Half way let's outside air into the heater box so you have air flow to the feet or windshield as you move and gives the fan air flow so it can blow properly. This also helps keep a soft top inflated so it doesn't flap so much.
All the way out is the fresh air vent that opens by the passenger side feet and another flap up under for the drivers side feet. This bypasses the heater core area.
The heater control is a bypass flap. Coolant always flows through the core, the heat control just says how much fresh air either goes through the core or bypasses it to just blow outside air in when the air knob is half way.
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com
(10 new albums added Sept 16/10)