Weird HVAC Issue

[BadFord]

I have searched quite extensively and not found this issue here. I had to replace my Blower Motor Controller and did so with the aftermarket harness upgrade. Since doing this (a couple of weeks ago) I have had this happen twice... with my HVAC turned OFF completely, it still blows air. Not out the vents, but it seems to be behind the dash. The fan switch does nothing, the OFF button shuts off the head display, but no change in air. And the AUTO button changes nothing with the air either. The only way I have found to turn it off, is the turn the car off. Then it's fine. Anything from the experts?

[SilverPhoenix]

Have you done a self test to see if there are any codes?

[RubberCtyRauder]

Check your vacuum lines. The black box on driver fender under hood is the vacuum reservoir. Vac lines get old and brittle over time. Also the eatc O rings get dry and hard and then will only blow out the defrost

[fastblackmerc]

What is the manufacturer of the BCM? You should only use a Motorcraft replacement as all others are crap.

Why did you need to upgrade the BCM harness? I've never seen one go "bad".

[Chi Stallion]

Check the vacuum lines behind the dash. I had that same issue, I thought it was the blend door actuator, ended up replacing it with oem but Zack had discovered a crack in the vacuum line which was causing air not to come out the vents and I believe that's what caused air to come out the defrost while the eatc was off. Already had the eatc o rings fixed too at the time.

[BadFord]

The problem is, it blows with ac head turned off. When it’s turned on, it blows correctly.