $1,200 in national cost guides, so the failed part sets the bill.
These figures aren’t James Heating and Air Conditioning prices, and Oregon labor can run above or below them. We diagnose first. Then we quote a firm price.
| Repair | Typical range | Source |
|---|---|---|
| Thermostat replacement | $85 to $300, average $200 | Fixr |
| Float switch replacement | $150 to $550 | Pick Comfort |
| Capacitor | $80 to $400, average $175 | This Old House |
| Contactor | $75 to $450, average $180 to $300 | PickHVAC |
| 24 volt transformer | $45 to $500, average $120 to $220 | PickHVAC |
| Control board | $120 to $1,200, average $350 to $650 | PickHVAC |
| Compressor | $800 to $2,800, average $1,200 | Bob Vila, citing Angi and HomeAdvisor (2023) |
A capacitor or contactor is a modest repair. A compressor is the one to weigh against the age of your system, so we check how old your unit is before we quote one. The U.S. Department of Energy’s Building America guide says that when a repair costs more than half of a replacement, you should replace. We run that math with you before you agree to a compressor quote. No surprises.
When should I call a technician for an AC that won’t turn on?
Call as soon as the eight checks fail, the breaker trips twice, or the outdoor unit hums or clicks without starting.
Past those checks you need a licensed technician and a meter. Don’t guess. James Heating & Air Conditioning has served Lane County since 1983 under Oregon CCB #47396, and we answer both numbers around the clock. We repair air conditioners in Eugene, Springfield, Salem and Keizer. See our air conditioning repair service, or read about 24-hour AC repair when a problem can’t wait. When you call, tell us what you hear, what the thermostat shows and whether the breaker tripped.
- Eugene, Springfield and Lane County: (541) 461-2101
- Salem, Keizer and Marion County: (503) 581-9982
Frequently asked questions
Why does my AC click but not start?
A click with no fan or compressor usually means the contactor is closing but the motor can’t start, or the contactor is worn. A failed capacitor is the usual reason for a hum or click without a start. Both are technician repairs, and we test them with a meter.
Why is my AC unit not turning on but the fan is running?
The indoor fan runs on its own call, so the outdoor unit may have lost power or a part. Check that the outdoor disconnect is On and the breaker hasn’t tripped. If both are fine, we inspect the contactor, the capacitor and the motor, and you shouldn’t open the unit’s electrical panel.
Can I fix an AC that hums but won’t start myself?
No. The capacitor holds a charge even with the power off. We test it, replace it if it has failed, and check the contactor and the motor at the same time.
Why won’t my AC turn on after I changed the thermostat batteries?
Fresh batteries fix only a battery-powered display, and you’ll know quickly whether they did. If the screen is still blank or the system stays off, the thermostat may have lost its 24 volt supply to the transformer or control board, which our technicians test.
Should I turn my AC off while I wait for a technician?
Yes. Set the thermostat to Off so the compressor stops trying to start against a failed part. We answer both lines around the clock, so you don’t have to wait for morning to book.
