p38 coolant change (strange)

evening all, bit of a weird one since changing the top thermostat gasket over as old one leaked a bit and changing the antifreeze my temp guage doesnt move off the cold mark. have had the cap off bleeding it up with heaters on full. think there arent any air locks. heaters work pukka as they did before.

any ideas?

Try to burp systen by squeezing hoses. When happy that there are no airlocks. Check that wire is connected to temp sender.