fluid level is not important, at the moment, condition of the fluid is. what color is the fluid? bleed out some fluid from the frozen caliper, and see what it looks like. try putting it in a clear jar, and let it settle, I bet it has a few layers. if it's recently changed fresh, like less than 1 year, then it should be fine. otherwise, flush it all out, and put in fresh. also are the flex hoses cracked up? how old are they? they can deteriorate from the inside and cause a caliper to freeze up.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!