Nissan Repair: at idle no heat, 2002 nissan altima, water temp control

Question
Hi Von i have a 2002 nissan altima 2.5s no heat at idle driving at speed the faster the hotter the air gets. changed out the thermostat, no change, i looked on line said it could be water temp control valve, i dont know what it looks like,or where its at or how to test it,any help appreciated,thanks

Answer
Steve,

Look on the firewall, behind the engine, there will be two heater hoses.  One is the one that lets hot water into the cabin and the other one allows it to return to the engine.  With the car at operating temperature, feel the hoses.  One will be hotter than the other one.  That is the one that lets hot water go into the cabin.  If there is a valve, I cannot remember seeing one on an Altima, it will be on this hose.  Of there is no valve then the heater core is probably obstructed.  You can verify this by having the heat on and feeling the hoses.  The other hose should get warm too.  If it is substantially colder than the one that feeds hot water in the cabin means there is a restriction like a plugged heater core.    You can remove the hoses and using a water hose from the house, you can feed water through one hose and see if the water comes out unobstructed.  If there is no obstruction then you need to follow the hoses to the engine and see what else could cause an obstruction.  If the water does not flow means the heater core is plugged.  Let me know if you need more.