I am having a problem with the lock on my glovebox of my 91 740 sedan. When I turn the knob it doesn't open. I need to know how to get the thing open without ruining my dash or the door of the glovebox.

just pry the thing open, thats what a thief did on my box. barely left a scratch on the trim above too and the lock and door still works fine. don't think its a secure place to lock stuff in. i learned the hard way.
good luck
LC

Thats funny you say about that....this must be a common thing. I ended up pulling the Plastic section above the glove box out to open mine again. Made a mess. so be careful if you decide to try this attempt. I broke some of the trim. fixable though. make sure you have another lock to put in before you bother getting it open. the light will stay on and the door wont stay up.mine is still broke but at least its closed.
The lock is broken, it a piece inside that sheared off.I used JB weld and a dremmill to fix it, but it did not last.
Good luck,
Rich

This is a common problem on 850s, but they have a simple wire loop to hold the latch. The 740 lock looks like Fort Knox by comparison.

I'd try to drill the lock out, then replace the whole thing.

Or ... you could ask a dealer for an estimate, it COULD be inexpensive ;)
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3 8s & 2 7s 740,000 miles total