You have three controls. A switch that controls the fan (off--1--2), a slider that controls the heater matrix valve (red triangle--blue triangle) and a slider that controls where the air is blown (white symbols).
The trick to remember is that the two outer vents (by the doors) are not heated - they go straight to the scuttle area under the windscreen. If it is cold, close them and you will notice a big difference.
On most X1/9s though the heater valve tends to get stuck, or worse still the control cable comes out. The valve is (on RHD) under the dashboard by your left leg. I used to just reach down and flick the valve open/shut with my thumb - at least I knew it was working that way.
jimbro - I think you have confused the red and blue sliders! There are four sliders in total (counting the fan switch).
The red slider - move toward the thick end of the arrow - heater matrix water flow 'on'.
The blue slider - move toward the thick end of the arrow - airflow through heater 'on'. I believe it's like an Uno - if the blue slider is 'off', you don't get any airflow through the heater (so, no hot or cold air).
In my experience it's the blue slider control that tends to break - but this is no great problem if it's broken in the 'full airflow' position.
Oh NO - I've just realised that all of this holds true for my '88 Bertone (and any 1500 with horizontal sliders) but with the 1300 the sliders are vertical and hence more like plane throttles. So - you are right all along? Or maybe there is an 'airflow' slider as I've described?
On my 128 Coupe (from the same era, of course) the blue slider controlled cold air entry into the heater. The cold air had to be 'off' in order for the heated air (red slider) to be effective. Perhaps this is how the 1300 works? As you can imagine, switching to an Uno or 1500 X1/9 is very confusing initially, as you turn the blue slider 'off' and lose all heated air...
Darn-it, now I have to go and find a car to look at. Been too blasted long since I drove an X1/9 that actually had a heater matrix (or dashboard for that matter)! Will be dismantling my scrap X1/9 tomorrow anyway so I will take a look (for my own sanity).
Got a sinking feeling you are 100% right though. The hot and cold controls are independent (top is direction, middle is cold flow, bottom is heater valve).