... very common.
you have to remove the entire housing, drill out the broken bolt/s, and replace them, or replace the entire housing with a good one from a parts yard.
cruddy design. the thin bolts get moisture on them, corrode, and fail. MASSIVE soaking with penetrant is advised prior to service.

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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 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!