HVAC Issue-Help Needed

[Sluggo0018]

Hopefully someone with more knowledge of central air conditioning can help with my situation.

The system has been working fine this cooling season, until now. When leaving the house this morning, I noticed a humming noise coming from the outside compressor of my first floor central air conditioning system. The condenser fan was not spinning and I thought that the noise might have been from a seized fan motor. But the fan rotated freely when I nudged it with a stick.

The humming noise was quite low in volume. Periodically, it would get louder for a few seconds, then return to the lower volume for 20-30 seconds before cycling to the higher volume again. During this time, the interior blower motor was running, but the condenser fan was not spinning. I turned the system off and left for my meeting. When I returned roughly 5 hours later, I tried the ac again via the thermostat and got the same results. Low humming with short intervals of louder humming.

The compressor unit is a Goodman model CLT 30. It has been in service for 16 years. I have a photo of the info plate if that will be of any assistance. The second floor compressor is also a Goodman (slightly smaller) and is currently operating well.

Can anyone offer any guidance for trouble shooting this system? I am generally pretty good at diagnosing and fixing things, but this is a little outside of my comfort zone. I do not have any refrigerant system manifold pressure gauges, but I do have a multi meter if there are any electrical tests that I should run. My initial guess is that the compressor is seized up for some reason. This could be refrigerant related, or it may simply have worn out. Also, I have noticed this season that when the compressor activates the noise seems to be louder than in past years. I didn't think much of it at the time, but the issues may be related. Cooling wise, I haven't noted any difference this year from previous years.

I would appreciate any assistance that you can provide.

 

[rekit]

Cond. fan relay or fan. When the fan doesn't run the compressor builds up high pressure and a sensor should be shutting the compressor off. Then it cycles again and again.

https://inspectapedia.com/aircond/HVAC_Condenser_Fan.php

 

[bullwinkle]

Likely either the contactor failed, or a wire burnt off it. If you turn off the circuit breaker, pull the disconnect, and remove the junction box cover, it'll probably be obvious. The buzzing noise is the energized 24V contactor coil. If the compressor was locked up, it would likely trip the breaker or open a cartridge fuse in the disconnect.

 

[kkreit01]

My parents recently had a similar problem. The fix ended up being the relay. The cap and fuse were also bad, but that didn't fix the problem. The techs could tell the motor got real hot, and may go out at any time. This was 1 month ago. It's still cooling today.

 

[Donald]

Check if the fan motor is getting any juice when it should be running.

 

[sloinker]

Capacitor/contactor/motor.

 

[Sluggo0018]

Thanks for all of the suggestions. I will go outside and check it out. Right now it is pouring rain so it might be a little while.

I will let you know what it was, or come back with more questions.

 

[mk378]

Likely it has a dual capacitor for the compressor and the fan and both sections are failed. The noise getting louder is the compressor trying to start then cycling off on the overload protector.

 

[Greggy_D]

Another vote for the capacitor.

 

[LeakySeals]

I just went through this 2 weeks ago. My post is here. I learned a lot about it. It was really hot out and all of a sudden I had no AC. Went outside to the central air unit and the compressor was hot but the fan wasn't turning. makes sense without the fan you can't cool the refrigerant. And you can't cool the compressor either which is a bad thing. So the test for capacitor was to spin the fan manually like an airplane. If it takes off it's the capacitor. If you get nothing it might be the switch next to it. See my post for pictures

 

[EA82]

If neither the fan or the compressor are running I would check for the capacitor first, see if it is a dual capacitor and is swollen.

 

[zzyzzx]

Capacitor or contactor.

 

[wag123]

+6 on the capacitor. In my experience 16 years is over twice as long as they generally last, but since you live in NJ it will last considerably longer then it will in Texas. You might not be able to tell by looking at it that it is bad. They are under $20, just go ahead and replace it. Get one with the identical MFD specs (but you can uprate to a higher voltage). If you hear humming, the odds are 98% that it is not the contactor.

 

[spasm3]

Look at the capacitor, if its bulging, replace it, but yes they can be bad and not bulge.