Relays under drivers seat

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Da dan
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Relays under drivers seat

Post by Da dan »

I have a 85 Devon and under the drivers seat by the start battery are two relays/inline fuses. I’m guessing one is split charger and one for the fridge? But why to the starter? Not radio as that is off the leisure battery. I have bought a smart charger so want to take them out if pos? Thanks in advance


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1664
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Re: Relays under drivers seat

Post by 1664 »

Both the split charger and fridge relays will trigger once the engine is running, the split charger effectively connects the starter and leisure batteries together to allow the alternator (which is connected directly to the starter) to charge them both and the fridge relay connects the fridge 12v element to the alternator too so it doesnt really matter.
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Da dan
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Re: Relays under drivers seat

Post by Da dan »

On a bit of what looks like 1.5mm cable?

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Da dan
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Re: Relays under drivers seat

Post by Da dan »

Is that not a fire risk with such thin cable?


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davidoft1
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Re: Relays under drivers seat

Post by davidoft1 »

Da dan wrote: 22 Mar 2021, 19:20 Is that not a fire risk with such thin cable?


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No, it’s fused accordingly

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Re: Relays under drivers seat

Post by Mocki »

If that’s either the split charge or the fridge it’s pointless .....

a three way fridge needs 11amps @14v on 12v setting to be effective....  if that’s the fridge, it’ll be fuelling the "it’s only good for maintaining the temperature " brigade .....
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Da dan
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Re: Relays under drivers seat

Post by Da dan »

Fair enough. How would I go about testing? I’ve taken out the fuses to see as I’m getting a flat start battery due to knackered Leisure battery. My thinking this is the only thing that connects them? Unwired the fridge on the switch years ago after one of the kids was playing with it and left it on. Thinking of changing fridge too Waeco Crx50 as seems to only draw 1.7amps so with a new 150 amp battery and solar should be sorted for a good weekend?


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Re: Relays under drivers seat

Post by 1664 »

Those should be the only things connecting the starter and leisure batteries together and then only with the ignition on. It should be impossible to run the fridge on 12v without the engine running/ignition on so your kid playing with it shouldn't affect anything unless he physically changed the connections. Disconnect the leisure battery and see if the starter battery still goes flat, it has to run the clock and radio memory constantly and if it's shagged then that will  be enough to flatten it if the van isn't being used.

The fridge is only meant to be used on 12v when you are driving along not when you are parked up. When parked up you use it on gas unless you are on hook up in which case you power it off the mains. It seems a lot of people take out perfectly good three way fridges and fork out to replace them with compressor fridges. A fridge running on gas uses a lot less electricity than a compressor fridge no matter how good they are (and its silent).
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keynsham1
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Re: Relays under drivers seat

Post by keynsham1 »

I have read this post with interest as I am rewiring my van completely. As was said to me when I bought it, The wiring is usually done by a carpenter, and I think mine was!!

My Fridge 12V supply is wired to the leisure battery for 12V, not the alternator, but only connects when the engine is running and the relay is activated. Is that common? Everywhere I look, I read that the 12V for the fridge should come from the alternator, but usually it has been written for a caravan not a camper van.

I also have a second relay that seems to do nothing as it connects the leisure battery +ve back to itself!!

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Re: Relays under drivers seat

Post by Mocki »

The biggest problem with three way fridges is most wiring info for them is for a caravan . This is also where the myth that the 12v elements are only for maintaining the temperature, and they will not cool ....it’s rubbish ! 
most three way fridges have roughly the same power heating element on 12v as they do on mains , so if the wiring is up to the job they will work just as well on 12v . 
If the supply cable is thick enough to take the current needed without causing voltage drop , they will work very well . 
The whole taking power form the leisure battery thing is a throw back to caravanist , who can only supply a poor amperage to charge from from the tow vehicle . We don’t suffer those issues, we can run meaty cable that can supply the amps from the main battery direct to the fridge heating element via a alternator switched relay .
You will need at least a 30amp auto relay for the fridge ( fridges need a bit less than half this , but you should never run anything at its limit if you want it to be reliable ) and exactly the same circuit for the split charge , except it needs to be able to supply at least the amperage rating of your alternator , because potentially if the leisure battery was flat it could try and take maximum amperage . I would go for a 100amp relay and cables capable of 50amps .
personally I wouldn’t entertain a Voltage Sensing Relay , they are more hassle than worth , and frankly running one trigger wire from the alternator is much easier and reliable .

 
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Da dan
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Re: Relays under drivers seat

Post by Da dan »

So if I reconnected the fridge and turn it on via the switch do I also switch the zig unit on to power the fridge then turn off when I stop? Or leave the unit off? I only ever use it on gas but would be nice for the longer journeys. I think some testing time. Thanks


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