L4600 heater problems

[urd505]

I have an L4200 heater won't heat,I've replaced the thermostat,didn't help...

 

[KennyV]

is the water valve in the heater hose open?

 

[urd505]

I checked,it don't have a valve where the hoses connect

 

[pedalstomper78]

Few things that we need to look at here.

First off, is the engine getting up to normal operating temp? What's your temp gauge say?
Once things are warm, see if you're getting any water through to the heater core. AKA, check to see if those lines get warm.
If the fan blowing? You may also need to look at the damper door to see if it is directing air through the heater core.