Worcester 37CDi pump running?

The pump seems to be running for longer than normal periods when on auto and the temp settings are lower than room temp. Despite the anti sieze feature the pump should only run for a short time, also the boiler temp guage shows 59 and none of the rads are warm. I recently changed a rad and refilled the system and used Fernox F1 but that should not have affected the boiler. Any ideas?