You can look at the iFixit guide link in my signature to find a step by step on accessing and replacing the OVP relay fuse. It was the cause of my dead tach on my '85. The 1985 model year has a unique setup for the tach vs. 1984 and earlier cars.

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

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