Set #2 of Q&A on what to do when your air conditioner or heat pump won't start:

These FAQS about what to check if your air conditioner or heat pump won't start or won't run or just hums can help diagnose and fix the trouble.

This article forms part of our series on how to diagnose an air conditioner or heat pump that is not cooling: this article explains how to diagnose and correct air conditioning problems like lost or reduced air conditioner cooling capacity, reduced or no cool air flow, reduced or no actual lowering of the air temperature, or an air conditioner that won't start.

We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Air Conditioner / Heat Pump Won't Start FAQs

These reader comments, questions and answers about diagnosing and fixing an A/C or heat pump unit that won't run or won't start were posted originally

at AIR CONDITIONER WON'T START - home; be sure to review that article.

On 2019-07-04 by (mod) - New compressor installed; everything is running, but no cold air.

Surely your installer will return to diagnose and fix. Perhaos clogged TEV

On 2019-07-04 by Pat Stroschein

New compressor installed; everything is running, but no cold air. Freon is full.

On 2019-07-02 by (mod) -

I think a service tech would check first for a loose wire or connector and second for a bad relay control

On 2019-07-01 by claude

carrier hv4b air handler fan motor is a variable speed motor. It now only works on low speed in cooling mode ,but works in all speeds in heating mode. It did work on all speeds depending on demand.Also fan does not run on fan on. Don't know if this is related problem

On 2019-06-13 by (mod) - fan inside on but no air flow

Tony

When a circuit breaker has tripped that usually means there's an overcurrent. Even if you can turn the AC back on by resetting the breaker there is an underlying problem that needs to be found and repaired. It's time to call for service.

On 2019-06-12 by tony

Im in office building. each unit has own ac unit outside. turned on work for two days no problem. Today stop cooling. fan inside on but no air flow. air unit outside nothing. no sound when turned on. I check panel for trip switches. On left side label A C right side had two single switches together. label a c and heat. look this switch was tripped.
T

On 2019-05-01 by (mod) - AC wouldn’t go off without us turning it off at the breaker.

Perhaps you could ask your technician to check and eliminate any possibility of a problem with the thermostat wires themselves

On 2019-04-30 2 by Alice

I meant to say it wouldn’t go off without us turning it off at the breaker.

Hi. Neither the inside nor the outside unit will come on. We’ve changed out the thermostat. Any idea what else we can do? Our repairman had it running and then it stopped. When he came out, the outside unit wouldn’t go off with us turning it off at the breaker. He replaced a part to help with that. Now this new problem. Oh and the thermostat will go blank without batteries. It had stopped doing that too.

On 2018-12-09 by Anonymous

Have you checked the dip switches on the control board to be sure they're suck correctly as by the owners manual?

On 2018-12-09 by Dennis

Blowers fan turns on before burners heats up carries model 58gc030-EB

On 2018-11-21 by Danny

Heater will not turn on until outside temperature reaches about 50 degrees. Does this everyday like clockwork.

On 2018-11-03 by (mod) -

Recently-posted questions and answers that appeared on this page are now at

AIR CONDITIONER WON'T START FAQs-2 inspectapedia.com/aircond/Air_Conditioner_Wont_Start_FAQs2.php

On 2018-09-25 by (mod) -

Thank you for the nice comment, Jenny. We are pleased when our research and writing prove useful to you. - Daniel

On 2018-09-25 by Jenny

Nice article really very nicely explained that when is the right time to repair your AC and at what conditions

On 2018-07-11 by Nancy

Unit quit. How power on it.

On 2018-07-06 by (mod) -

So glad to hear it Lloyd.

On 2018-07-06 by Lloyd Hammond

Thanks for the tip about the condensate - I had quite a bit of water in the overflow pan and once I cleared it out the a/c unit worked again.

On 2018-05-04 by (mod) - check the current draw of the compressor/condenser motor

Marv

Your service tech might check the current draw of the compressor/condenser motor - the compressor could be seized

On 2018-05-03 by Marvinls sr 4-ton Goodman

i have a 4-ton Goodman unit and the contactor failed and the unit quit, concator was replaced, unit did not restart so changed the capacitorand still nothng. after rechecking the contactor,

there is power coming in from the house but nothing going to the capacitor, no power on the side or on top and the power had ben turned on...help...

On 2018-02-11 by (mod) -

Rh

At very low outdoor temperatures your outdoor equipment may, quite properly, refuse to run as doing so could damage it.

On 2018-02-11 by Rhmona

My a/c fan and heat are working, but when I put on cold it's not coming on inside or out. What could be problem

On 2018-01-10 by (mod) - thermostat is set to HEAT and the heat pump does not run

If the thermostat is set to HEAT and the heat pump does not run, and if outdoor temperatures are not below its operating range, and if the system worked in cooling mode, I suspect that's a control board problem.

On 2018-01-09 by Michael

Compressor will start on cool cycle but not on heat cycle.

On 2017-10-14 y (mod) -

Perhaps a failed contactor relay, or bad control board, or of course something else

On 2017-10-14 by Jerry

On a split home AC, the outdoor unit with compressor and fan, both are hot but won't run. There is no humming sound. I spun fan with a screw driver, it still would not start.

This makes me thing the capacitor isn't the problem. The thermostat properly opens and closes the electromagnetic contact points.

On 2017-09-04 by William

I have Carrie ac unit at 12:00 am every morning it shouts down and only the out side unit will run no matter what I try to cut it on only the out side unit will run around about 6:00 am the inside unit will finally run what can that be.

On 2017-07-16 by Kevin

Have 2year old Goodman ac with heat pump the outside unit stopped blowing the thermostat in house says system cool on but nothing is coming out but new batteries in thermostat also

On 2017-06-17 by Paul kellogg

My outside unit was not working and I finally found that the indoor circuit breaker had failed in the "on" position- it would not flip off - contact was fused in a high resistance, closed position. Providing 87 volts rather than 240. Newer saw a circuit breaker fail like that.

On 2017-06-12 by (mod) -

To find our appropriate article I used the Search InspectApedia box above to look for COMPRESSOR FAN WON'T RUN
to bring up

FAN, COMPRESSOR / CONDENSER UNIT - at https://inspectapedia.com/aircond/HVAC_Condenser_Fan.php where we discuss the causes of a fan that just won't spin - usually if the motor spins freely by hand it's not seized so a technician swaps in a new start/run capacitor and maybe a fan relay.

On 2017-06-12 by James

My Heatpump unit compressor fan is not running. what problems could this be ? Can you name, the possiable cause ?

On 2017-06-11 by Jimi

I just started my ac unit for first time cool air coming out but notice compressor fan is not turning

On 2017-06-06 by (mod) -

It sounds as if your system may have been running on backup heat and that the compressor condenser unit is not functioning

. If you hear a compressor condenser unit outside appearing to run normally but only warm air is being delivered, there are other possible causes such as failure to switch to cooling mode, a problem with the thermostatic expansion valve or reversing valve, or lost refrigerant.

On 2017-06-04 by Judy

When switching to air from heat the check heat pump message keeps coming up

On 2017-05-21 by (mod) -

Brett

While there are some common blinking-code meanings across HVAC systems like "dirty filter", to actually figure out what your system's blink codes mean we need, besides the manufacturer (LG heat pump) also the model - thus we can find the owners' manual to find the table of light codes or error codes.

On 2017-05-21 by Brett Stansfield

Our LG heatpump blinks cooling then it blinks heating. Ive cleaned the filter but still no joy. Any ideas?

On 2017-01-08 by Anonymous As soon I put the switch back in. It trips the breaker

I have a heat pump. The outside unit is on one breaker. An the inside unit is on another breaker. The out side unit is tripping the breaker. An when I try to reset it it immediately trips again. I don't even have time to get my finger off it before it trips. O can pull the disconnect switch an it won't trip

As soon I put the switch back in. It trips the breaker. I can leave the disconnect switch in an unhook the 3 wires to the compressor at the control panel on side of unit. An the breaker doesn't trip. But soon. As put the wires back on the breaker will trip. Other than having a bad compressor. Can anything else cause this problem.

On 2016-11-24 y Anonymous

I have a Bryant ac/heat pump when you set on cool at heat cycle the unit will not start.you barly feel air flow through floor vents.And hear the eva fan running but the condenser fan won't run. Thermostat seems to be working can hear it click when you turn it on.I have 240 volts at the ac unit and the capacitor base 120 @all 3wires.can anyone help me out with this problem thanks Butch

On 2016-07-31 14:20:25.222381 by (mod) - I changed the fan control board a couple years back. Would this board have the only relay?

I don't know your specific brand and model of AC system but there are various relays and control boards: in the air handler, in the compressor/condenser relays operate the compressor motor not just the fan.

On 2016-07-31 by Phil

Thanks. I changed the fan control board a couple years back. Would this board have the only relay?

On 2016-07-30 by (mod) -

Perhaps your unit has a bad control relay.

On 2016-07-30 by Phil

My outdoor unit comes on but the inside blower will not. I flip the breaker at the indoor unit and the inside blower kicks on.

On 2016-01-04 by (mod) -

Brian

If the thermostat is properly set and outdoor temperatures are not lower than its operating range, the heat pump should be working (if it is a heat pump and not just an AC unit). Keep in mind that a thermostat may say "HEAT" mode but if the unit installed is just an A/C unit some other heater has to be switching on - such as a separate furnace, boiler, or backup heating system.

If your system is truly a heat pump and it won't heat and the thermostat settings are correct and if outdoor temperatures are not below the heat pump's operating range, I expect your service tech will check for a bad outdoor temperature sensor, control, or relay.

On 2016-01-04 by Brian

My heat pump will not come on in heat mode. I can't hear any kind of buzzing at the outdoor unit either. The system works fine in A/C mode. The auxillary heat works as well, but the outside unit will not come on for heat.

On 2016-11-13 by (mod) -

Verlene

If your heat pump indoor our outdoor unit is sparking when you try to turn it on the system is unsafe, risking fire or shock or injury or worse, so you should leave it turned OFF while waiting for diagnosis and repair by a trained HVAC service tech.

On 2016-11-13 by (mod) -

Rhonda,

If you're sure that your system is indeed a heat pump, not a straight air conditioner, and if you're sure that the thermostat is calling for heat, then either there is a control problem or relay problem in the heat pump unit or the outdoor temperature is low enough that your system wants to run on backup heat and it's the backup heat that's not working.

Use the search box just above and search InspectApedia.com for BACKUP HEAT for HEAT PUMPS to read details.

On 2016-11-13 by rhonda

heat pump wont blow out any heat it works on air and dry but no heat

On 2016-10-13 by verlene

I have a goodman heat pump wont heat up.it sparks fan kicks on . No heat. Propane tank is full what could be the problem.

On 2016-08-30 by Anonymous

condeser fan noisy

On 2016-08-26 by Lance - air handler in the attic is not coming on,

The air handler in the attic is not coming on, the outdoor unit outside works but it's the inside that doesn't. What's wrong?

On 2016-06-28 by Latif

My Sanyo split a/c compressor sometimes do not work how to prepaid this falt pls send me some ideas to solve this problem

On 2016-06-22 by (mod) - my air juststopped working my fan on the unit is working

If the outside compresosr/condenser is not working or if there is a refrigerant leak the system won't cool.

Turn everything off for 45 minutes. Then try once more. If the outside unit runs and inside blows cool air, repair is still needed but you may get some cooling.

Else use some portable fans to cool things a bit and leave the system off

On 2016-06-22 by brandg

What do i do,my kids are hot over here....my air juststopped working my fan on the unit is working but on my thermostat says low what do i do,already checked breakers

On 2016-06-01 by (mod) - suspect a bad motor capacitor

Replacing the cap is a low cost thing to try first.

On 2016-06-01 by JJC

We have a trane R22 heat pump and the blower fan (internal) is acting up. I shut the power (three breakers) to the it and let it rest for about an hour.

Then powered it up and the blower will start when I turn the thermostat from "auto" to "fan on".

The compressor will turn on when I turn it to cool. However, I don't believe the blower is fully operating as I get marginal airflow.

After an hour or so, the blower fan continues to operate but at a very minimal speed. I was going to change the fan blower start capacitor but am now suspecting the blower motor too as I don't think the fan should slow down so significantly over time

. Would a bad capacitor do this or is both the capacitor and blower motor bad?

On 2016-04-05 01:18:52.340245 by (mod) -

Two guesses:

1. you reset the control board and maybe cleared an error condition

2. the compressor was unable to start against high head pressure that relaxed during its time off

On 2016-04-04 by Trade

My heat pump has not kicked on the last few weekends although the thermostat showed heat. A freind said turn the main breaker to off, wait 20 min. Turned it to on and approx. 5 min later it started. Why was that?

On 2016-03-15 by Anonymous

I have a split unuit in a single wide mobile home everything is working on air handler ..... the out door unit clicks but compressor wont start

On 2016-01-30 03:00:02.930800 by Anonymous

Outside unit with inside unit working in heat position

On 2016-01-0 by (mod) - heat or air want start but I have emergency heat

Anon if your heat pump outdoor unit won't start it might be because the outdoor cold temperature is below that unit's operating range - leaving you with backup heat only. See my note below to Bill

On 2016-01-01 by Anonymous

heat or air want start but I have emergency heat

On 2015-12-28 by (mod) -

Bill if outdoor temperatures where you live are very low the system may be acting normally; if not there may be a control board, relay, or temperature sensor problem to be found and repaired.

On 2015-12-28 9 by Bill Foster

Outside ac unit Will not kick on back emergency heat working

On 2015-11-21 by Anonymous

Look for a bad control biard, relay, or in cold weather backup heat not working.

On 2015-11-21 by denny

our heat pump wont kick on in the heat position.

...

Continue reading at  at AIR CONDITIONER WON'T START - topic home - diagnostic procedures, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX. Or see these

Air Conditioner or Heat Pump Won't Start or Won't Run Articles

• DIAGNOSTIC GUIDE A/C or HEAT PUMP
  • AIR CONDITIONER BLOWS WARM AIR
  • AIR CONDITIONER WON'T START
  • BURNED-OUT COMPRESSOR
  • CAPACITORS for HARD STARTING MOTORS
  • CONDENSATE PAN OVERFLOW SWITCH
  • CONDENSER FAN WON'T START
  • ELECTRIC MOTOR DIAGNOSTIC GUIDE
  • FURNACE FAN WONT START
• COMPRESSOR / CONDENSER DIAGNOSTICS
• CONTROLS & SWITCHES, A/C - HEAT PUMP
• ELECTRIC MOTOR DIAGNOSTIC GUIDE

Suggested citation for this web page

AIR CONDITIONER WON'T START FAQs-2 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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