Welcome to justanswer.com
Inside fusebox = Fuse#40 is for heater and Air con circuit
Underbonnet fusebox = sends power to the internal fusebox
Does the heater still run when fuse has gone ?
everything works...radio,heater,lights, car just wont start....thought maybe it had something to do with the fuel system. The only code i get is P2300 witch is a bad coil. But dealership says the car should still start and something else is blowing fuse 40.
Fuses on the SB fusebox on vehicles made from May 2005 show that SB40 in the E-box under the hood is for all four ignition coils. This is if you have an E-box HIGH, meaning you have 54 fuses in that fusebox, as opposed to E-Box LOW which has only 30 fuses (so can't possibly have a fuse 40)
The component location from before November 2004 shows fuse 40 powering fuse panel SC (inside the vehicle on the left end of the dash)
So, you're going to have to replace one or all of your coils. You could try unplugging them one at a time and see if the fuse blows, but if the car runs it will be chugging on three cylinders, so don't run it long.
Sometimes you can tell which coil is bad by the smell- they have a rancid electrical burning smell, and may be heated, broken, or melted-looking (though most of the failures in recent years haven't been so spectacular!)