AC cab air inlet

[69SCSS]

Quick question... I have an AC cab and I have used the AC Delete outer box so that I have just the heater. While I had serious issues fitting their product and would not recommend it, I figured it out a long time ago and it works fine. Except... there is no way to stop passive airflow now thru the heater core and into the cab.

From what the shop manual says, the AC box can draw from inside or from the cowl, with a vacuum servo opening and closing the flap. As far as I can tell this is true, but I can't be 100% sure, and I'm still getting some passive airflow into the cab.

Anyone shed some light on this? It's not that much of a problem right now as it's barely in the 60's here now, but in the later spring / summer it's gonna kinda suck.

There is still the diverter in the inner box, but that just stops the air flowing into the heater portion, the air is still in the box and seeps out. This helps a little but it still gets warm in the cab!