Why is my temp gauge doing this

[Vidma]

Its work perfect till 80+ ish c and then jumps to 120c i tried to replace the sensor itself it didn’t help

 

[gsxr]

Most likely a bad wiring harness. Has the engine harness ever been replaced? Check for insulation flaking off the wires. Also check the date code on the tag of the harness.

 

[Vidma]

this is a 1992 w140 but i replaced the harness

 

[gsxr]

Check connections on both ends... could also be a faulty gauge. Might be difficult to pinpoint / diagnose.

 

[emerydc8]

I’m dealing with this exact issue now. I’m almost positive it’s the gauge. Last winter on cold starts the temp needle would stick at off-scale low, but once I drove it a few minutes if I tapped the cluster with my knuckle it would wake up and indicate the likely temperature (e.g., 60 C). If I ignored it, it would wake up by itself as it got closer to 80 C. Fast-forward to this summer, when it gets to about 95 C in stop-and-go traffic the needle starts bouncing up to the red line and back. I am going to have to pull the cluster and replace the indicator from another cluster. Even though I know it’s not that hot because the high-speed fans work off another sensor and they would have activated (around 92 C with the Cool Harness mod), it still bothers me and I need to fix it.

 

[Vidma]

I have the exact same problem where i have to tap the cluster i replaced the sensor itself now its a bit jumpy but i also wanted to ask is it normal to get 2+v to the wire while its in ignition?