How do you check the coolant level on a 2002 buick rendezvous?
There are marks on the side of the coolant reservoir that indicates the proper level. Keep it filled at all times if you are losing coolant you may have a leaking hose or may be your Lower intake gasket. you should not ever have to add coolant to your system.
If the low coolant light is on after adding coolant will this affect anything else or should you just keep a check on the fluid level?
If you are talking about a vehicle, then the coolant level is critical for generating heat. Check you vehicle coolant reservoir if it is empty, wait until the engine is cool and check the level of coolant in the radiator and fill as recommended with the appropriate kind of coolant then fill the reservoir to the level indicated.