I used to know this, but can't remember at this moment.
On the cylinder head there are two sending units: one with a red collar (smaller diameter) and one with a green collar (larger diameter).

What are these?

Thanks,

AL

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03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio