glove box latch repair

[fordmerc]

glove box latch doesn't work - pushing the button does not open the latch, nor does the button have any spring resistance. I have removed the unit and can remove the lock cylinder, but I can't figure out what is wrong. The only spring is between the latch "arm" and the base of the unit. A diagram or a description of how it is supposed to work might help. I don't see anything broken, but I don't know what to look for. (My local "locksmith" was of no help) ('41 120)

Advice appreciated