1998 Ductato - why 2 fans?

Hi, I run a 1998 2.8 no turbo LWB. The engine has been running a bit hot for some time and today I replaced the radiator.

I'm confused about this vehicle having twin fans. The smaller one of the two kicks in and out when the gauge needle is vertical. The bigger fan doesn't seem to run at all.

How should the bigger fan work - same time as the smaller one? at a different temp?

Overall the engine seems to run hotter than it did up to 2 years ago (had the van 8 years) and I've got a feeling, the bigger fan not working is the reason.

any pointers at all on why 2 fans and when should they both work?

Thanks

Hi,
I could be wrong, but I understood that the fans on some models worked at different temperatures.
And they fail as well.
It's very common for the older vans to start to run warmer, usually a new radiator and a good flush sorts it out, but it's worth replacing the switch for the fans at the same time.
Mine (1.9td motorhome) has started running hotter in recent years, usually when I put my foot down, I have wired a switch on the dash to turn on both fans by hand, until I replace the rad.
Google "Ducato overheating" and similar, there's all sorts of responses and tips.

mines definately running hotter than it did for the first few years. I thought this was down to the rad getting on a bit. Now the rads been replaced, it runs slightly cooler but still hotter than earlier and the fan cuts in much earlier. does the main fan that isnt working on mine have a seperate relay or fuse does anyone know?