I HAVE AN 08 PONTIAC GRAND PRIX V6 AND THE HEATER ISNT HEATING PROPERLY. IT BLOWS COOL AND THEN WARM AND BACK TO COOL, I'M NOT SURE IF I NEED TO BURP IT OR CHANGE THE THERMOSTAT
Sounds like your cooling system is not full. May be air trapped in the system, or it may simply be low. Make sure it is full. Putting a new thermostat in as well can't hurt. They're inexpensive and they don't last forever.
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