1971 heater levers positioning

[Ferrolanoman]

My 4 heater/vent levers on the upper dash above the radio move smoothly back and forth but I am at a loss as to how they should be positioned for: a) heating and, b) for fresh outside air. Additionally, there's a round knob to the right of the levers, with a blue mark resembling a semicircular water drop, that turns clockwise and functions--I'm guessing here--like a rheostat turning on an invisible fan that's labelled DEFROST. Is this the sole source of forced heater and/or air?
I'll be much indebted if someone can tell me exactly where each of the four levers should point (extreme right, extreme left) for Heat and, then, for outside Air. Also when the fan works for either/both.
Thank you respondents and a Merry Christmas to all.
Ricardo

[thelews]

Do you have an owner's manual?

[doitwright]

You should have red and blue arrows on the chrome trim where the levers protrude. This is an indicator of the lever function and the range of air volume from maximum to closed.

Top left is blue. Lever positioned to far left is wide open to regulate incoming outside air. To the right is closed. This lever operates the damper in the fresh air scoop in front of the windshield.

Top right is gray. (Unless it was replaced with an aftermarket orange) This lever controls where the air is distributed. Defrost or directed toward feet areas or a little to both

The 2 bottom levers are red and control left and right heat supplied to the cabin. The left lever(on left hand drive cars), controls a damper above the blower fan that permits heated air to to be fan forced to the defrost and foot areas. This lever also controls the valve to the heater core via a linkage between the damper and heater core.

The right red lever permits heat to be distributed on the right side of the vehicle.

Interestingly, the round chrome vents on the right and left side of the dash only supply fresh air when the blue lever is open. They may also allow return air to the blower when heating with the fresh air damper closed.

The knob to the right of the controls is your blower fan speed control.

You can search this topic on this site and will find numerous discussions, photos and diagrams.

I hope this helps.

[Norm]

Same info as posted by doitwright but phrased a little different.. 

Look at the wedges. 

The large end of each wedge is the maximum for that lever, the pointed end is the minimum

Blue is fresh air (more / less) air comes from the vent in front of the windshield

red is heat / temperature (more / less) heat comes from opening the vents that control air flow over the heat exchanger and opens the valve to allow coolant to the heat exchanger.  Both the heat exchanger and the vents are not visible but located behind the dash controls.

the arrows directs air "up" to defrost "down" to cabin (in between is mixed defrost / cabin)

Yes the knob on the right controls the fan.  All the way clockwise is maximum fan speed (the air flows to where you have the lever adjusted by the lever with the arrows.

If all of this still doesn't compute, have someone drive the car while you adjust the levers to see what effect each control has.

have fun..... 

Norm

[Garry]

Have a read of our Technical Manual as well!

[Ferrolanoman]

Thank you Frank and Norm, your clear and detailed explanation/instructions are all I needed. As far as the owners manual being helpful, I'm not sure I agree. And the BBB is probably needlessly complicated. I do own both books plus a lot more M-B publications but nothing as readily understandable as the two responses provided above.