This may seem silly to state, however, make sure that you do not have your dimmer switch turned all the way down. You have 5 bulbs in your instrument panel, and highly unlikely that all (5) have blown at the same time so double check your dimmer switch. As for the heat/ac not working, you may need to have your blower motor checked because that may be the cause of your problem.
It is possible the bulbs burnt out. Is it just the speedometer, or is the whole cluster out? Check the dimmer switch, make sure it is on all the way. Also, check the fuses for that circuit. The cluster would/hvac control panel would have to be removed to check the bulbs and wiring. The speedometer bulb should be serviceable. The hvac control panel might not be.
〉 Answered on Nov 11th, 2013 by Helaine Kurot, Owner/Technician at 360 Automotive