Your scenario is entirely possible and one I hadn't thought of although it even happened to me with a Mazda pickup after I upgraded to a two core heavy duty radiator. Went back to the single core and the cycling stopped.
My comments were based on my experience with an original equipment car and how the problem was resolved. I still have no reason to believe that the gauge in my 122 was not shot.
Does that Dodge use a mechanical or electrical gauge?
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'86 745T, '72 144E, '70 145S, '68 122S Estate, '60 544
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