A/C unit question

[dante2]

We have a Luxaire outdoor unit that is making a rattling noise on startup during high heat days. It is extremely intermittent, did it about 30 minutes ago and the last time was early August. We shut off the unit as soon as we hear it and let it sit for a few minutes. It works properly after restarting. The noise is down low and not coming from the fan. The unit is over 19 years old and I have replaced the capacitor and the fan last year.
I believe the compressor is slowly failing at this point. We have a couple more days of hot weather then it looks like fall temps after that. Should we be looking at replacing this unit next spring?

 

[WildBill]

I would make sure it's not just metal rattling, I have to tighten the sheet metal screws on mine every once and awhile. Mine also started getting noisy on startup and eventually all the time when it was low on refrigerant.

 

[dante2]

I will check on the screws. Going to get my 608 cert in the next couple of months so I can check into the refrigerant as well.

 

[fitter30]

Compressors have two set vibration springs and or rubber. Most have rubber feet and internal in the shell compressor is sitting on springs. Broken spring compressor will rest on the shell make a loud noise (very rare). But constant.

 

[Wrench97]

Check for ice on the lines at the compressor.

 

[dante2]

As far as I can recall the rattling only happens when the unit is working the hardest during the heat of the day.
Lines are cold but not frozen.

 

[chinboys]

Defective or dirty electrical contactor? Spray electrical contact cleaner into the unit with an electrical disconnect.
Look for pitting or electrical arcing burns too.
Make sure the 24V AC control wires are secured to the two sides of the contactor.
Measure the 24V AC to make sure you are getting such from your thermostat and from the low voltage transformer (110V to 24 V AC)

 

[Jim greengo]

Luxaire/York compressors are normally on the loud side from what I remember.

 

[PWC Repair]

Does it also rattle/knock on shutdown?

 

[dante2]

Does it also rattle/knock on shutdown?

No but it does shut down as soon as the thermostat is turned to off.

 

[PWC Repair]

When a compressor is experiencing mechanical failure they will also knock and rattle on shutdown. Of course there are exceptions to anything. I would try a good quality hard start kit on the compressor and see what happens. A good version will cost $60 or more. It sounds like maybe it's just old and weak and having some trouble restarting after being heat soaked.

 

[dante2]

When a compressor is experiencing mechanical failure they will also knock and rattle on shutdown. Of course there are exceptions to anything. I would try a good quality hard start kit on the compressor and see what happens. A good version will cost $60 or more. It sounds like maybe it's just old and weak and having some trouble restarting after being heat soaked.

Thank you I will check that out. What brand hard start would you recommend?

 

[bonneyman]

Thank you I will check that out. What brand hard start would you recommend?

I preferred the start kits with separate capacitor and switching relay, like the KS-1. But that's for 3.5 - 5 ton compressors.

https://www.supplyhouse.com/Rectorseal-96506-KS1-KickStart-Potential-Relay-and-Start-Capacitor?utm_source=google_ad&utm_medium=Shopping&utm_campaign=Shopping_X_HVAC_X_SSC_ClassA&gad_source=5

But the Supco's with the relay and cap integrated into one compact unit sometimes is better for really tight compartments.

https://www.amazon.com/SPP6-Capacitor-Increase-Starting-Torque/dp/B0002YTLFE?tag=atomicindus08-20