Hi! I have a 5 ton central air AC unit (just AC, no heat). It seems to operate normally (it cools the house, starts and stops according to thermostat, etc.). Every time it starts, it operates with a strange noises for a few seconds and the noises is gone and at the end of each cycle, when it turns itself off or if I turn it off, the compressor makes a strange noise for about 10 seconds as it stops. It's a high pitch squeal that starts loud and quickly drops in intensity (just like a balloon letting air out except that the noise is more "metallic" and sounds like metal parts rubbing together...like an old door with rusted hinges. My ac was working fine until i found the wires from the fan motor were hanging loose and the fan blade was touching them. I called the company that installed my ac unit to take a look at it ( the ac units is only 8 months old and it has a warranty of 2 years). The Tech fixed the wires and notice the unit was a little bit undercharged so he added more refrigerant since then i start noticing a noice when the unit starts and when unit ends a cycle. A technitian will come to take a look at the unit again in 3 days (unit has been runing with this problem for 2 weeks), do you know what i could be the problem? do you think that the tech damaged something in the compressor by adding more refrigerant? what should i do to make sure this problem will not affect the unit in the future? my warranty will be gone in 16 months.
Thanks

 

Its never good when a comp makes noises like you say, I would shut it down until the tech comes out. You may want to call the Service Mng of installing co. and request they send there lead tech out.