For a while now I've been having issues with my blower motor sporadically going on and off while it should be on full blast. Tonight I driving to work and turned off the A/C system and the blower was blowing full blast out the defroster. I shut the car off and the blower motor is still running full steam. I've tried restarting the car, locking it etc. and it won't shut off. I'm sure I'll have a dead battery 8 hours from now when I'm ready to leave work. What would cause an issue such as this?

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2022 Nissan Frontier Pro4x
1990 Mercedes 420SEL
1950 Packard 8

Previous German cars-
2001 Mercedes SL500
1983 Mercedes 300SD
2011 BMW 328i (manual)
2008 BMW 535xi (manual)
2006 BMW M3 (manual)
1980 Mercedes 300TD
2006 BMW 750i
1996 Mercedes E300D
1994 BMW 740i
2006 BMW 330xi (manual)
1999 E300DT Smoke silver/black 253k
2012 BMW 535i Xdrive M-Sport
1984 300TD-T 304k
1988 Mercedes 560SEL (parts car)
2010 BMW 550i xdrive
2017 Audi A4 Presitge
1979 300SD 313k
2003 E500 189k