2002 Rio Heat not working properly

[letsjump]

The heat only seams to work when i am accelerating. When sitting at a stop light or low in a gear, it blows cooler air. When I get up into the 2000-3000 RPM, it starts to blow warmer.
When trying to defrost windows--cold air only, no heat.
Please help.
Thanks

[dsolorio]

Check the water lines, they could be clogged with something like stop leak. disconnect them and use the water hose to flush the core our then do it in reverse.

[m_wnzl]

check your coolant level

[ronjohn]

Some good ideas here letsjump. Also if you rev it up and it get's warmer maybe a water pump/belt issue what is your temp gauge reading about half way? http://www.kiatechinfo.com/ for service materials. and also check your cable for hot and cold setting good luck