I just did a test where I grounded a wire and then jumped both wires together. This was on the sensor. I was wondering how do I read the sight glass if I can't start the A/C. Both times the A/C compresor started in the test. Which said Low Refigerent.

 

You need to get a volt meter. Check the continuity between the two pins on the a/c pressure switch. If there is continuity, then your refrigerant is low, or your switch is bad.

You cannot determine the a/c system pressure of refrigerant level by looking at the sight glass. You need to get a set of low/high gauges and measure.

 

Evacuate and recharge the system. Diagnose the leak.

 

Check your AC valves. I had refrigerant replaced and it was gone in a few weeks. discovered one of the ac valves was leaking.