This is wierd i notice the other day when I honk my horn the tach moves the harder i push the horn the higher the tach goes the same with just hardly pushing it how do i fix this????? I have a 1983 mercedes 300d turbo.

Aberrant instrument behaviour can have many causes, but a common theme is lack of a thorough electrical ground. Not knowing your model, (hint: always include model in post) a generic way to check is to remove the instrument panel and look straight ahead, behind the IP. There will be three? screws holding a bunch of brown (brown is always ground) wires with ring connectors on them. Remove these and clean the metal contact to insure proper grounding. Make sure all connections to the IP are secure when replacing it. Good luck.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

My crystal ball tells me that he has an 83 300 D turbo.........
William Rogers........