Where is the port on a 1988 Chevy Suburban R10 so you can refill the freon and what kind of freon do you use?
This is not a simple repair, as it is illegal to add refrigerant without repairing the leak. If you are not qualified to perform this repair, take it to an expert. It is definitely not a novice weekend mechanic repair. However, you can buy leak detector kits to first determine why it needs recharged. This could be a leaking seal at a line joint, a bad line, a seal in the compressor, or a pinhole leak in either the evaporator or condenser. (If I already lost you - go no further - have it done for you.) The other problem is that your refrigerant system will have originally been an R-12 type Freon which is now no longer available. To repair a leak problem means the additional complication of conversion to a legal R-134 type refrigerant. Adding a different type of hydrocarbon coolant such as "DuraCool" also may not be legal. If you have the gauges, and the required know-how, you can do this. The big question is whether this amount of work is justified on a 20-year-old vehicle.