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Mini split making noise

Hello to all

I recently installed a Fujitsu heat pump. The system works fine but the customer complains it makes a very slight but audible noise coming from a/h. To me it seems to make a crackling noise, in either heat or cooling, like copper expanding or contracting. With system off and fan on it makes no noise. Any suggestions?

Thanks mike.


  • don_9
    don_9 Member Posts: 395

    Sound like the blower motor,they had a recall on certain model years ago that the motor had bad brearing.The reason you are not hearing it in fan only is bc the motor is at a lower rpm.Been there done that.
  • charliechicago
    charliechicago Member Posts: 124
    I don't hear the noise

    Even on high speed? Thanks for the reply.
  • don_9
    don_9 Member Posts: 395
    Fan only

    Yes but if I recall fan only is not high speed it is a very low speed.The unit will not ramp up to high speed unless there is a call for heat or cool.Just saying that has been our experience with noise issue.

    The only other thing it could be which I doubt is, velocity noise with not using the recommended length on your line-set.My money on the blower.Happy hunting.
  • BRW
    BRW Member Posts: 1
    Defrost Cycle

    I have had a Fujitsu Heat pump for about 5 years now. When it goes into defrost the indoor motor shuts off and condenser runs in A/C mode to defrost the outdoor coil. This creates a crackling noise. Its normal when the unit is in defrost.
  • Techman
    Techman Member Posts: 2,144
    Line set

    How long is the line set, then I'll tell you if I agree w/ don ,or not!
  • charliechicago
    charliechicago Member Posts: 124
    The line set

    Is 25 feet long. This is 24 feet less than the max length and above the minimal. In regard to the fan speed, when in high speed the blower does turn very fast. The customer seems to only hear it in heating mode. Fugitsu had me make sure the charge was right, which was. They also had me ohm the txv which was fine. Any help would be greatly appreciated as the customer is not too happy

    PS. I spoke to a friend of mine asking for advice. He made me feel better about my situation. He installed a fugitsu 3 years ago and if I remember correctly every time the AH comes on for about three or four minutes it spits out water. I don't recall what he tried to fix it but he was unable to solve the problem. Any suggestions would be appreciated as well.

    Thanks, mike.
  • NYplumber
    NYplumber Member Posts: 503

    Are the line sets insulated and strapped all the way to the unit so that the two copper tubes wont chatter?

    Are the two lines insulated individually or together in one bundle?

    How about the drain and the wiring, are they insulated or strapped properly?
  • Buster
    Buster Member Posts: 30
    Agree with BRW

    About the Defrost, also the unit keeps the fan off or very slow until it gets HOT for comfort. The sounds are expansion noises similar to baseboard for a comparison.
  • charliechicago
    charliechicago Member Posts: 124
    I don't think

    It's vibrating. The pipes are individuall insulated. I don't hear anything outside by the lineset. It just seems to be the copper expanding and contracting. It also makes the noise when it shuts down, like a car engine. Thanks for your responses. Mike
  • pamsebec
    pamsebec Member Posts: 1
    I have 2 Fujitsu mini splits 12k on one 24k outdoor unit.,the living room unit is quiet it's about 46 feet from the outdoor pump. My bedroom unit is about 10 feet from the outdoor pump and is noisy whenever living room unit is the only unit "on" I heard refrigerant moving and cycling. So I shut the LR unit off and use my LP boiler. yr 2 . trying to use both indoor units, the bedroom one still hisses no matter if on or off, and it's fan noise is louder too. I was told that it could be refrigerant pressure due to too short of a line. (sounds like a squirt gun when cycling then vibrates, and hisses later) it is the exact same unit as my living room. I have a 3rd unit in the cellar running off a 2nd pump. It is the older12, so the guy gave me a deal. I got sick of complaining about the noise. I just don't use them. But I want to, oh,my squirt gun noise just went off again, now vibration, perhaps I should run it until it breaks then I can verify that it was bad? I still get noise if I turn it off, and leave the living room unit on...oh I can never win.
  • Jack
    Jack Member Posts: 1,045
    I have a dual 24, a 12 and 15 in the house. All are quiet regardless of phase of operation. Is the mounting bracket secured at the lower corners? I had a slight buzz on the 15 I added after our re-model and fixed it by adding a toggle bolt at the lower corners of the mounting bracket and making sure the cover was securely mounted.
  • radmix
    radmix Member Posts: 194
    crackling noise will happen in heat mode because the line sets and the entire unit is heating up and expanding. It should only do this on start up then subside when the unit is running in what I will call steady state.
  • Big Ed_4
    Big Ed_4 Member Posts: 1,746
    Hmm strange , maybe the evaporator coil is not sitting right in its pocket... I would pull the cover and take a look
    I have enough experience to know , that I dont know it all