How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Michael Your Own Question
Michael, Customer Service
Category: Appliance
Satisfied Customers: 9568
Experience:  I have been an appliance repair tech for over 30 years and will help you solve your problems.
Type Your Appliance Question Here...
Michael is online now

B2200 air conditioner system whistling when AC switched on.

This answer was rated:

B2200 air conditioner system whistling when AC switched on. When DC is on without the AC no problem
I suspect a capacitor but which one.
the unit works and cools OK but this noise is there when it is stationery

Hi , I am Tech Michael an expert in this field and I will be assisting you today. I am a Master Technician that's dedicated to giving you the best Answer possible.

If you are new to the site, this is briefly how it works:

1. We may need some back and forth to exchange information (if needed) and there is no extra cost for replying.

2. I will give you the best possible Answer for your problem without the ability of actually being present with you.

The better you describe the problem

, the quicker I can help ;-)

3. Remember to leave a Positive Rating ,it doesn't cost anything additional to rate kindly;-)

I am only credited for my time and expertise if you rate kindly.

How old is your AC unit?

Also does it sound like the whistling is coming from the fan Blower.

Thank you

Tech Michael

Customer: replied 1 year ago.
The unit is 2008the fan is not running when the sound arrives infact nouthing is running and the unit is in standby.If it is started up via the remote it works well and the sound can still be heard over the air con normal noiseIf the DC is on no noise it is only when the AC is on. I am an electrical engineer and the high pitched noise is not mechanical
no fans compressors or evaporators are running.John

Thank you for that information. Yes it may very well be the motor start capacitor or a relay on the control board making that sound. You will need to open this one up to be sure which part is causing this sound.

Usually The start cap near the motor is the fault, but I have heard that from electronic coils and failing relays.

Once you identify the squealing part, I can help you locate a replacement for it.

In any case, I will stick with you until this is complete.

Please rate my service kindly.

Also it is the only way I am credited for my time and expertise with you.

Once you rate, I will be notified and will add your question to my priority list so you can reach me anytime until this problem is solved.

Then you can reach me by simply replying to this message anytime.

Thank you


Tech Michael

Customer: replied 1 year ago.
HiI have located the whistle. It iscomming from the internal temperature sensor board . A new one was fitted about 4 weeks ago
and the unit ran Ok. I diagnosed the fault from the flasing lights.What on this board could whistle. There must be a speaker somewhere to indicate the remote is being usedJohn

Hi, if the whistle is pretty loud it may be coming from a tiny peizo element used as a warning buzzer.

But this sound could really be coming from a failed coil,or a transformer etc.

If that board was just replaced then it seems it is defective and needs replacing once again. It shoudl still be fully covered under the warranty.

If not you could locate that whistling part and replace it if you have good electronic soldering skills. But I would return that board or have the tech who replaced it bring you a new one;-)

Please rate kindly at this time so I can remain with you.

Thank you John.

Tech Michael

Michael and other Appliance Specialists are ready to help you
Customer: replied 1 year ago.
HiI know its this board as I have taken it out in the last 10 mins and fly wired it back into the system. As the unit is hanging in the air as I move it the noise moves with it.I have never used this site before and will try to rate as requestedJohn

Hi thanks John, that worked.

I suspect that board, but who replaced it and why?

Customer: replied 1 year ago.
HiI am a controls engineer and I am used to fault finding on large systems. The manual only has two indicator functions for fault and I had a single flashing light which suggested the internal temperature sensor as stated in the manual.I spoke to Dometic who gave me the part number and I changedThe fault went away but has just been replaced with this whistle.John

I see, was the whistle present as soon as you changed out the board?

Or did it develop sometime later?

Thanks John.

Tech Mike

Customer: replied 1 year ago.
MikeIt came about a week after the change The problem is I am a little deaf and my wife noticed it last week on holiday
I can hear it with my hearing aids in.Is the remote receiver electronics on this small board as I cannot see a decoder or receiver chip. It mat be the main board signaling the small board.John

Thanks John, yes thats possible but usually what ever board is making the sound thats the one with trouble. Also make sure you dont see that little peizo buzzer f there is one on the board. If not, Its probably just a defective board as you would be surprised how many parts I replace that defective right out of the box lol.

Tech Mike

Customer: replied 1 year ago.
HiNot sure what you mean by a pezio buzzer.Johnson

That would be a buzzer PBC mounted for a warning but I don't believe yours has one on the board fro that.

Yours dies have one that will chirp when you turn it on normally.

You simply have a defective new board is all.

Customer: replied 1 year ago.
Hiyes no warning sounder but it does chirp when the remote is used and the sounder is on the replaced board. I will request a replacment.Many thanks John

Sounds good John, let me know what happens when you replace the board again.

Thank you and have a great weekend!

Tech Michael

Customer: replied 1 year ago.
Hiboard changed but the chirper still whistles. I put my finger over the chirper and it is this that is making the noiseI took the batteries out of the remote to make sure it was not giving a signal but the problem goes onthere is only one board left in the system and that is the relay boardJohn