Not warming up?

This is my 2nd mazda, and both when I first got them would not get warm at all, my current mazda doesnt even go past the first line on the guage. My last mazda I replaced the thermostat but it still wouldnt get too warm. Anybody else ever have this problem, Im guessin its the thermostat but just making sure. Any input would be great thanks.

Especially during the colder months of the year our Bs have a hard time warming up because the cooling system can be a bit too efficient at times. This happened when I was much younger riding in the back seat as a 7 year old. The truck was running poorly in Pittsburgh snow (riding from Atlanta for xmas) so Dad had to get a piece of cardboard from a West Virginia McDonalds and blocked off half of the radiator.

Now the diagnostic questions. The temp senders in these things are garbage, 2 out of 3 are inaccurate. Does your upper and lower radiator hose feel warm at all after driving? Do you get any heat out of the heater core? Does your fan clutch disengage like it should when it's cold? Multiple things can happen here.

#1 is that your truck is perfectly fine and it's too cold for conditions
#2 is that your fan clutch is stuck in the lock position and this is keeping your fan cooling even when the radiator is cold.
#3 is that your truck is perfectly fine and your temp sender is garbage
#4 is that your heater core diverter valve is clogged or broken, or the linkage is, and that your temp sender is also garbage.
#5 is that your carb is icing up and it's taking longer for it to warm up.