Cooling fan not working 2.0 hdi

[op2097]

Hi,

Noticed my fan on my new to me 2002 m49 2.0 hdi won't run. 

Temp gauge went to 3/4 on idle before I turned it off. 

The green relay on the fan assembly up front was a bit corroded, I opened it up and touching the switch inside with a screwdriver makes the fans run so there is power to them. 

Replaced the relay. 

No fan running when hot. 

Any ideas where to look next? 

Thanks

[Kieron G]

Not sure with 2.0 hdi but our 1.8 petrol has a sender threaded into the radiator which I think switches the fan. If the same system could you check there is a supply to it then take it out and test it in boiling water with a multimeter