Ok I see now, just read the good old FSM. The red dot key just was another way of marking the master keys. Ie they open all the locks and shut the alarm off. MB got rid of them awhile ago, now they are just master keys. Cool stuff, I didn't know the guage cluster and brake pedal were also part of the system.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Had the problem with my 86 W201 which has the factory alarm system.
Ended up buying a new door lock into which you insert the key - not the mechanical lock. The unit is very expensive. If you have the factory alarm
you have in front of the fusebox another rectangular box. When remove the cover you will find 2 red fuses there. If you remove those alarm not working anymore. Agree, crappy sytem.