How to connect 12V supply to new Thetford N4145 E+ (1 Viewer)

[Baggy]

I have recently had to bite the bullet and buy a new Thetford Fridge Freezer to replace my old clapped out Electrolux/Dometic. My old unit 12v was connected to a plate marked with three terminals which were marked + D+ -
A red cable was connected to the positive, a blue cable to the D+ and a Black to the Neutral. On the Fridge side of the connector the Red was matched to a Red, the Blue to a White and a Black to a Black. With the new Thetford I am faced with the problem of connecting my old Red, Blue and Black wires to a block which has a Red, White and much skinnier Purple, Orange and Black. If I were to wire these into a new strip connector, how should the old wires connect to the new. I would be grateful for any pearls of wisdom. I have connected the 240v and gas easily. The attached image shows the new prewired White plug and my old wires are lying at the bottom of the phot.

 

[StillGoing]

Page 11 of the installation manual explains it.

 

[rod_vw]

If you haven't got the instruction manual it's on here as above page 11.

 

[Baggy]

Page 11 of the installation manual explains it.

I guess it does if you understand autoelectrics. I was hoping that a kindly soul might say you connect your old Red cable to the blah, blah blah and your old Blue to the following xxxx Maybe someone else can enlighten me.

 

[Baggy]

If you haven't got the instruction manual it's on here as above page 11.

Thanks for taking the trouble to reply. Your CV is impressive m and you must know your stuff. On the other hand, I am a complete auto electrics numpty. I have 3 old wires which are Red, blue and black and I explained how they were connected to the old fridge. The new fridge offers me a Red, White,Purple, Orange and Black. Simply put, can you advise how my old Red, blue and black should match up to my new Red, white, Purple, Orange and Black.

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[rod_vw]

Thanks for taking the trouble to reply. Your CV is impressive m and you must know your stuff. On the other hand, I am a complete auto electrics numpty. I have 3 old wires which are Red, blue and black and I explained how they were connected to the old fridge. The new fridge offers me a Red, White,Purple, Orange and Black. Simply put, can you advise how my old Red, blue and black should match up to my new Red, white, Purple, Orange and Black.

As I have never seen the fridge(s) that you have I can only use what basic knowledge I have and the words in the manual.

I would assume that...

The Red wire that went to + (12v +ve) on the old fridge goes to the Red wire on the new one.

The Black wire that went to - (12v -ve) on the old fridge goes to the White wire on the new one.

The Blue wire that went to D+ (engine charging signal) on the old fridge goes to the Orange wire on the new one.

However from your description of the connections to the old fridge there was either no electronics in it or they were powered from the +ve & -ve wires internally.
Your new fridge seems to need an independently fused low current supply via the Purple +ve and Black -ve. I'm assuming that you have no convenient way to obtain a second feed separately from your leisure distribution box so you could connect the Purple +ve via a 1A fuse (I doubt you will ever find such a thing as a 1.1A fuse as per the diagram) to the Red wire that went to the +ve as above and connect the Black directly to the old Black wire.
If you are able to extend the wires to and from the fuse to place the it in an accessible location then all the better just in case it should blow in the future. Sods law says if you make it accessible it will never blow but if you don't you will need to get to it!

PS -- there is no such thing as Neutral in vehicle direct current (DC) wiring it's usually considered as the -ve or chassis ground wire.

I hope that someone who has seen your fridge will come along and confirm or deny my ramblings.

 

[Baggy]

As I have never seen the fridge(s) that you have I can only use what basic knowledge I have and the words in the manual.

I would assume that...

The Red wire that went to + (12v +ve) on the old fridge goes to the Red wire on the new one.

The Black wire that went to - (12v -ve) on the old fridge goes to the White wire on the new one.

The Blue wire that went to D+ (engine charging signal) on the old fridge goes to the Orange wire on the new one.

However from your description of the connections to the old fridge there was either no electronics in it or they were powered from the +ve & -ve wires internally.
Your new fridge seems to need an independently fused low current supply via the Purple +ve and Black -ve. I'm assuming that you have no convenient way to obtain a second feed separately from your leisure distribution box so you could connect the Purple +ve via a 1A fuse (I doubt you will ever find such a thing as a 1.1A fuse as per the diagram) to the Red wire that went to the +ve as above and connect the Black directly to the old Black wire.
If you are able to extend the wires to and from the fuse to place the it in an accessible location then all the better just in case it should blow in the future. Sods law says if you make it accessible it will never blow but if you don't you will need to get to it!

PS -- there is no such thing as Neutral in vehicle direct current (DC) wiring it's usually considered as the -ve or chassis ground wire.

I hope that someone who has seen your fridge will come along and confirm or deny my ramblings.

As I have never seen the fridge(s) that you have I can only use what basic knowledge I have and the words in the manual.

I would assume that...

The Red wire that went to + (12v +ve) on the old fridge goes to the Red wire on the new one.

The Black wire that went to - (12v -ve) on the old fridge goes to the White wire on the new one.

The Blue wire that went to D+ (engine charging signal) on the old fridge goes to the Orange wire on the new one.

However from your description of the connections to the old fridge there was either no electronics in it or they were powered from the +ve & -ve wires internally.
Your new fridge seems to need an independently fused low current supply via the Purple +ve and Black -ve. I'm assuming that you have no convenient way to obtain a second feed separately from your leisure distribution box so you could connect the Purple +ve via a 1A fuse (I doubt you will ever find such a thing as a 1.1A fuse as per the diagram) to the Red wire that went to the +ve as above and connect the Black directly to the old Black wire.
If you are able to extend the wires to and from the fuse to place the it in an accessible location then all the better just in case it should blow in the future. Sods law says if you make it accessible it will never blow but if you don't you will need to get to it!

PS -- there is no such thing as Neutral in vehicle direct current (DC) wiring it's usually considered as the -ve or chassis ground wire.

I hope that someone who has seen your fridge will come along and confirm or deny my ramblings.

You are a gentleman and scholar Sir and your ramblings are very welcome. I will revisit the Van and the problem in the next few days. Many thanks.

 

[autorouter]

I think rod_vw's description will get the fridge working , but here's a bit more info you may find useful.

The old fridge had a 12V element that was powered from the alternator/starter battery while the engine was running, and switched off when the engine stopped. So there was a red positive and black negative to power the fridge heater element, and a D+ signal to turn it on and off when the engine was running or stopped.

The new fridge is more complex, and has an electronic control board which can automatically switch the three heat sources (240V, gas and 12V). It needs a permanent 12V supply, ie one that doesn't go on and off when the engine starts and stops. It is usually called the Low Current (LC) supply. That will be the two extra thin wires, purple positive and black negative. Usually that supply is taken from the leisure battery.

I don't know how easy it would be to run a couple of thin wires from the leisure battery, probably from the 12V fusebox. It's a small current, so you might be able to tap into the supply for the heater/water heater if it's nearer.

The old fridge wires can be used as the High Current (HC) supply, since they will supply power to the 12V fridge heater element just like the one in the old fridge. They are thick wires, red positive and white negative. They can connect to the old red positive and black negative power wires.

The D+ connection is simple, the new orange D+ connects to the old blue D+ cable.

The new fridge uses the D+ in several ways. As before, it turns on the 12V element when the engine starts, and turns it off when the engine stops. It also automatically turns off the 240V/gas when the engine starts. It automatically turns on 240V if hookup is available. If no hookup, it turns on the gas automatically.

When the engine stops, there is a 15 minute safety delay before the gas turns on automatically. This is to avoid firing up the gas flame if you stop for fuel at a gas station. If your fuel stop is longer than 15 minutes, ensure you manually turn off the gas to avoid an accidental fire hazard.

 

[rod_vw]

I think rod_vw's description will get the fridge working , but here's a bit more info you may find useful.

The old fridge had a 12V element that was powered from the alternator/starter battery while the engine was running, and switched off when the engine stopped. So there was a red positive and black negative to power the fridge heater element, and a D+ signal to turn it on and off when the engine was running or stopped.

The new fridge is more complex, and has an electronic control board which can automatically switch the three heat sources (240V, gas and 12V). It needs a permanent 12V supply, ie one that doesn't go on and off when the engine starts and stops. It is usually called the Low Current (LC) supply. That will be the two extra thin wires, purple positive and black negative. Usually that supply is taken from the leisure battery.

I don't know how easy it would be to run a couple of thin wires from the leisure battery, probably from the 12V fusebox. It's a small current, so you might be able to tap into the supply for the heater/water heater if it's nearer.

The old fridge wires can be used as the High Current (HC) supply, since they will supply power to the 12V fridge heater element just like the one in the old fridge. They are thick wires, red positive and white negative. They can connect to the old red positive and black negative power wires.

The D+ connection is simple, the new orange D+ connects to the old blue D+ cable.

The new fridge uses the D+ in several ways. As before, it turns on the 12V element when the engine starts, and turns it off when the engine stops. It also automatically turns off the 240V/gas when the engine starts. It automatically turns on 240V if hookup is available. If no hookup, it turns on the gas automatically.

When the engine stops, there is a 15 minute safety delay before the gas turns on automatically. This is to avoid firing up the gas flame if you stop for fuel at a gas station. If your fuel stop is longer than 15 minutes, ensure you manually turn off the gas to avoid an accidental fire hazard.

I guessed that what you have said autorouter was what the OP had fitted but never having seen it I was working from basic principals. There is no problem in 'piggy backing' the low current supply onto the main, it just means that there is only one (the main one) fuse supplying the whole thing so if that blows for some reason the complete fridges and its additional supplies don't function.

 

[IRHP]

Hc= high current from a charging leisure battery or engine battery when engine running. Doesn't matter which as they are both linked.
Lc= low current permanent 12v for fridge controls
D=d+ from alternator

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[rod_vw]

Hc= high current from a charging leisure battery or engine battery when engine running. Doesn't matter which as they are both linked.
Lc= low current permanent 12v for fridge controls
D=d+ from alternator



View attachment 906544

Unfortunately many modern vehicles have 'smart alternators' which usually don't have a d+ wire. The correct way to provide this signal with vehicles of the VAG marque is to use a special signal from the Body Control Module to switch in additional loads but these need the wire connecting to the BCM and having it coded. The advantage of this is that the BCM can 'Load shed'. I can but assume many other marques have a similar facility.
The simple method, but perhaps not ethically correct in the vehicle manufacturer's eyes, is to use an ignition switched live to do the job either direct (via a fuse) or via a relay and appropriate fusing.