Thanks for your reply,

In response to your reply, I have no leaks under the dash. The instrument
cluster was removed about 6 years ago and I've had this problem for about 2 years.I changed the thermostat,sending unit,wire and connector.The other 2 gauges within this cluster work fine,( Oil & Fuel) I haven't as of yet disconnected the wire from the sending unit to see if it jumps.I will do that this week and let you know the results. If I tap the gauge with my finger
and it returns to normal then why can't I assume that the problem is in the cluster. Maybe a faulty wire or ground in the back of this cluster.

Thanks again for your prompt reply, Richard Tripi