Hi all , I've had a temp sensor fitted to cylinder 3 on my classic but all its showing is 50 constantly and not changing the gauge is working as I see it count up when turned on any ideas what can cause this would a bad earth from the adapter plug to the engine block do this as I did notice a small blob of what looks like silicon next to it ? I'm using a 2 wire temp sender

 

Try earthing the outside of the gauge to the block with a short bit of wire bared at both ends. have someone watch and see if the gauge moves.

If not:

Check that the wires/plugs are secure at the sender, any joints along the way and at the gauge.

Check that the wires are connected the right way round.

Finally, suspect the sender might be faulty.