Fridge on 12v (1 Viewer)

[Feltwell]

I've noticed on longer drives, in fairly hot sunny weather ( 30 degrees or so) that by the end of the day the freezer contents are still frozen, but ice cream is very soft, and the fridge contents aren't as cold as usual.

I know that 12v whilst driving isn't as effective for powering the fridge as 230v or gas is when you're parked up, but I thought the 12v setting would be enough to maintain the temperature.

What do others find? Just trying to guage if I need to start fault finding the 12v system. Fridge is on the automatic setting, and flicks over to 12 v as soon as the engine is started with no problem, according to the display at least. Similarly, when stopped, the fridge does as it's supposed to on the auto setting and switches off for 15 minutes then switches to gas.

 

[pappajohn]

Your fridge will only lower the temp by around 20°c below ambient temp so at 30°c it will attain around 10°c

On 12v it wont be this efficient which is why your icecream is now yoghurt.

 

[Techno]

My fridge works just as well on 12 volts
as mains
RMD8505

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[Neil S]

Ours works fine on 12volt even when it was 90f near Montelimar it kept everything in the freezer solid , expected it to defrost but it was fine whilst on the move

 

[pappajohn]

Ours works fine on 12volt even when it was 90f near Montelimar it kept everything in the freezer solid , expected it to defrost but it was fine whilst on the move

The op's freezer is still frozen.....its the fridge not going low enough.

Come to think of it......ice cream in the fridge !!!, no wonder its thawing.

 

[lorger]

if ours has been on gas or mains before travelling the 12v normally maintains the temp,

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[scotjimland]

First of all, lets put this myth to bed... There should be no difference in the cooling on 12vdc, 240vac or LPG .. the wattage, and therefore the cooling power of each energy supply is aprox. the same..
Depending on fridge model, typically 120watt element on 12v and 125watt element for 240v


Has it always been like this or is this a new problem. ?

If it's always been like this then first thing I would check is the 12v wiring.. depending on the cable run it should be at least 2.5mm up to a 5mt run.. , on runs over 5 mts Dometic recommend 4mm ... At 120watts it's pulling 10Amps..

Convertors don't always fit the correct size cable.. too thin a cable, and the volt drop will greatly affect the element wattage which reduces the cooling.
(NB> That is cable cross section area in sq mm .. not cable diameter.. )

If that's ok, you need to check that it has at least 12v when the engine is running.. this needs to be done at the back of the fridge on the 12v supply connections.... if below 12v then there may be a poor connection, or a problem with the split charge relay..
(be mindful there are TWO 12v supplies.. one, a permanent supply for the electronics and interior light, the either only live when engine running, the one we are checking )

If all that checks out ok.. then you need to look at how it's being used.. Overfilling will reduce the air flow around the shelves.. so products get warmer.. not unusual for people to pack it full before a journey.. There should be adequate space between the shelves and the evaporator to allow a good air circulation.

Is the door seal damaged.. have you noticed the fins on the evaporator getting iced up ? If so that also reduces the cooling .. the ice acts as an insulator.. preventing proper cooling.

If that's ok,.. when did you notice this problem .. was it climbing up and down hills.. out of level the fridge won't work properly.. but you would need to be doing that for long periods to have a detrimental effect..

Operational Specs. from Dometic..
Thermostatic control for 230-volt mains and gas operation
Refrigerator +7°C, freezer compartment up to -12°C at ambient temperatures up to 32°C

 

[Shrimp]

I've always understood the fridge works on max whilst on 12V-no thermostat.
Ours is working well now in France-day temp of 30° upwards but it still doesn't like ice creams unless they are flat on the freezer floor, ice cubes-no problem!

 

[Feltwell]

The op's freezer is still frozen.....its the fridge not going low enough.

Come to think of it......ice cream in the fridge !!!, no wonder its thawing.

Eh? No, the ice cream is in the freezer, it's the whole fridge freezer that seemed a bit warm!

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[scotjimland]

I've always understood the fridge works on max whilst on 12V-no thermostat.
Ours is working well now in France-day temp of 30° upwards but it still doesn't like ice creams unless they are flat on the freezer floor, ice cubes-no problem!

Correct.. no stat on the 12vdc energy supply

when we were in France this summer it was often 32c or more.. and had no trouble with fridge or keeping ice cream in the freezer..

 

[Feltwell]

Thank you scotjimland, very useful. I've definitely got the correct 12v supplies to the fridge, I checked those a few weeks ago when fitting fridge fans. The supply cable from the "engine" supply was fairly chunky, what exact size I'd need to check.

Has it always been like this? Well,hard to tell, to date the van has been holidaying in the UK so sustained high temperatures outside weren't really a problem!

I shall do some investigating if others find theirs are just as good on 12v. I presume the 12v heating element is a separate item to the 230v one? So it's possible that has gone.

 

[scotjimland]

I shall do some investigating if others find theirs are just as good on 12v. I presume the 12v heating element is a separate item to the 230v one? So it's possible that has gone.

Yes.. two separate elements .. but they either work or don't work..

if it has gone there would be no cooling, but it is quite possible , as you may not notice it's not working on short trips.. it may only become apparent on long journeys..

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[DBK]

This is a good fridge thermometer, they are used in some hospitals to check the temperature drugs are kept at. No doubt you can get much cheaper ones from fleabay but it is well made - ours has been seriously chewed by the dog but is still working.
http://thermometer.co.uk/catering-thermometers/418-fridge-or-freezer-alarm-thermometer.html

 

[mike mcglynn]

Hi,DBK whilst your dog was chewing the thermometer was it a hot dog

 

[JockandRita]

This is a good fridge thermometer, they are used in some hospitals to check the temperature drugs are kept at. No doubt you can get much cheaper ones from fleabay but it is well made - ours has been seriously chewed by the dog but is still working.
http://thermometer.co.uk/catering-thermometers/418-fridge-or-freezer-alarm-thermometer.html

That's the very same one we use to monitor the fridge temperature for storing Rita's meds, as the temperature has to be maintained between 3 and 10 degrees Celsius.

Our Electrolux AES Fridge/Freezer unit works a treat off the 12v supply, but we've never relied upon 12v to bring the temperature down initially, only to maintain it.

@Feltwell. Good luck sorting it out.

Cheers,

Jock.

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[2657]

We had not used our fridge for a few weeks and tried an experiment as I had read that these fridges don't work as well on 12v.

I switched the fridge on 12v, without prior cooling, at the beginning of an 8 hour journey from North of Inverness to Manchester, when we arrived the fridge had cooled to its normal operating temperature.

 

[SUGGY]

a tip from another site was to put a freezer pack in the fridge to help maintain the coldness , we put one in the freezer section as well once we have made a bit of space ,
we also run the fridge off the inverter , via solar and batteries , thus saving gas ,

 

[scotjimland]

a tip from another site was to put a freezer pack in the fridge to help maintain the coldness , we put one in the freezer section as well once we have made a bit of space

how does that work.. are they pre frozen before leaving home.. ? If so they will soon be at the fridge temperature, so a short term cooling effect and eventually just another product in the fridge.. using up valuable space..

we also run the fridge off the inverter , via solar and batteries , thus saving gas ,

yes, you can run off your inverter to save gas.. only uses about 0.5A on 240v

but you will need 10Amps from solar to do that without running the battery down.. , 125w / 12 = 10.4A

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[SUGGY]

Yes .
260 w solar panels and 2 x125 amp batteries .
Put fridge on inverter around 10 am then back on gas at around number 1 at 4 / 5 pm for the rest of the night .

 

[Feltwell]

Definitely something up with my fridge. On auto as usual, appeared to switch to 12v as usual when we started off today, but after a stop the fridge started buzzing an alarm as soon as the engine was started.

So, for now, just running on gas - manual confirms I can drive with it on gas. Another thing to fix when I get home!

And before anyone asks, yes I have got the regulator type that you can use safely whilst driving.

 

[Techno]

It sounds like the relay controlling the 12 volt with engine running is either stuck open or lost the D+ feed from the alternator (fuse blown)

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[Sidney]

I run mine on gas when travelling. 12v just doesn't maintain the temperature.

 

[scotjimland]

12v just doesn't maintain the temperature.

something is amiss.. it should no problem.

 

[peterc10]

something is amiss.. it should no problem.

I agree. We run our fridge and freezer on 12V when travelling and everything remains cold or frozen all day.

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[Techno]

If it didn't then it might as well be a two way fridge

 

[Robert Clark]

Motorhome fridges are crap!
And struggle when it's over 25 deg outside.

Fitting external fans to the top vent helps.

But fitting an internal fan really helps keep the fridge temperature more even

I fitted one myself
http://www.motorhomefun.co.uk/forum/posts/1945106/

 

[Feltwell]

It sounds like the relay controlling the 12 volt with engine running is either stuck open or lost the D+ feed from the alternator (fuse blown)

I think you're on the right track Andy. Back home today, time for a quick fiddle with it, checked the voltage on the feed at the fridge end and it's only registering 5.5v with the engine running - 0 with the engine off, as it should be - so I suspect the relay's duff.

Haven't got around to tracing the cables back yet, but for those that have tackled this before, where do the relays tend to be? Do the converters fit them in their own idiosyncratic places or does it tend to be an extra relay in one of the Fiat base vehicle fuseboxes?

Scotjimland, you're right about the cable size as well - looks like the converter used what I'd say is 2.5mm2, Dometic manual recommends 6mm2. For the few extra pennies it costs, you've got to wonder why they scrimp on things like this. Running a new cable through will be a right pain in the arse but needs doing if I'm to make it work right.

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[Techno]

Haven't got around to tracing the cables back yet, but for those that have tackled this before, where do the relays tend to be? Do the converters fit them in their own idiosyncratic places or does it tend to be an extra relay in one of the Fiat base vehicle fuseboxes?

Yes

 

[peterc10]

@Feltwell What is your motorhome? Other owners may then be able to help you with the location. I know where mine is on the Hymer.

 

[Feltwell]

Ohh joy. Motorhome is a McLouis. Guess who's likely to be crawling underneath it next weekend working out where the black plastic cable conduit that carries the cable goes! Said conduit is of course identical to 101 other conduits under the van.....

In the unlikely event that another McLouis owner has had the same issue, please pipe up!!

In fairness to McLouis, I've never found it difficult to find where they've put things. Ohh Lord, I've done it now, this one will take hours........

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