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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53468
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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My 1987 420 sel speedometer and tachometer are not working.

Customer Question

My 1987 420 sel speedometer and tachometer are not working. This means the odometer is not working either i believe. I last drove the car 5 years ago and the speedometer was working. I don't remember if the tachometer was working then or not. All other
guages are working. I have checked the fuses and they seem fine. Is there perhaps a relay not functioning?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.
Hi, there is no relay in the system. Fuse #6 powers the speedometer and the tach. I'd replace fuse 6 with a new fuse and see if it works. Also replace fuse #2. If replacing the fuses does not fix the problem I'd say that the problem is in the instrument cluster circuit board or with the wiring to the cluster or both gauges have failed.
Let me know if you have any questions.