Any other cause for Heat /Cold Mixing in cabin than Heater Valves?

I replaced these about five months ago brand new from BMW. I had bypassed the core for a few months but the Valves were in the flow still. I reconnected everything yesterday. Today went for a long drive with the ac on the first half of the drive . later turned on the heat full for a half hour and when i turned the AC back on i got a Mix... just wondering if i F'ed up some duct of venting or forgot a plug though all the functions respond as normal to the controls. I thought i remembered reading there is designed in a small amount of warm air from the dash vent closest to the driver at all times but not enough to overcome the Max AC which it is now.... Where's that Heater valve refurbish page is that on gale's page? :D