Recently the driver-side temperature control on my HVAC stopped working. Itís all hot, all the time; doesn't matter where you spin it to. Then a few days later, it started working again, and has been intermittent ever since (mostly NOT working).

Soon after that first event, the rear defroster button quit lighting up (and the defroster was not working). Now it, too, is intermittent and mostly NOT working.

Could these two problems be caused by the same failing component in the HVAC system? Trying to figure out what the component might be, what it would cost, and whether I could replace it myself. Thanks.