heating and cooling issue now its cold

[expo dude]

i have noticed that my truck wouldn't heat up well in defrost mode nor bi level mode and also i have noticed that the compressor is running non stop in these modes when i run the panel mode or the floor only mode the vehicle seems to heat up better and the compressor isnt running non stop. i thought in defrost mode the compressor was supposed to run for a but then stop for a bit am i incorrect? this truck has a ne w water pump new tstat flushed system and heats up good if that compressor isnt running it also has rear heat and air when the compressor is on the heat from the back almost goes away being luke warm some info would be great thanks

 

[Bedrck47]

would help to know the model and year in order to give you better information

Having a signature line always helps

 

[expo dude]

its a 99 expedition 5.4l 236000 miles4X4

 

[Bedrck47]

does it have manual or EATC controls

 

[expo dude]

It has the manual cc also I did change the door when I changed the heater core.

 

[expo dude]

could i have a low flow situation the heater cores have both been replaced the water pump has been replaced full flush on the truck still heat is bad in the cabin if i turn the heat off let the truck run it will blow hot after i turn the heater back on but moments later it will blow cold.

 

[stamp11127]

Check the flow in and out of the core.