I posted this in "Diesel discussion" with no avail

Ok got an 85 300 D with a non functioning tach. Here is what I have done so far:

1) I have tried another gauge with the same results.
2) Checked the EGR relay fuse and its good
3) Replaced the tach pick up in the bellhousing with a new one
4) The 85 Models DON'T have the tach amp on the fender, so that does not apply
5) Looked for anything obviously wrong with wiring, nothing.
6) All other gauges work just fine

On this year model if the tach does not work, then the klima relay won't engage the A/C compressor, which of course it does not.

What am I missing??

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
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