Where does you 3 way fridge take it's power from on 12V when driving?

[Reallyretired]

In our hymer the 12v comes from the starter battery when the engine is running. It will turn to gas when the engine off unless the the fridge is set to 12v rather than auto in which case it runs off leisure. It also runs off leisure battery if s+ signal from solar controller. It's a bit of a myth that they won't cool adequately on 12v as they do. In fact in one of my past vans, on long drives I had to turn the fridge off occasionally to avoid the contents freezing as there is no thermostat on the 12v operation.

 

[Lenny HB]

In our hymer the 12v comes from the starter battery when the engine is running. It will turn to gas when the engine off unless the the fridge is set to 12v rather than auto in which case it runs off leisure. It also runs off leisure battery if s+ signal from solar controller. It's a bit of a myth that they won't cool adequately on 12v as they do. In fact in one of my past vans, on long drives I had to turn the fridge off occasionally to avoid the contents freezing as there is no thermostat on the 12v operation.

How well they work on 12v is down to the individual fridge, also the days of no thermostat on the 12v is long gone.

My last couple of vans had Dometic 8505 fridge freezers they had a 190 watt element on 12v but 250 watt on 230v, the performance was slightly better on 230v.

My current van has a Dometic 10.4 both 12v & 230v elements are 170 watt.

 

[Bill-H]

So after a lot of discussion re my melting fuse problem here - https://www.motorhomefun.co.uk/foru...engine-not-charging-leisure-batteries.290430/ I have fitted a new fuse and fuse holder (Seems to be behaving but a longer trip will be needed to check)

I did a little testing this morning and I am convinced that the fridge takes it's 12V power from the the leisure battery when the engine is running.

I am confused as I was led to believe that all motorhomes took the 12v from the starter battery/Alternator when the engine was running. My manual states there is a 20amp fridge fuse on the starter battery - which there is - but it doesn't seem to do anything. There is another 20 amps fuse (the one that melted) by the leisure and this seems to be doing the work. This fuse is not mentioned in the Burstner manual for my model.

I can see that when I turn the fridge on while the engine is running that the leisure voltage drops form 14.8 (charging voltage) to 14.3 so it clearly is drawing power from the leisure. Of course, the leisure is in turn being charged from the alternator (is that correct? or is it charged from the electroblock?) so I assume it's not a problem but it's not the way I understood it is generally done.

I have asked Burstner about this fuse but they are not willing (able?) to tell me.

BTW - it was like this from brand new - no modifications.

So, anyone know that this is the set up on theirs?

What happens if you pull that fuse out?

 

[Ditcha]

Was that the FA2 FA3 spades?

I was unsure where the power for the fridge came from because the original SCR in the ds470 was closed once the engine was started and the batteries were paralleled, but presumably once the link is connected you can manually select on the fridge? So I guess the original feed is from the alternator via B1?

 

[AdrianChen]

Many thanks!

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[AdrianChen]

How well they work on 12v is down to the individual fridge, also the days of no thermostat on the 12v is long gone.

My last couple of vans had Dometic 8505 fridge freezers they had a 190 watt element on 12v but 250 watt on 230v, the performance was slightly better on 230v.

My current van has a Dometic 10.4 both 12v & 230v elements are 170 watt.

Interesting - Ours is a 10.5 153l from 2022 (Now discontinued)- The spec for the 240v is 250w input - and for the 12v it is 170w. So I guess using 240v for me would give better results, but loose a bit through the inverter.

Still would like to change to a condenser though.....

 

[Lenny HB]

Interesting - Ours is a 10.5 153l from 2022 (Now discontinued)- The spec for the 240v is 250w input - and for the 12v it is 170w. So I guess using 240v for me would give better results, but loose a bit through the inverter.

Still would like to change to a condenser though.....

Ours is only 133Lt one of the slim ones.