In the process of refurbishing our flapper boxes (AKA Flap Control Box Heat exchanger), one of the springs broke and fell out. I see no way to replace it. Is this box junk now?
Click to view attachment
I assume that best case, it will not close completely. Worst case, it binds and gets stuck open.

It opens and closes OK on the bench, but if I go through the full throw of the arm, the lip of one of the sealing plates can catch and get stuck. When installed on the car, will this actuate from stop to stop or just the mid range?

Ugh!

I have a couple of 914/6 flappers that failed the same way. I don’t have an easy fix to post but will watch to see what other might have done.

In my case I’m keeping the /6 flappers with the idea that maybe someday I’ll split them open and repair them but to be honest it looks like a lot of work just to have an original /6 flapper.

Of course /4 flappers will work just the same but if you’re going councours it might cost ya’.

I have ground off the rivet head that holds the flaps together and replaced the spring from a box that was in worst shape. I used a 4mm bolt with nyloc bolt the reassemble.

Now that an idea worth considering - thanks! I knew someone would have ideas on this.

The beauty of this forum

No doubt.

Interesting! Did you disassemble the halves of the box to make it easier to replace the springs? If so, how did you get it apart without destroying it?