4 Wheel Drive/SUVs: Heat Rav4

Question
My friend just purchased a 2006 Toyota Rav4 with 75,000 miles on it. It is four wheel drive and has a four cylinder engine. The problem is there is very little heat coming out of it. I have replaced the thermostat twice and still get very little heat from it. Do you have any ideas? Also are these plug in portable heaters any good?

Thanks for your help!

Answer
Al,
The thermostat controls the engine block temperature.  It sounds like you may have a plugged heater core, or a bad heater control valve.  I would get a good radiator flush chemical, and flush out the radiator to see if you can clear up any blockage.  Make sure that the heater is on full heat when you do this.
Carl