89 mustang 5.0 temp gauge

[mustangIIfan]

Short story is its an 1989 mustang GT convertible 5.0 auto and recently i been experiencing the temp gauge taking a while to register any reading even after the engine has warmed up (i know cause the upper rad hose is hot so i know coolant is flowing) now it has stopped working altogether i just replaced the coolant temp sensor and still nothing. My question is i am about to remove the cluster and inspect is there anything particular i should look for out of the ordinary in the cluster? Does anybody have any other ideas i could try as well? when the engine is off and key out the gauge seems to move to its normal operating range on its own but turn it to on and when its running that's when it goes back to nothing don't know if that helps out yes i already have a repair guide but have exhausted my options there Thank You