87 non turbo 300D

my tachometer currently isn't working...
i was wondering how the tach gets its signal.
I found the rpm sensor near the flywheel, traced the wire which goes to one big relay, KILMA i think, then goes thru the right side of the firewall where the battery is...

IF i were to completely bypass the wiring from the sensor directly to the tach on the cluster, what needs to be done? can i wire the rpm sensor directly to the cluster? I've read about tach amps with regards to 123 bodies, i think the 124 don't have this anymore, does this mean that i can wire it directly?

knowing the actual path of the current from the sensor to the actual tachometer would help a lot... thanks guys!

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project