last night i was up driving around Alta, UT in about 1.5 ft of fresh
snow...yes it is mid june.  and i got a bit stuck.  i pulled my diff
lock knob, while stationary and in neutral.  then i put it in first and
tried to pull out.  drivers left and rear passenger (right only, i
think) wheels spun---no locked rear diff and no green indicator light.
it has worked in the past, but this is the first time in a while that
i've needed it.

recently there was a thread about diff lock problems, fixing and or
diagnosing.  i searched the archives from 1 june to 16 june on diff or
differential, but didn't come up with exactly what i was looking for...

what is the proper way to diagnose the problem with my diff lock,
starting with most likely first, since it has worked nicely in the past.

thanks,
fred