Temp gauge keeps dropping and then returns to middle

[peterslimmons]

As above the temperature gauge once the engine is warm will from Time to time just drop to 60 the after a little while will return to centre. 
it’s had a major service this week at Halfords nothing was found. 
anyone k ow what this could be. 
c-max 1.5 deisel 12 plate. 
please help  

[agraham]

Thermostat sticking open occasionally and causing over-cooling?

[EmdoPL]

I have a similar issue in my MK1, the temp gauge goes up to about 87*C, then drops to about 70, and then rises up again. This goes round and round. I noticed that the radiator fan keeps turning on when the temp reaches 70*C, but the hoses are a little warm, then when the thermostat opens, the hoses get hot and then a little warm again. Changed the thermostat assembly with the sensor included, not much improvement, but still. I guess this is some wiring problem or something wrong with the PCM, so no good news for You.