Outside unit turns on/off repeatedly

[namiam]

Hello, I'm new to this forum and am hoping to learn a lot of useful information!

I got my HVAC system for my house replaced a 2 years ago, a Lennox 16-seer system (I don't remember the model numbers off the top of my head). Last night I was sleeping and I hear some odd tone coming from my outside unit and wondered what it could be. The tone can be described as: a high pitch sound gradually getting lower and lower over a 3-second span, make sense? This tone sounds like the fan is slowing down and eventually stopping. A few minutes later I hear it again somehow thought it couldn't be the outside unit of my heat pump, because hot air was still blowing out in the house. A few minutes later, again and again all night. Occasionally, it would "sound" like it was normal because it would not shut on/off repeatedly.

Maybe I haven't noticed it until now, but is this normal? I don't want to call a tech over if this is normal behavior of a typical system.

The system (or at least my heater) still works great though.

Thank you.

[makinmoney]

There is nothing wrong with calling a service company out to check the system if you are concerned about it's operation. Better to do it now if there is an issue before it becomes a costly disaster.......

[nomadpeo]

in heat mode, see if there is cold air blowing out of your unit outside. also, feel the copper lines connected. the small line should be slightly warmer than your hand; the larger line should be hot. the exception would be if it is in defrost. defrost occurs when ice is detected on the outside coil. in defrost, the fan should not be running outside and the larger freon line will be cool. if it is in defrost, once the ice is melted off, it should soon return to normal heat operation (first description).

this is a non-technical way to determine if your heat pump is working. whether it is performing properly is something that should definitely be checked by a professional. if your house is warm, it is possible the heat pump is not working and your aux heat is heating your house. if you think something is wrong outside, you should be able to place your thermostat in the 'emergency heat mode' with a switch, which disables your heat pump to prevent possible damage while awaiting service.

some heat pump sounds are normal that do not occur with a regular condensing unit (outside). if you are hearing a new sound, it's worth checking out. my first impression of the sound you described is that you may have a compressor stalling. the other clue there could be a problem is that you notice it isn't cycling on and off at a regular frequency.

good luck.

[namiam]

Thanks, I will take both advice when I get home. I will also take more advice if anyone else has any.

[RyanHughes]

Is it defrosting? Part of what you wrote (high to low pitch noise, fan slowing down) makes it seem like it could be. If it is, it's normal operation for heat pumps.

[namiam]

Good to hear that news Ryan. I'll keep that in mind.

[RyanHughes]

Sorry, after rereading your post -- if this is happening every few minutes, does not sound like it is defrosting (at least the way it should be). Something happening this often should be checked out.

[namiam]

Oh really? How long should it be occurring then?

[dean martin]

Pretty sure Lennox uses a 30 second compressor shutdown going into, and coming out of defrost, so it would be normal to hear some noises. Does the unit seem to be clear of ice, that is defrosting properly?

Your OD fan is shut off during defrost, so that would be normal. Your electric heat is turned on during defrost, so you should be feeling hot air inside while all of this is happening...normally hotter than when it's just running as a pump.

Just average numbers, your defrost cycle might last 2 - 10 minutes depending on how frosted it is. So you'll hear the reversing valve shift, the compressor shutdown, the fan turned off, the compressor come back on for the duration of the defrost, the the compressor turned off again, the reversing valve shifted again, and then the compressor restarted again....there is alot going on and it's all normal stuff.

[martyinlincoln]

Normal to hear that defrost cycle every few hours. Not normal to hear that noise every few minutes over and over again.

[namiam]

So the service guy just left, he said it was normal and the sound I was hearing was the unit defrosting.

However, he went out to check the unit while he was here, and he heard another noise that he thinks MAY be in the compressor. He said the part can range about $1,000 for labor to repair? Totally unexpected, I was expecting about $100. This is a 2 year old unit!!! The service guy said all the pressures and everything look right, just he heard something fishy that may be inside the compressor.

Has anyone had to repair/replace their compressor?

[RyanHughes]

Is the unit defrosting every few minutes or every 30-45 minutes? If it's defrosting every few minutes, certainly not normal.

[namiam]

Is the unit defrosting every few minutes or every 30-45 minutes? If it's defrosting every few minutes, certainly not normal.

Well, it only happened that one night, but after that, it hasn't been doing it every few minutes anymore.

[Texas-Tech]

I'd just let it run. It's under warranty for 3 more years.

[namiam]

I'd just let it run. It's under warranty for 3 more years.

So you recommend repairing before the warranty is up (if this problem gets worse)? I was also thinking of this.

I also have 5 extra years of warranty (Lennox Limited Extended Warranty), parts only, no labor.

[karsthuntr]

So you recommend repairing before the warranty is up (if this problem gets worse)? I was also thinking of this.

I also have 5 extra years of warranty (Lennox Limited Extended Warranty), parts only, no labor.
Let the compressor run until it dies, you have 10 year warranty on the compressor. :)

[Texas-Tech]

For all we know the man may have been jerking you around.

[nomadpeo]

compressors usually fail in a solid manner and those problems can be detected with proper testing. capacitors, start relay, reversing valve, defrost components and metering devices are associated components that can fail as well. most of the time, these components fail in a solid manner as well. using the term 'fishy' to describe a compressor problem and throwing a $1000 ball park price indicates to me that either complete testing has not been performed or the problem is intermitent and the tech could not detect it. if it is related to a defrost problem, it could have been missed if there was not a call for defrost. how long was he there and what was the temperature outside at the time ? his description of 'fishy' could be a way of saying he could not catch it in the act. since you have indicated that the problem seems to have gone away for now, that is probably the case.

[Ricky Dale]

Your defrost board may have an issue which hasn't totally failed.