Need help with Thetford N5145 DC wiring in Swift Kontiki

[Stantheswift]

We have a 2002 swift kontiki. We recently removed the old 3 way fridge and replaced it with the recommended thetford replacement the N4154. Hubby has connected 240v and gas and DC all working except for on DC when we start the engine the display goes blank. Is this because all the 12v low voltage wires we can find are only powered when the engine is off ? Do we need a permanent live to power the control unit ? There are two thick wires from the vehicle battery with the 20amp fuse into a relay which only become live when the engine is running and these are the ones we have connected for the fridge element. Does the display need to work for the fridge to keep cool whilst travelling ? I hope this makes sense because it’s really driving us mad and we are due to go away next week. Thanks in advance.

 

[Stantheswift]

That’s supposed to be a thetford N4145 sorry for the confusion.

 

[StillGoing]

The DC high current supply powers the heating element and should be live when the engine is running.

The DC low current supply powers the electronics and needs to be on all the time.

I assume you’ve also connected D+?

 

[Stantheswift]

The DC high current supply is live when the engine is running but the DC low current is only live when the engine is not running. We don’t have a D+ cable as there is a delay under the bonnet preventing power when the engine is off so we have been told to bridge this with the low current live. So do we need to run a cable directly from the leisure batter that is live all the time to the low current DC ? Thanks for your help

 

[Swifter]

Richard n Ann . Can you help with this one Richard ?

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[StillGoing]

Didn’t the old fridge have a permanent low current DC supply?

If not then you could run a new one from the leisure battery (a 2A fuse at the battery end).

 

[Stantheswift]

Unfortunately not. We thought it had but when we start the engine there is no power to those wires. All the wires we can find turn off when the engine is started except the 2 from the battery which turn on. Ok thanks this is what we were thinking we would have to do. Do we need to step the voltage down to 5v or is it ok at 12v ? I note it says low current but all wires are showing 12v on the meter. Thick and thin. Thank you for your help.

 

[Richard n Ann]

I'd run a new fused cable in from the fuse box. Or maybe you can find the low current cable in the fuse box and connect it to a permanent battery positive 12v

 

[Richard n Ann]

I note it says low current but all wires are showing 12v on the meter.

Voltage and current are different things. Everything is 12v on the van (apart from hook up)

 

[denisejoe]

Isn’t the d+ just a signal wire to turn gas off when engine is stopped

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[Stantheswift]

I'd run a new fused cable in from the fuse box. Or maybe you can find the low current cable in the fuse box and connect it to a permanent battery positive 12v

Thank you for your reply. That sounds complicated. I believe the fuse box is under the bonnet. How do I know if it’s low current ? Can I simply run a fused cable directly from the leisure batter to it ?

 

[Lenny HB]

Isn’t the d+ just a signal wire to turn gas off when engine is stopped

No, it turns the relay on that supplies the high current feed when the engine is running, so the fridge can run from the starter battery.

 

[Richard n Ann]

Thank you for your reply. That sounds complicated. I believe the fuse box is under the bonnet. How do I know if it’s low current ? Can I simply run a fused cable directly from the leisure batter to it ?

I meant the van habitation fuse box. My original fridge cable goes there and is on a 5 amp fuse.

If it's low current it will be on a small rated fuse like 5 amp and it will be a skinny wire. High current are on 20+ amp fuses and thick wire... They are all 12volts