When you say "Full Blast", does the blower spin on high? Do you mean the temp doesn't get hot?
As for your thermostat, if it's stuck closed, you'd quickly overheat. If it's stuck open, it would take a very long time for the engine to reach normal temps.
Also, check the heater control valve at the firewall. If all of these things are good, then you'll have to remove the HVAC unit for inspection. You may have a stuck blend door or leaking vacuum hose/solenoid.
Tuesday, November 30th, 2010 AT 12:20 AM