I pulled the instrument panel and my cruise amp& actuator all at the same time....got the odometer fixed and re-installed the cluster....tach doesn't work.
It worked before just fine. I checked the connection to the tach and all fuses.

QUESTION....is the tach linked to the cruise/amp wiring system? There are a couple of multi-pinned connectors still dangling under the dash that go to the cruise unit. Could this be why the tach doesn't work now?

Thanks

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day

I also have an 83 TD...my tach has never worked. I suspect my amp was ripped-off before I rescued the car from being completly parted out.

But, I have seen several '83 W123's and W126's with working tachs and ALL of them had something wadded up under their amp cover to insure a good contact...something like a folded up match book cover top. (when you do this, write something on it for future generations )

On all the 83's I've seen with working tachs, the amp is in a two inch round connector on top of the left front wheel well.
But I fear that the problem is around the inst cluster, since that was the last place of human activity....in my decades of fixing stuff, the first place to look for the problem is wherever a human interacted with it.
Richard

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'83 300 TD..."Helga" Norse for holy... a liittle rust problem
'85 300 TD...A $200 rear-ended total..being transformed into a pick-up truck
'68 Ford Ranchero GT...a pick-up truck that Ford transformed from their wagon

Since the tach worked before you pulled the cluster it's unlikely the tach module (on the L fenderwell) suddenly went bad. There is a two (or is it 3?) pin cable that plugs onto the tach, it needs to be connected and that is probably all you need to put back but the clock/tach portion of the instrument cluster also needs 12V if somehow that isn't geting there. Just put things back as they were and you should be in business!

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

It is put back like it was....I get anal and note or number all connections on a project like this...even tried reversing/flipping the tach connection. There is really only one way for the connection to go back onto the cluster, every connection is different and so it's kinda hard to screw that up even without notes!

Question...is the tach operation related to the cruise system?

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day

NO.
The cruise is driven off the speedometer flywheel (for lack of better term).
The tach is driven off the crank pulley by way of the tach module on the fender which converts the tiny magnetic pulses every time the pulley makes one revolution to a larger electrical pulse that the tach instrument can integrate into an analog.
Still Confused?

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!