where is 93 honda civic heater core and valve located?
 

My heater is blowing only cold air. The tempurature guage looks ok and running at normal temp so I don't think it is thermostat. Could this be the heater core or valve causing this? If so where exactly is this heater core? What about the valve? Does anyone know where I can find pics or step by step instructions showing this location or how to replace/check either?