TD5 Temperature problem

My temperature gauge has started to register max temp. but engine is normal temp. when this happens I switch off after 2 minuets switch back on and temp. is normal. I have changed temp reader in cylinder head and renewed drive belt, but this problem still happens. Can any one help with diagnosis please.

Derek S

19J is a four cylinder, you may get more help in the TD5 section.

hiya i had this ..its the wrong sensor will be a 200 not a 19j sensor