My grand Caravan blows warm air only in front when driving, replaced thermostat, water pump, reverse flushed heater core and radiator cap.

What is your question?

2010 grand caravan 4.0 quit blowing hot air in idle, blows hot in front only while driving or 3000 RPM, replaced thermostat, water pump, reverse flushed front and rear heater cores and replaced radiator cap. I read somewhere to check the heater control valve but I can’t find it. Is there a valve and what else could cause no heat.

What makes this problem better or worse?

Running at higher RPM