Here's a strange heater problem. I get cold air from vents when i have heater on to 90 degrees is my rpm is below 2000. When I accelerate and get rpm above 2000 for any period of time i get heat. Whats going on? my first thought was the water pump going bad? Thermostat seems to be ok. There is no overheating. I also replaced the climate control unit because the fan was acting funny.

Thanks for any advice.