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.
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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. - DanielOn 2018-09-25 by Jenny
Nice article really very nicely explained that when is the right time to repair your AC and at what conditionsOn 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
MarvOn 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) -
RhOn 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 problemOn 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 elseOn 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 alsoOn 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 RUNOn 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 turningOn 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 upOn 2017-05-21 by (mod) -
BrettOn 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) -
VerleneOn 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 heatOn 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 noisyOn 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 problemOn 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.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 breakersOn 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: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 startOn 2016-01-30 03:00:02.930800 by Anonymous
Outside unit with inside unit working in heat positionOn 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 BillOn 2016-01-01 by Anonymous
heat or air want start but I have emergency heatOn 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 workingOn 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....
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