Here is a quick diagnostic on your heater core. Locate the heater hoses that run to the firewall (to the heater core). With the engine warm and running and the temp setting on you heater to full heat. Feel both hoses to the heater core, if they are both warm and feel close to the same temp (one may be slightly cooler) the coolant is flowing though the heater core. If this is the case the temp door in the heater box is not operating and you will have to determine if it is a control issue or or a problem inside the heater case itself. The door may be broken or something fell down through the duct work and is blocking in the cold air position to name a couple of possibilities.
If they are not warm or one in dramatically colder than the other, the coolant is not flowing through the heater core. If this is the case you may be able to flush the heater core out and restore the heat or you may have to replace the heater core.
Just a couple of ideas, let me know what you find and we can go from there.
Thursday, February 25th, 2010 AT 12:46 AM