I need to add freon ton a 1998 suburban. I

Sort of.
If the system is empty, you would need to jumper the low pressure switch to power the ac clutch to put the first can or two of freon in.
Keep in mind the system is supposed to be vacuumed out before adding freon, so if it is full of air you won't be able to put the full amount of gas in.

I WOULD HAVE TO SAY, NOT EASY. ORIFICE TUBE IS LOCATED ON THE REAR QUARTER PANEL INSIDE OF SUBURBAN. THE FREON NEEDS TO BE CAPTURED BY A FREON RECYCLING MACHINE. THEN THERE ARE SOME PANELS THAT NEED TO BE REMOVED TO GAIN ACCESS TO THE H.V.A.C. BOX , THIS IS WHERE YOUR HEATER CORE, EVAPORATOR CORE AND FAN BLOWER ARE HOUSED,THE SMALLER METAL FREON CONTAINS THE ORIFICE TUBE THAT NEED TO BE PULLED OUT. I WOULD STRONGLY SUGGEST TO YOU TO HAVE THE FREON PRESSURES CHECK FIRST, CAUSE WHEN THE FREON IS LOW THE REAR A./C WILL NOT WORK AS GOOD ANYMORE. PRESSURE READING SHOULD BE: LOW SIDE 35-45 P.S.I. AND ON THE HIGH PRESSURE SIDE IT SHOULD READ: 200 - 250 P.S.I.ANYTHING DIFFERENT IF BOTH PRESSURES ARE LOW, JUST ADD SOME FREON VERY SLOWLY UNTIL PRESSURES ARE WITH-IN THOSE RANGES.

The low side is the smaller valve, and if you are using a one hose system to charge it then that fitting will only fit the low side valve which is the small one, good day.

hi.
it is possible for either to be faulty, but it far more likely to need regassing.
there is a pressure switch in the freon system that will prevent the A/C clutch engaging if the pressure is too low.

i would get the refrigerant checked and topped up before starting to worry about anything else.

My ac light is blinking, and the ac compressor clutchpulley is not engageing. Its also blowing hot air

Check the pressure of the low side port when the a/c is running the compressor. It should read 25 psi to 45 psi. If it's too low then it may be leaking out.

Check that the compressor is turning when the a/c is turned on.

You mean a wiring diagram? Blower problem or Compressor doesn't come on? Is it full of freon? Does the compressor come on if you jump the low pressure switch?

The hissing is caused by the freon going through the orifice tube, so do not touch the 2 nuts. You will loose the freon in the system.

What's probably going on is the mode actuator is not functioning correctly.

Take it to a professional, a dealership should be able to help you.

Yes add oil,it is hard to say how much without knowing how much you lost. I would guess 4oz of pag oil. And yse vacuum and charge the same. Find out how much freon to add.

teh low side must to be the closes to the a/c acumulator.