Just a strange question. Why can you turn on the recirculation button when the aircon is on cold, but you cannot do so when you have the heater going?
Not a major problem just curious as one would assume that by recirculating, the air would warm up quicker. Have has some minus 5 mornings lately and it takes a bit of time for the cab to warm up.

You should be able to if the heater isn't on the max setting

You should be able to if the heater isn't on the max setting

that is correct. I find it annoying though that you can't use recirculate when it is set to demister

Thank you JoshSx, I will try it on a lower setting. However like rprodrive says it is with the demister going that I need it to work. Sorry I did not make myself clearer.
The past two weeks we have had massive frosts and -5, -6, -4 etc. Even using (dangerously) warm water to remove the frost, the demister is useless for the first 5 or more minutes, so usually the screen refreezes slightly.
Will try different setting to see if I can get it to work.

that is correct. I find it annoying though that you can't use recirculate when it is set to demister
That is interesting. With the max temp and recirc, maybe it was for heat issues and to prevent drowsiness. On the L/W series 3rd gens, it automatically goes to non-recirc if going to demist (and there is a big difference in temperatures). I then turn it back to recirc.

This morning I sat in a very cold car and tried a few settings.
While on demist and foot settings with the temp set just under max it let me recirculate, as soon as I turn to full demist it turned of recirculate. No matter where I set the temp control it would not let me turn on recirculate.
So looks like I shall have to use the foot/demist setting at a lower temp and freeze for a bit longer.