My wife and I have a lennox heat pump and started noticing last year that along with the normal noise you hear while it is runnig you can hear a slight pulsating noise from the unit. I had the service tech come out and he said it was normal that lennox's tend to make a little noise. Last night it was cold enough that the unit actually had to go into defrost mode. When this happened you could hear the pulsating noise a little more clearly since the fan is not running during defrost. The nosie seems to be coming from the area where the capaciter is, but hard to tell. Any ideas on why might be causing this so I can mention it to the tech when they come out to the winter service? Other than the noise the unit works fine

 

Is this the outdoor condenser unit???? Did they put any freon in when they where there.????

ED

 

Thanks for the reply. Yes this is an outdoor unit. They didnt add any freon to the unit. When they came out to do the seasonal maintenance they said the charge was fine.