I have a 1991 ford ranger 2.3L 5 speed. The heater has not worked very well only blowing mildly warm air. I just replaced the hea gasket,water pump,thermostat,heaterhoses,and radiator hoses.Now that I have recently needed the defroster and I am getting no heat at all. I have checked the cable adjustment on the blend door and it's working. Today I removed the heater hoses at the core and blew into the core. On one side I can blow air through and when I blow into the other side there is resistance is this normal? I also tried hooking the hoses up to the opposite ports and still no heat. Any ideas ?