In my 99 (and most likely for most years) the design of the Auxiliary Heat-A/C is such that heat only comes out of the integrated floor registers. A/C only comes out of the headlinger vents. When the front function selector is set to FLOOR or MIX, the auxiliary system send air to the floor vents. There is a typo in my manual that states that also in VENT position the auxiliary air is directed to the floor. Mine is directed to the headliner vents (and maybe floor). The manual counters itself in the very next paragraph by stating seperately, in the VENT position, the auxiliary unit will be recirculating interior air to the "discharge registers" (having never defined whether this refers to the floor, headliner or both registers). The front VENT air goes through the blend door so it will pick up heat if you set the temp control to warm. The rear unit has only a damper door to direct air and no blend door to control temp.
Thursday, April 5th, 2012 AT 5:36 AM