problem with heater on 2003 GMC Sonoma

blower motor works and engine temp gauge is 180 with heat on high cdabin temp gets to about 70 I should be getting roasted out but am not. When you have on defrost or floor heat you can fill air coming out of dash vents. when unit is completely off you can fill air coming out of dash vents.

Asked by for the 2003 GMC Sonoma
2 answers 2 comments
check the coolant level, thermostat and make sure both heater hoses are hot.

Coolant level is fine. Will ckeck hoses. If not hot what does that mean? I have heard that the factory coolant which is Dex-Cool can plug heater core.
You most likely have a bad blend door actuator motor. Roy is correct to make sure both heater hoses at firewall are hot. There's no heater control valve. Heat is controlled by a blend door. Of course there are other things you need to check before you just replace the actuator. Go to and purchase the info for anything concerning your truck for $26.95 for a whole year.
Thank you. I have an appointmoint to get it worked on dec.15th I am trying to narrow down what it could be. Don't want them just replacing parts till they finnaly fix it. Anyone can be a parts replacer. I do have some mechanical background. Again thanks. I checked heater hoses at fire wall they were warm.Upper radiator hose warm lower hose cool. I could leave my hand on all hoses none where to the point where I would say man that's hot.