troubleshooting a tach?

The tach in my '83 300D is mostly dead. Sometimes it will wake up and the needle will wave wildly for a few seconds. What's the best way to go about troubleshooting this?
Any pointers appreciated....
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The tach amplifier is the likely culprit. The pins get loose solder joints and create an open or intermitent connection. It is a black cylindrical canister about 1 1/2" in dia and about 3" tall located on the left front fender well. The simplest fix is to unscrew the amplifier and place a small wad of papertowel in the center between the pins and screw it back down. This creates a forced contact with the solder joints and the tach should work again. I've had to do this 5 or so times in the last 8 years with my 300SD. Let us know if that works. Doug
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I reread this post and noticed yours is a 300D in which case the amplifier my be in a different spot than my 300SD. Everything else is the same. Doug
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On Tue, 15 Mar 2005 20:07:11 -0800, dougmcp wrote:

Thanks Doug and all. I've made the modification and will see if that works when the repairs are complete......
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Two garden hose washers have worked best for me.
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73
Hank WD5JFR 83 300SD
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No need, it's almost certanily yor tach amp and you can fix it with a small rock or the filter broken off a cigarette.
http://electric.articles.mbz.org/300tachamp /
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