Cooling fans odd behaviour

[stain]

Recently my fan has started playing up. It now comes on at about 50deg instead of 90deg and doesn't stop running until engine switched off. I have an override switch fitted (to turn it on) and pressing that makes no difference. What's going on?

[rigga]

Otter switch (Rad fan switch) is playing up.

[stain]

Thanks. Last time it failed the fans didn't come on at all.

[rigga]

Its happened both ways to me, no fans, and fans constantly on.