Help with wiring from Domestic RM6401L to Thetford N4090E

[Delboy]

Can any help I have removed my old Dometic 3 way fridge and replacing with a Thetford 3 way, the wiring is not the same, I have worked out the AC but DC I have 4 wires 2 being the live and neutral from the leisure battery and the thicker 2 from engine battery I believe, the new fridge has a plug with 5 wires, do I need to link any of the wires, there is also a CI-bus cable at the back with a plug where dose this plug into ?

 

[r4dent]

The wires from the Leisure battery power the internal light and the control board.
The thicker wire (should be from the alternator rather than the engine battery) power the fridge in 12v mode when the engine is running.

Do you have a manual for the Thetford? This should have a wiring diagram

 

[Delboy]

Thanks for the reply, I do have a manual, I will try and attach, do I take the alternator live wire to orange (D) and with the 12v live do I link between LC and HC ? Thanks in advance for your advice.

 

[merl]

Hi, Having looked at the Thetford fitting instructions here https://www.thetford.com/app/uploads/IM-N4000.pdf The information on page 9 shows a power connector like this,

assuming you're fridge has this connector then:-
The thick positive cable from the starter battery goes to Red 5
The thick negative cable from the starter battery goes to the white 1
The thin positive from the leisure battery goes to the purple 3
The thin negative from the leisure battery goes to the black 2

There is also an orange wire (4)which is supposed to go to the ignition D+, This D+ connection is energised with 12V ONLY when the engine is running so that the fridge only draws 12V power from the starter battery when the engine is running. This D+ connection wasn't used by your old fridge and so almost certainly isn't available at the rear of the fridge, this is because the D+ switching was being performed by an external relay probably in your vans PDU and as such only provided 12v to the fridge cooling side (via the thick cables) when the engine was running. So when you said that the the thick positive went to the starter battery I'm assuming you mean it goes to the starter battery via a relay and is only 'live' when the engine is running? IF that's the case then linking the orange wire into the red/thick starter + cable junction should do the trick and fool the inbuilt circuitry, ideally stick a 3A fuse in the orange feed.

The CI bus is an industry standard for of communication interface that lets you see details of the fridge on a common central control panel. it;s relatively modern and not available on older vans and in that case just leave it unconnected.