Coolant Temp Question.

[Big Time]

I havent had to ask any questions since following this forum in 2 years because of the wealth of info, but I cant seem to find the answer to my particular question, some background... I converted my idiot light dash to gauges . all lights work, all gauges work even ammeter except my water temp .I have replaced my sending unit 3 times , it will work for a few days then quit registering , I have tried all the trouble shooting, ground it out , and it pegs to right. take it loose it and it stays to left . put in new unit works for a few days , then quits . added extra grounds to back of dash ,put in new gauge ,checked ohms at sending unit verified continuity at grounds etc, etc, anyone had this same issue, tired of changing sending unit. I have searched archives and seen multiple posts , I do try and research before asking questions that seem tiresome. Thanks for any input.