Updated October 13, 2026
School Double Doors Stopped Closing After an AC Change: LCN 4040XP Door Closers, Aventura
A school in Aventura emailed me about three sets of double doors that wouldn’t close all the way. The doors had been fine until the AC was modified, and the extra air pressure was holding them open. I replaced all six closers with LCN 4040XP units, set them to 8.5 lbs of opening force, and the doors close every time.
What the email said
They wrote, “Hey, we have an issue with 3 double doors that won’t close all the way. When can you guys come out and do some adjustment on these doors?”
I scheduled it for the end of that same day, because a school can’t leave its doors open overnight. I got there at 3 p.m., after the kids finished school.
What I found
I watched how each door swung. In the last 15 degrees, the closer couldn’t push the door shut. When I put my hand in the small gap, I could feel the air from the AC pushing against the door.
I tried making the closer spring stronger and adjusting it, but all six doors acted the same. That told me the closers weren’t strong enough to close the doors against the pressure.
Ruling out the hinges and the frame
I checked the hinges, then turned off the AC, and the door closed right away. A door that won’t close can point to a hinge or frame issue, but not here, because six doors stopped self closing at the same time. In large rooms, it’s very common for the AC to push too much air into the room.
So I asked the facility manager if they had recently changed the AC pressure. The answer was, “You know what, you’re right. The issue started the day after the AC was modified.”
Choosing the closers
We both agreed on a stronger closer with higher tension, and for this kind of application the LCN 4040XP is the winner. I replaced all six closers on the three double doors and set each one at the door with a gauge to 8.5 lbs of opening force, the figure Florida uses for exterior doors. That’s strong enough to close and latch against the air pressure, and light enough for a student to open.
I also explained to the school what had changed, so they know a future AC adjustment can affect the doors again.
The work
The job took three and a half hours, including the assessment, removing the old closers, installing and adjusting the new ones, and cleaning up. We always leave the site clean after an installation.
Before I left, the facility manager walked all the exterior doors with me to check that they were self closing properly. Besides these three double doors, everything was in great condition.
What was on the invoice
Only the six new LCN closers and the installation. My pricing is upfront, and you approve it before I start.
What a real locksmith knows
I tell customers that every door is different, and we need to fit the best product for each application. When there’s an air pressure issue, I always go with the bigger LCN model, so it lasts a long time and has the strength to force the door closed against the pressure. I also check the door frame and the door alignment, because they can cause the same problem.
The local angle
Aventura is in Miami-Dade. Large rooms like the ones in this school get a lot of air from the AC, and when that pressure changes, it shows up first at the exterior doors.
Exterior door not closing all the way since the AC was changed? Call Around The Lock at (954) 371-5674.
