Inaccurate temperature gauge reading

Sounds like a bad sending unit for the gauge or maybe a loose connection or melted wire corrosion on sending unit bad ground? Those are just some thoughts. Do you have anything that you can use to check the actual temp of the engine to verify which is incorrect ? Like a temp probe for a multi meter or a temp gun? Maybe even a cooking thermometer ? But I would start by verifying the temp then going from there.

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