Hi am i correct in thinking that the head unit is the unit that actually sends out the red light of the most circuit

Yes, the head unit is the master

So i have no red light does this mean i have a head unit problem

Have you been having other problems? Any DTC faults logged?
If there is no light output from the IHU then yeah, it’s not looking good for it. Try the usual suspects first, hard reset, MOST diagnostic screen

More info about the system http://media.disco3.co.uk/gallery/albums/u...ration.pdf
It’s a little generic, covering FFRR along with LR3 but the principles in this info are the same for RRS

No other issues just swapped the wires on my D4 screen yesterday as had poor radio reception then noticed i had no red light now nothing no radio no sat nav nothing but everything else is ok

Would anyone know how to test the system when i dont have power to the head unit so cant turn it on to test the most ring

Does anyone know if there is a fuse inside the head unit as i have 12 volts going in but nothing works on the head unit or somewhere i can get it tested having read the pdf Godivanige

I know my local indy has the equipment to test and repair problems with the MOST loop, but they're nowhere near you. Venture 4x4 in Warwickshire. They've sorted out a few RRS's and Discos in the past according to their FB page.

As for fuses within the head unit, no idea. I had loads of problems with mine doing very strange things, ended up buying a replacement head unit via eBay. Was very lucky in that I got a factory refurbished part that had never been fitted for £370 when they should be nearer £900. Came with a new fascia and new knobs, looked brand new and worked like a charm.

thanks have seen a few on the bay dont know weather to buy a cheapy to make sure it is that or to try and find someone who knows something about them and get it tested to confirm as i have power to the unit but nothing at all lights up or works and no light coming out of head unit

this is from the FFRR's wiki page and might [or not] help you,

http://www.fullfatrr.com/gallery/albums/us...ration.pdf

If you have 12v at the connector, and press the volume button knob the display should come on.

IIRC

no music, but display should be on.

black ground wire could be at fault

Thanks everyone just checked continuity of fuses and 43 was knackered so result cheap fix