The oil is there for one purpose ,thats to lubricate the compressor ,but it also traveles with the refrigerant through the system and when you have a leak it will be forced out the place where you have the leak ,thus after awhile you will lose some oil ,generaly the leak will be around the seal in the compressor.
The oil used to lubricate the compressor is cycled with the refrigerant.
You need oil in the compressor just as you need oil in your engine. If there is no oil, it will lock up and seize internally. yes it can cause damage to the bearings in the compressor. The unit has oil in it to lube
To lubricate the compressor.
Oil starvation is one possibility. The refrigerant is what transports the compressor oil through the system - an insufficient amount of refrigerant won't properly transport the oil, and it'll starve the compressor of lubricating oil. And insufficient amount of compressor oil in the first place could also be a cause, especially if you're charging a dry system. If you did add oil, did you spill any on the compressor? Because I've seen that cause what you're describing, as well.
The compressor oil
That refrigerant oil
It is essential to take measures to help release refrigerant from the compressor oil during refrigerant recovery when the refrigerant release valve is stuck closed. The release valve should be maintained at all times.
Remove the compressor and pour it in. If its making noise its probably to late and you will need to replace it.
Generally, because something is wrong with it. Maybe a bearing went out, maybe the compressor is just worn, maybe it was damaged because of a refrigerant overcharge, compressor oil overcharge, or the wrong type of compressor oil used. Could be a number of reasons.
You don't need to engage the compressor clutch to recharge the system. In fact, you shouldn't engage it without refrigerant and oil in it, because the refrigerant carries the compressor oil in order to lubricate the compressor. But, to answer your question, you disconnect the low pressure switch, and run a jumper wire between the two female ends of the connector.
Refrigerant should be miscible with lubricating oils to ensure proper lubrication of the compressor components. If the refrigerant and oil are not miscible, it can lead to oil dilution, reduced lubrication efficiency, and potential compressor damage. Miscibility helps to maintain proper lubrication and prevent premature compressor failures.
If there are contaminants in the oil, the system will need to be flushed.