Sorry, Firefox uses the "last used" printer as the "default printer" for Firefox. There is no setting in Firefox to change that to using the system default, and I haven't seen an add-on that would that either.

I really, really wish Firefox would change this, but I did find one thing.

In about:config I set: print.print_printer to null print.save_print_settings to false

Now it seems to use the system default. And it doesn't remember any changes with in a session, or from one session to the next. It always uses the system default printer.

I realize different people have different preferences. But on my system the default printer changes automatically depending on what wireless network I'm on at the moment. I wanted Firefox to reflect that.

I'm glad you found a solution for your unique situation.

As far as Mozilla changing that or fixing it, I wouldn't hold my breath waiting for that to happen. Most of the printing core code in Firefox is from before Mozilla even existed, from the days of the first few versions of Netscape in the mid 90's. I don't think there are any developers around who fully understand the code well enough to fix it efficiently or without creating other problems. In those days there weren't even USB printers available, much less wireless network printers.

I've waited over 8 years (since Phoenix 0.4) for a few Bugs to be fixed. Bugs related to Firefox only printing the first, or first and last page of a multi page document. Last fall those Bugs were finally fixed on the trunk 4.0betas, but now in 4.0b12 a regression has appeared.

IMHO, Mozilla needs to write a completely new printing core code package, that properly supports the current state-of-art hardware.