I just removed the instrument cluster on my 83 diesel to fix the speedometer. After putting all back together and driving the car I noticed the fuel gauge and the coolant gauge flutters up and down etc. It doesn't do it so much at a stand still, but powering up and rolling it does this number. Has anyone ran into this issue. Any possible help would be appreciated.

Hi Rebe , sounds like a ground or connection issue. I'd slip the cluster back out and check the ground that's on the bulkhead just below the cluster. It could have been disturbed when you re & re'd it. The large connector at the back of the cluster may not be plugged all the way in also or there's corrosion on the connector/cluster. Good luck

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

I didn't notice any ground wire hooked to the instrument cluster removing it. The only place I thought it might be was inside of the big electrical connector to the cluster where the fuel gauge & the coolant gauges are. I thought it to be unusual that there wasn't a separate ground wire to the back of the cluster.

Yep, it seems like 90% of electric problems are caused by bad ground. Dunno the '83 but earlier versions have brown grounding wire to one of the 7mm attachment nuts.

Aint no crime in adding a ground wire to sheetmetal behind the dash, if you dont see one there already.

Otherwise, my guess is the multi prong socket isnt tight or got jarred loose reinstalling the cluster.

Sorry Rebe, I meant that there is a ground connection point in the area below the cluster. Access it when the cluster is out , unbolt it (I think there's 4 or 5 wires all attached there) clean any corrosion off with sandpaper or WHY and tighten it back up.The cluster ground runs through the connector and it's brown like 240dieseldog said.

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

Two of the screws on a w126 (if that is what you have) are ground points for the gauges.
They send the ground to the center connector (rectangle one) and then, through the speedo, it branchs out via some metal strips which are part of the whole speedo unit. Check these points where they contact the other two circuit boards (left and right).

Edit: Just noticed you have a w124 body? I think its very similar on that one too...worth checking atleast as you disturbed/changed the unit which could be causing these problems