strange heater and temp gauge issue

[stephenm2682]

my probs started last october, my first fault was all ignition lights came on when i was driving home, the alternator clutch pulley was clicking away, the problem seemed to have gone when i got home, but now i seem to have a temp gauge issue, as i can be driving and all of a sudden it shows no reading etc, also the heater starts blowing cold air when i want hot which also happens intermittently.

could this all be relating to the battery not getting enough charge or is it something else, like just an air lock as i seem to have an issue with loosing coolant from the expansion tank, it seems to be leaking from the cap and it comes out of the little hole underneath the tank.