2002 Mitsubishi no heat

Open the hood, you should see a plastic recovery bottle under there somwhere. Make sure it's filled to the proper hot or cold line. Open this bottle only after the engine is cool, the antifreeze is under pressure, and you can get burned!
If filling the bottle does not get the heat working, try checking the heater core, heres how.
Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working!