there's a red little lever on the center tunnel right in front of the shifter.
that's your heater lever!
the 3 knobs on the dash control how fresh/hot air is distributed.
- the top lever is for the fresh air fan (pray that it works), and moves fresh air only!
lever to the left means no fan, lever to the right means fan speed 1-2-3
- the middle lever is for directing air, either hot or cold.
lever to the left means all air goes down to the foot-area.
lever to the right, all air goes to the windshield (and sidewindow-vents if the car is '73 or later)
- lower lever is for how much hot air you want in the car.
lever to the left, no hot air. lever to the right, sauna.
disclaimer: hot air is only available if the heater boxes are not rusted shut and the cables haven't been ripped into pieces (cause the boxes were rusted shut) and the hoses are still attached and not ripped, both from the heater-boxes to the longs as well as inside the engine bay. it also helps a lot if your car is equipped with a additional air-fan in the engine-comp that funnels air through your heat-exchangers!
have fun with your car
Andy