Fiat Ducato radiator fans

[Manic]

If I’m not careful my radiator saga will end in suicide.
I lost all coolant from the header tank in my 2001 Fiat 2.8idtd based Hymer.
I ordered new rad from eBay , arrived damaged-returned with eventual refund, order another from Coastal Motorhomes, fitted and then it leaked-manufacturing fault, Coastal refunded stray away, then ordered a original old stock one from eBay, fitted that leaked from end cap, radiator specialist tested found leak and swapped old end cap on to new rad, lovely rad reinstalled (3rd time-at least I’m getting quicker fitting it)
Sitting in the van 2 a day later and at 8.30pm the rad fans come on, flat out, disconnected the rad switch to stop them , cleaned plug with contact cleaner but as soon as I plug switch back in the fans start.
Any suggestions, please

 

[Figaro]

Is there a thermostat somewhere that switches it ?
Presumably it's sticking or gone faulty, no idea where it would be though

 

[chain driven]

If I’m not careful my radiator saga will end in suicide.
I lost all coolant from the header tank in my 2001 Fiat 2.8idtd based Hymer.
I ordered new rad from eBay , arrived damaged-returned with eventual refund, order another from Coastal Motorhomes, fitted and then it leaked-manufacturing fault, Coastal refunded stray away, then ordered a original old stock one from eBay, fitted that leaked from end cap, radiator specialist tested found leak and swapped old end cap on to new rad, lovely rad reinstalled (3rd time-at least I’m getting quicker fitting it)
Sitting in the van 2 a day later and at 8.30pm the rad fans come on, flat out, disconnected the rad switch to stop them , cleaned plug with contact cleaner but as soon as I plug switch back in the fans start.
Any suggestions, please

Hi you say both fans are running. That would indicate that the control box ( located on the fans housing) is faulty they are prone to water ingress due to there position .hope this helps

 

[Manic]

Is there a thermostat somewhere that switches it ?
Presumably it's sticking or gone faulty, no idea where it would be though

There’s a switch in the bottom of the rad, but I would like to check before buying a new one and draining coolant again.