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Air Conditioning & Heat Pump troubleshooting questions with answers index

troubleshooting air condtioners and heat pumps

Below we have quick links to pages where problems and solutions are discussed for your quick reference. We hope you find a quick solution for your problem! Special thanks are in order for the many people who took the time to do the YouTube videos that are included on our pages! I know that it is much easier for me to learn if I can see the problem and repair through a video or picture! Near the bottom of each page there is an area that allows you to comment or ask questions. If you have any questions please email us anytime. Our email address is: support@arnoldservice.com. Comments are welcome below. We would love to help you out, answer your questions and earn your business! We Hope you have a blessed day! Steve & Barbara Arnold

One of my favorite quotes by David Jeremiah: “Nothing is more valuable than helping another person succeed!”

  1. Air conditioner troubleshooting flow chart (This is a troubleshooting flow chart to help you troubleshoot your air conditioner or heat pump)
  2. Air Conditioning and Heat Pump Troubleshooting Simplified
  3. Problem: Is it Normal for my heat pump to have frost on the outside? (With one DIY YouTube Video).
  4. Problem: My heat pump is making a funny noise. How does a reversing valve work? (With two DIY YouTube Videos).
  5. Problem: Noisy compressor heat pump in the winter time. Will a hard start booster help? (With one DIY YouTube Video).
  6. Air Conditioner Fan Replacement (Video)
  7. Air Conditioner Contactor Replacement (Video)
  8. Capacitor Testing Troubleshooting (Video)
  9. Furnace Control Board (Video)
  10. Furnace Blower Replacement (Video)
  11. How To Discharge a High Voltage Capacitor
  12. Problem: Your fan on your furnace runs all the time and will not shut off (With one DIY YouTube Video)
  13. Problem: Fan will not come on in the “ON” position or your fan will not come on when you turn the thermostat down
  14. Problem: Air Conditioning outdoor condensing unit or heat pump unit will not shut off. (With one DIY YouTube Video)
  15. What to Check for If Your Air Conditioning System is not Working
  16. Question: How do you find refrigerant leaks?
  17. Problem: Air conditioner is freezing up. Seeing frost or ice on the suction line (black insulated line) (With one DIY YouTube Video)
  18. Problem: Air conditioner or heat pump cycling off and on too much
  19. Problem: Furnace, air conditioner heat pump will not come on. Blown fuse on board. (With one DIY YouTube Video)
  20. Problem: Compressor will not run (With three DIY YouTube Videos)
  21. Problem: Air Conditioning outdoor condensing unit or heat pump unit will not shut off (With one DIY YouTube Video)
  22. Problem: The Air conditioner outdoor unit will not come on. Nothing happens. (With one DIY YouTube Video)
  23. Problem: Air conditioner or heat pump compressor will not start. Hear an UGGGG sound. (With one DIY YouTube Video)
  24. Problem: Outdoor condensing fan motor has stopped running. (With one DIY YouTube Video)
  25. Problem: My air conditioner heat pump is tripping the circuit breaker. Will a compressor hard start booster solve my problem?
  26. Problem: Outdoor air conditioning unit is running but the indoor furnace blower will not run. (With two DIY YouTube videos)
  27. Problem:The fan on the unit recently started running continuously at low speed. The only way I can stop it is to cut the power at the disconnect. (With one DIY YouTube video)
  28. Problem: My outdoor air conditioning unit’s high pressure switch trips ever so often. Why does the high pressure switch trip so often?
  29. Problem: Lights in our home dim when the AC starts. What could be the problem? (With one DIY YouTube Video)
  30. Problem: My outside AC unit is humming but no fan or compressor action. Sounds like I have a capacitor problem? (With one DIY YouTube Video)
  31. Problem: Why does a motor or compressor need a capacitor to run properly? What actually does a capacitor do?
  32. Problem: My air conditioning unit blows the circuit breaker after it runs for a while. What could be the problem? (With one DIY Youtube video)
  33. Problem: How do I wire up a dual capacitor that I purchased from you? (With one DIY YouTube Video)
  34. Problem: Outdoor fan will start briefly but the compressor does not. Circuit breaker trips in a second. (With one DIY YouTube Video)
  35. Problem: I changed out my control board and my furnace blower motor continues to run constantly. (With one DIY YouTube video)
  36. Problem: My 24 volt transformer continues to burn up. This is the second transformer. What could be the problem? (With one DIY YouTube video)
  37. Problem: How do I wire up my new thermostat? What do the wire colors mean? (With two DIY YouTube videos)
  38. Problem: My AC heat pump unit makes a humming noise even when it is not running? (With two DIY YouTube videos)
  39. Problem: Please help me understand what this warning means on my AC? (With one DIY YouTube videos)
  40. Problem: Will a compressor super boost help start my AC powered by a generator? (With one DIY YouTube video)
  41. Problem: I pulled the high voltage disconnect on my outdoor unit. Why am I still getting a low humming sound?
  42. Problem: Why is water leaking on my floor with the air conditioner on? My service man says I need a new evaporator coil. (With two DIY YouTube videos)
  43. Problem: What could be causing my indoor coil to freeze up? (With one DIY YouTube video)
  44. Problem: Why does my furnace air conditioner have poor air flow? (With one DIY YouTube video)
  45. Tricks for removing a condensing unit fan blade (With one DIY YouTube video)
  46. Problem: Will a larger blower motor help my air conditioning? My air conditioner does not seem to be blowing very hard. (With one DIY YouTube video)
  47. Problem: My Air conditioner’s contactor will not engage. I am not getting 24 volts to the contactor to make it engage? What could be the problem? (With one DIY YouTube video)
  48. Problem: Why I am not getting 24 volts to the contactor? Where does the 24 volts come from? (With one DYI YouTube video)
  49. Problem: What to look for when a capacitor is bad? My unit will not do anything! (With one DYI YouTube video)
  50. Question: Is air conditioner condensate water safe for my plants?
  51. Problem: My Carrier AC unit is cutting off and on. What could be the cause of this?
  52. Problem: Loose Insulation mats inside blower compartment are causing our AC to freeze up?
  53. Problem: Outdoor heat pump unit makes a loud sound in the winter? What is this noise? (With one YouTube Video)
  54. Question: What is the control inside my heat pump that adjusts from 0 to 45?
  55. Question: Are there some recommended parts that should be replaced on a 10+ years old Trane heat pump unit?
  56. Question: What outdoor temperature is safe to test and turn my air conditioner on for the first time before summer?
  57. Problem: Air handler leaking water in the attic on to ceiling! (With one YouTube Video)
  58. Question: Is it best to turn off the heat pump and go into emergency heat when real cold outside?
  59. Problem: Why does my air conditioner condenser fan motor burn up so often?
  60. Problem: The fuse on my control board blows constantly. How do I find where the short is?

24 thoughts on “Air Conditioning & Heat Pump troubleshooting questions with answers index

  1. I have a Goettl, roof-mounted heat pump. Recently the blower motor/fan destroyed themselves. I took the blower unit in and had the motor/fan replaced but upon installing the unit, it will not function. No heat is produced and the blower does not come on. I am a fairly handy person but there are so many different switches and relays I feel like I am chasing my tail. Can you offer any guidance?

    1. Hi Sean! I am very sorry, but I do not know anything about Goettl roof-mounted heat pumps. If I was trying to troubleshoot your unit I would start at the fan motor and trace the wires back to the control that starts the fan motor. I would check voltages at this control and see if 220 to 245 volts were being sent to the fan motor when the thermostat is calling for cooling. If the power is going into the control and not going out to the fan motor then this is where the problem is. Sorry that I can not be more help. This is what I found when I Googled the subject on troubleshooting Goettl heat pumps: https://www.google.com/search?q=Goettl%2C+roof-mounted+heat+pump+troubleshooting&rlz=1C1ASUM_enUS497US497&oq=Goettl%2C+roof-mounted+heat+pump+troubleshooting&aqs=chrome..69i57.6696j0j8&sourceid=chrome&ie=UTF-8 I hope you can easily find and fix the problem. Steve

  2. I just had a heat pump installed in my home. There are seperate inside units for upstairs and downstairs. The intake fans for both units draw air from the house 24/7, even when there is no need for heat to be produced (like when heat is set at 60 and room temperature is 70). Is this normal?

    1. Hi Clyde! No sir, this is not normal. You should be able to set your thermostats on “Fan Auto” and the indoor blower fans should cycle off and on with the need for heat or cooling. I would suggest calling the company who installed the heat pumps and explain your problem. I hope you can get this taken care of because I know your home probably feels drafty with the fans running all the time. Steve

  3. I have a Trane heat pump TWG model – it cools fine – when the fan engages inside it tries to start, tries again (up to 8 times) before it actually engages and runs – my AC friend says motor may be going? I thought relay? any ideas? you can imagine it sounds like someone manually turning on and off a (fan) several times before leaving it alone to actually run… I’m concerned about fire hazards and excess power usage.

    1. Hi Suz! I would suggest that you check the blower motor run capacitor to make sure it is in good shape first. More than likely you will need a new motor. I would also like to suggest that you test the voltage going to the motor. If you are getting a constant 210 to 245 volts AC coming from the control board or relay to the blower motor and the motor is still going off and on then it is a blower motor problem. If the voltage is going up and down then you probably have a control board or fan relay problem. If you have a thermostat with batteries please make sure the batteries are in good condition. The thermostat through the green “G” connection controls the fan motor. If you want me to look up parts then please send me your air handler’s model number. I hope you can easily find and fix the problem. Steve

  4. I have a Carrier Puron and am having trouble with cooling. We set the temp to 68 in the summer but the heatpump will only cool to 77 then go up to 78. What could be causing this?

    1. Hi Keith!
      Most of the time when an air conditioner does not cool properly it is caused by the unit being low on refrigerant charge. I would suggest that you get a tech out to check the charge in your system. Dirty filters, a slow blower motor (make sure capacitor is good) and a dirty condensing unit can all cause poor cooling. I hope you can easily find and fix the problem. Steve

  5. I had a Luxaire 3 ton unit installed in August of 2014. Immediately in the heating season the unit would turn on in heat mode but immediately (after 3-5 minutes) switch to auxiliary heat (ie: electric backup). This is suburban Philadelphia, but this problem was occurring even in mild external temps (ie: +40 degrees). I called the installation contractor and the distributor but got not satisfaction until the summer of 2015 when the Distributor Rep and the Installation guy showed up, spent about 1.5 hours at the house and said that maybe it was the thermostat. I questioned this as the installation included a new thermostat. Well fast forward another 6 months and another astronomically expensive heating season. I continued complaining and finally got a second visit from the Distributor and the contractor. Another 1.5 hour diagnostics at the house and they concluded that nothing was wrong. That maybe the unit was quickly switching to aux heat due to it being undersized for the house. Huh ? they had recommended the 3 ton unit for my 2500 sf. I then started seeing news of wide spread TVX valve problems through out the industry. Never once did the contractor or the Distributor Rep mention this as a potential problem. Does the problem I am having suggest a TVX problem ? A/C works fine . Just heating.

    1. Hi Tom! I would not recommend a heat pump this far north in Philadelphia because of the many days that you have below 30 degrees in the winter time. No, this problem should not occur with temperatures above 40 degrees. I would agree that a 3 ton unit on a 2500 square foot home is a little small unless you have real good insulation and windows. The contractor should have performed a heat gain, heat loss calculation on your home before installing the heat pump. A heat loss, heat gain calculation is required by code enforcement here in Kentucky before a permit will be issued. Most of the time aux heat is controlled by the thermostat. If you have a real good thermostat you should be able to control the temperature difference that the 2nd stage aux heat kicks by doing some thermostat adjustments. Some of the cheaper thermostats are set to switch to aux heat by run time. My daughter had one that was set to switch to aux heat if after 10 minutes of run time in heat pump mode the heat pump mode does not satisfy the need for heat. After 10 minutes both heat pump and aux (electric heat) kick in. Yes, some manufacturers have been having problems with TXV valves. I would think this would affect the system in both heating and cooling mode. Attaching and reading the gauges in heating mode during the winter time would be able to tell you if the TXV is working properly in the heating mode. I would suggest that when you have mild temperatures 40 or above that you disconnect the W2 wire (aux heat wire) at the thermostat and see if your heat pump can maintain your set thermostat temperature by using the heat pump only. This would tell you if you have a thermostat problem or a heat pump problem. A good contractor who knows how to troubleshoot heat pumps should be able to quickly see if you have a problem or not. I hope you can find and fix the problem easily and inexpensively.

  6. I have a goodman heatpump splitsystem mod. no. msg18hrn1w problem: heat works good in auto but when you drop temp to cool the inside unit runs but the outside stops both fan and compressor Its a small unit the evaporator is mounted on inside wall for a sun room

    1. I tried to answer you through your email address, but it would not work. I wanted to send you a parts list. I am sorry, but I am not familiar with the goodman mini split system units so it would be a guess as to what the problem is. This could be a thermostat problem or a control board problem. I am sorry that I can not advise you how to troubleshoot this. I would suggest that you call someone who is familiar with Goodman mini-split systems. Steve

  7. Morning my heat pump when I put my heat pump on cool heat come on

    1. Hi Brenton! This sounds like you have a stuck reversing valve, a stuck sequencer which is turning on the electric aux heat or a thermostat that is malfunctioning. A shorted thermostat wire can cause this problem also. I would suggest that you call a tech in to troubleshoot and find out what the problem is. Steve

  8. Hello and thank you for this very informative site to provide information to those with HVAC problems.

    We have a York Affinity heat pump that has had the identical problem at the commencement of the past two winters — one electrical lead connected to the inside heating coil has overheated and on the first occasion had burned off the connector. This involved replacement of the heating coil relay and when that did not completely resolve the problem, the control board was also replaced as it was felt by the technican that one of the two relays on the circuit board were at fault. The pump did work throughout the winter but the auxilary heat and/or emergency heat did not seem to function properly at times but we made it through without anymore expensive repairs.

    Yesterday the same thing happened. The unmistakable smell of overheated/burned electrical insulation permeated the house and all power was shut down on the unit. Once again the identical lead insulation was melted two inches back from the connection on the small heating coil relay and the relay’s plastic housing around the wire connection point was melted and deformed. It is obvious too much amperage was drawn and the circuit breaker did not trip however.

    I was fortunate to have two technicians attend and they worked for several hours to repair the existing wiring and replace the relay. This work did not solve the problem as things commenced to heat up once again on testing the unit.

    The company owner visited today and completely rewired all existing circuits from the thermostat to the control circuit board and double-checked all wiring connections. Several hours later, the breakers were thrown and after a few minutes, the electrical odour commenced once again. All are at a loss to explain why the circuit is drawing an overload and they are conferring with York to ascertain if their wiring schematics are correct for this unit and thermostat.

    In the meantime, could it be the circuit breaker itself located on the front panel. I think the initial failure may have damaged internal contacts or whatever inside the breaker which in turn may be causing the failure even if the electrical wiring connections are top notch. Much more if this and I’ll be bankrupt. Winter is just getting underway here.

    Thanks for any advice re: this trouble.

    1. Hi David! I am very sorry to hear that your are having all these problems with your York Affinity furnace! I always attribute any wire burning to arcing or loose connections in the air handler or furnace. Yes, you are correct in believing that the breaker with pitted contacts can cause heat, high amperage draw and burn out other connections in the furnace. I would suggest that you listen and feel the outside of the breaker when the electric heat is on. Many times I could actually hear (in a quiet house) the breaker arcing on the inside and feel the breaker getting warm on the outside. I hope by replacing the breaker and making sure all connections are good and tight that this will eliminate your problem. Thank you so much for posting this! Maybe we have an electrician or other HVAC tech who can comment and help solve this problem. Steve

  9. Been using MERV 4 synthetic filters in my Goodman system and they never got dirty. Changed them every other month just as a matter of habit, but now my evaporator coil has to be cleaned or replaced. A/C service technician says the evaporator coil was dirty because of dirty filters, but yet they were never dirty and changed regularly. Are the filters just too low efficiency to block out the dust that collected on the coil and should I upgrade to pleated filters?

    1. Hi Bob!
      I would suggest upgrading to at least a merv 8 filter. Yes, pleated filters should be much better. I would also recommend that you check to make sure air can not by-pass the filter and go up into your furnace without being filtered air. Thank you so much for asking this question. Steve

  10. i bought a new coleman control board for my heat pump in the fan is only running for 3 min than cut off

    1. Hi Deena!
      If the condenser, outdoor fan only runs for 3 minutes and cuts off then I would first look to see if the contactor is staying engaged/energized or not. If the contactor is engaged and the fan cuts off then you probably either have a weak fan motor capacitor or a fan motor that is going out. When the motor cuts off I would suggest turning off the power to your unit then lightly touching the fan motor to see if it is hot. If the motor is hot then you might either have a weak capacitor or a bearing or winding in the motor that is going out. Best of luck in finding and fixing the problem. Steve

  11. Have a goodman heat pump the inside unit has stopped working could drain be backed up and float switch have it shut off I haven’t been to diagnose just trying to figure out what could cause it any other ideas other the blower motor burnt up

    1. Hi Dustin! Yes, if you have a condensate pump with a safety switch then this could cause your heat pump to cut off. I would suggest that you use the following air conditioner, heat pump flow chart to trouble shoot your problem: https://arnoldservice.com/wp-content/uploads/2014/12/air-conditioner-troubleshooting1.pdf I hope you can easily find and fix the problem. Steve

  12. We have a lennox air conditioning heat pump. I have just replaced start up capitor. The fan outside and inside will kick on but the compressor won’t in gaged. Unless I go out and water the unit down and then it will kick on. It will run sometimes for 3 hours and then kick off and come right back on in about 10 minutes. At that point sometimes the compressor will come on by itself. I will run normal at night. This only happens during the day. Can you please help. I’m tired of calling repair company to come out and they 20 minutes and it’s never fix. Thank you

    1. Hi!

      Good morning! Sorry to hear you are having trouble with your AC unit! This sounds like a high pressure or over-heating problem because you said that after you water the unit down it will kick on. Here is a link to one of our pages that discuss the high pressure problem: https://arnoldservice.com/problem-my-outdoor-air-conditioning-units-high-pressure-switch-trips-ever-so-often-why-does-it-high-pressure-switch-trip-so-often/ Your unit might be dirty of over-charged with refrigerant. The company that came out should have cleaned your coil and checked your unit’s refrigerant charge. An over-charge of refrigerant or an under-charge can cause a unit to act as you are describing. The next time your unit shuts off like this, please turn the power off to the unit and lightly touch the top of the compressor to see if it is hot. If it is hot then you have a low or high refrigerant problem and this needs to be corrected. Also another cause would be if the outdoor fan kicks off in the middle of a cycle this will cause the compressor to over-heat and the high pressure switch to trip thus causing the unit to shut off and not come on until the pressure is reduced by watering down the unit. If your outdoor condenser fan seems to be running slow or shuts off during a cycle you will need to get this fixed. Best of luck in finding and fixing the problem. We have lots of troubleshooting advice on the following page: https://arnoldservice.com/troubleshooting/ I hope you have a great day!
      Steve Arnold, https://arnoldservice.com

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