bottom flap on heater box

October 24, 2006, 01:44:45 PM

I have a problem with the flap on the bottom of the heater box not sealing off the cold outside air. All my heater selections work fine. After getting to normal operating temp, i get a cold draft from the heater box. This is coming from the flap on the bottom of the heater box. This flap is on the inside of the box. To the best of my knowledge, the has to be vacuum pulled to open this flap. I have not checked to see if I'm pulling vacuum to this flap with the heater selection on defrost. Does any one have any ideas on what may be the problem?