I have a 84 300 CD Turbo Diesel

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The RPM guage is not working at all

Besides the Guage itself what are the components I should check that may be broken that would cause the RPM Guage to not work

Thanks

 

Mine was a broken wire on the passenger side wheel well, going to a set of enclosed grounds. Looked like it had been chewed through... walnut shells on the rail next to it.

The only point here is that all other gauges worked correctly. But that single ground kept the tach from working. One possibility, although improbable.

 

check the round connector on the drivers side fender well with the screw-off top
my friend put in 1/8 inch shim tomake the connection tighter

 

Did you try the cigarette butt trick yet? It takes one minute and has solved the problem for many. I bought my 82 300TD three weeks ago and tried it. I was shocked that it worked and it hasn't stopped working yet. Take a clean cigarette butt, unscrew the tack amp cover place the butt in the middle of the prongs and screw the cap down again. Somehow the upward pressure of the filter piece against the screw down pressure of the cap causes the contacts to touch at a different location. It is worth a shot if you haven't tried it already.