General Fiat Ducato 2.8D Motorhome 2003

[Darm]

HI, Just joined so if I make some mistakes please bear with me, thanks. I have a Avondale Seascape motorhome on a Fiat Ducato 2.8D non turbo and having problems starting. I have replaced the heater plugs but think I need to now test the preheat box but I cannot find this in the engine. Can anyone help PLEASE. Is it behind the air filter on the right hand side of the engine.
Any help greatly appreciated, Thanks again.

 

[goggs]

Many miles has your engine done and are heater plugs getting voltage.

 

[Darm]

Many miles has your engine done and are heater plugs getting voltage.

Hi, thanks for reply. Vehicle has done 34,500 miles but I have sorted the problem by putting in a switch, Thansk