Sometimes our cars, appliances, and even air conditioners make the strangest noises, but how do you know if they’re normal or if something might be wrong? It’s not always as easy as hitting the ‘restart’ button on your computer, so it’s important to know when you should call a professional or contractor to check it out. The following are some tips about what sounds are normal and what indicates professional problem when it comes to your air conditioning unit. Outdoor unit noise is normal upon start-up and shut down.  The outdoor unit is where most of the mechanical operations in your system take place and depending on the type of equipment, it can be noisy and somewhat varied when it starts up and/or shuts down.  Typically, most air conditioners make noise when they first cycle on, which can be caused by the buildup of pressure in the refrigerant lines or from bearings, fans or other moving pieces starting up.  The same is true when the unit cycles off, or comes to a stop, as the pressures need to equalize.   

Sometimes this causes a unique noise that sounds like air escaping, a click or rattle. : If the start-up and shut down sounds are the same from cycle to cycle and not too loud, it’s probably normal and not worth calling a contractor. Outdoor unit running noise after start-up can also vary among different types of equipment.  Once the outdoor unit starts up, it should reach a consistent sound where you hear the fan blowing and the other mechanical parts humming along.  honeywell ac unit says waitSometimes you might hear a cycling sound over the period of a few seconds where the unit changes the pitch of its normal running sound and might get louder or quieter in “waves.”  ac control unit for mitsubishi lancerIf it gets increasingly louder as the system is running, then it might require a contractor to see whether it is out of balance or requires further inspection.  auto repair in mcallen tx

If you hear a loud, intermittent mechanical “scraping” or “banging” noise, this is not normal and you should shut your system down and call a contractor to inspect it as soon as possible. : Significant changes in pitch or ‘banging’ noises indicate you should call a contractor. Indoor unit sound is usually the sound of the fan moving air through your system.  It is most noticeable when the system turns on and off. If you have a high efficiency system (16 SEER and over) you could hear two distinct sounds as your system moves from high to low cooling speed.  The high speed sound can be noticeable, but the low might be so quiet you can barely hear it. : Air moving through your system should sound smooth and consistent once it is running. In general, sound is a subjective attribute and the above descriptions are provided as a guideline for noises that could potentially signal a costly problem.  In addition, we have recorded some typical compressor sounds you might hear during a normal start up, run and shut down cycle as examples.

Sounds like the ones you will hear in this audio file are typical examples of what you might hear during normal operation in a healthy system.The requested URL /phpBB3/viewtopic.php?t=23692 was not found on this server.Reader QuestionHello Austin,I am new to your site, but have enjoyed getting a chance to read your answers to many common car problems. I am writing to you about a perplexing noise I am getting in my 2000 Avalon. It has 127,000 but has been maintained very well from day one and runs like a dream. Just recently I started hearing a noise behind the dashboard. It sounds as if it is coming from directly behind the steering wheel. It sounds like grinding gears or like something is scraping against something else inside there.I almost blamed it on the tape deck at first since it resembled a tape being stuck or stripped in the deck but I ruled that out by turning off the radio and the sound continued. It has nothing to do with speed or the steering mechanism itself. I almost think that I have it pinned down to being related to the AC somehow but I am not certain that is it.

It does not happen all the time and generally increases in volume when the auto AC is trying to adjust to a really low setting. When I turn off the AC when I hear the sound, withing two minutes or so it stops. The sound is only coming out of the dash on the drivers side as well. It is not audible from outside the car. I am really stumped as to what may be causing the noise and have never pulled the dash out on this car and am hesitant to do so. Do you have any ideas on what this might be? Stephen M.Howdy Stephen, Wow, you got me stumped. The only thing that really comes to mind that might be able to cause the noise you describe would be the A/C blower motor, which is inside the dash…..kinda more towards the passenger side than driver side but its about the only thing that is rotating inside the dashboard.The blower motor has a hamster wheel attached to the end to push the air into the cab. This wheel could be loose or rubbing on something? Taking the dash apart is not going to be easy or cheap.

If you wanted to guess at something you might want to have your mechanic check into the blower motor/blower motor wheel “cage” and see if there is a problem there.Wish I could help more, keep me posted if you dont mind. I would like to post your fix on the site for others.Thank you for your response Austin! This problem has stumped me and my mechanic friends for the past 4 months. The problem is that half of the people I tell about it never hear the sound because it is not an every day thing. I cannot tell exactly what sets it off so it may go four or five days and make no noise at all and then poof one day it is doing it on and off all day. I decided to take a video of it so you might be able to hear it for yourself. I had to wait a few days for the sound to come back, but it did and I pulled into a parking lot, shut off the radio, and the ac and recorded this.Any new thoughts on what this may be???Thank you so much!!!post #1 of 317 (permalink) Heater blower motor repair I decided to post this little tutorial so others don't go through the frustration I did tonight.

Recently there have been several posts about heater blower motor failures. I joined those ranks last week. My blower was operating intermittently, and when it did work, I had to have it on high to get any air movement at all. I call my local smart center, and a new motor is $287!:eek: Some have had switch failure, and some have had the resistor burn out. I traced my to the motor itself. I could wiggle the wires going into it, and change the speed of the motor. First off, after wasting 1 1/2 hours trying to figure out how to pull the heater assembly, I finally figured out it takes 2 minutes to pull the motor. Below, see the motor locaton on the heater assembly: Next is a picture with the blower removed: remove the connector, and simply turn the motor assembly counter-clockwise until it releases. Then pull it out. Here is a picture of the motor out: Remove the torx screw on the end, and you can pull the motor and fan wheel out of the plastic housing: When I pulled the motor, the commutator was completely black.