08 sentra no cold air after oil change and fluid top off

Going by what you are saying I do not see anything that they did that would cause your A.C to go out. It is just one of those things that happens sometimes when you are getting other work done. Have A.C system checked out to see if it is low on refrigerant.

Is their anything special about charging the Nissan's A/C.... The low side pressure was too high and so no coolant could be added. Now I have someone telling me I need a new compressor. All I saw done was that they tried to start the compressor directly from the battery.... but isn't there a switch involved for the A/C to start ? I really can't afford a new compressor already !!

Ty for the previous answer btw...

I would check the fuse for the A/C first before saying it needs a compressor.

To test the compressor remove the connector from the high pressure switch then get a paper clip that will fit snug into prong on connector once you find the right size paper clip reshape paper clip into a u shape then stick paper clip into the prongs of the connector then start vehicle and turn on A.C. Compressor should start working if not check fuse. Once you confirm that the compressor is working remove paper clip and connect back to switch if compressor does not come on take a hammer and lightly tap on switch if compressor comes on replace switch because it is sticking if it does not come on replace switch because like I said most of the time that works by tapping on switch but not all the time and it is still bad. To replace switch is simple unscrew switch ( no freon will come out ) screw new one in and connect the connector back on switch and that should do it.