[rwg200]

It appears to be the ECU controller but not much to go on from this picture.  In your post, you say it won't start and later say it will run if the solenoid is tied back.  How do you get it started?

I'll be glad to help you work through this problem and maybe you can benefit from the experience.  You'll need some testing equipment, mainly a volt/ohm meter and possibly a test light.

My first thought, since when it is running tied back, there is no hold voltage to the solenoid.  Let me explain the solenoid on your set.  It has three wires, a common (black and connected to battery negative or sometimes called ground), a white which is pull in, and a red which is hold in.  The pull in does just what it is called, pulls the slug of metal back or inside the solenoid,  then the hold in keeps it there.  The current draw for pull in is high whereas the hold in draws very little.

The first test is to put a test light (or voltmeter) on the red and ground with the solenoid tied back temporarily.  If there is voltage, there is a problem with the solenoid.  If no voltage, the controller is not making the IGN circuit go high.  The IGN circuit powers all devices such as the alternator, the hold in, auxiliary items such as cooling fans, and any other items that need to operate to keep the engine running.  As someone mentioned previously, the fire extinguisher has a pressure switch contact in series with the hold in.  If it is open, no hold in.  Newell has used a square four pin trailer style connector in the past to connect the pressure sw into the hold in circuit.  You can unplug and test for continuity on the pressure switch side of the connector, you may have to untape some of the connections of the plug to see which wires to connect to.  If it is made (or closed) the problem is somewhere else.

@yachts mentioned a low water level switch.  It is located in the surge tank (likely but could be somewhere else).  This switch connects to the controller in the fault system.  If the controller sees this switch closed, it will prevent IGN from going high (or +12).  If you disconnect one of the switch wires, the fault signal goes away.  DON'T leave it disconnected after testing as it protects the engine from proper low cooling fluids.

You also mentioned:  If i hold the switch on it flashes the green light 4 times which states that its not seeing AC, i have no idea what this means!
The controller also looks at the AC output voltage of the generator.  If the set was not running there wouldn't be any AC, if it was running,  then there is a problem in the generator.  do you have generator AC inside the coach?



I'm being wordy here since I don't know your level of expertise so, don't be offended if the explanations are too elementary.  You can PM me if you like or text.  my info is on this site.

Good luck and keep in touch.

Thanks Gordon for your detailed reply,
Im actually in New Zealand at the moment and will be back in the UK on Thursday next week when i can take more pictures.
To answer some of your questions, i have managed to get the Genny to start by running a temporary cable from the solenoid to the panel at the front of the genny, i have taken the control panel cover off so i can find a live. i cable tie the stop arm open and then just touch my temporary cable to a live to turn the genny over and it fires right up. If i don't cable tie the stop arm open it fires up but stops immediately.
I think it is more likely to be sensor related as sometimes it will fire up correctly with any of the start switches, either on the genny, above the drivers seat or from the Silver Leaf Pannel.
If it is operating correctly i will flick the start switch above the driver seat for example and the green light next to it will flash several times as the pre heat is working i guess then it fires up.
If it is not working correctly i push the start switch, the green light comes on but as soon as i let go of the switch it just doesn't flash any more suggesting it is not going through its pre start procedure.
If i hold the start switch on (either at the drivers seat or at the genny it flashes the green light on a 4 flash cycle which if i read the fault codes written on the side of the genny by the start switch says no ac, i think now this is probably a code saying its not producing AC as the genny is not running and actually not a code to do with starting,
Once the genny is running after a hot wire start it operates perfectly producing the correct power at all the outlets.
I do believe it will be a sensor issue now having read your reply and thinking about it as when it does work properly (which very rare now) it is perfect. so i don't think its  anything to do with the solenoid as this works fine when the system goes through its correct start up procedure.
I think the next move as you say is to fool the system into believing the water level sensor or fire suppression systems are working ok. I don't know that they are not but this seems the best place to start!?
I hope my ramblings make sense and have cleared up some of the confusion!!?
Once again thank you for taking the time to send such detailed reply and i will definitely be reaching out to you for advise once I'm back with the coach!
Cheers
Rob