99exp
Member
New guy here, nice to be aboard. Having issues with the heat in my 99 expedition w/ dial teperature control knobs. My problem is I get decent heat on the floor however when I switch to defrost it gets cool pretty fast. This is what I've done so far: 1 changed the thermostat, 2 cut peep hole in plenum and the blend door operates as intended, closing heater core off when temp. dial in cold position and swinging fully open in the hot position. I can touch the heater core and it's hot so I don't suspect the heater core is clogged., I do feel quite a bit of cold air in the plemun. Question, is the there a fresh air make up damper that could be open so I'm heating external air and not cabin air?? Running out of ideas. The only damper I can see is above the blower motor and it moves toward the firewall when I turn the flow direction dial and swings back in the off position (towards the cabin) Any input would be much appreciated
