Fridge not Working on 12V

[CheapnCheerful]

Might be a difficult one this!

An old electrolux fridge. Works fine on Gas and 240V. It seems to operate poorley - if at all on 12V. It is difficult to tell if it is completely non-working as I have not really done a comprehensive test.

The situation is that depite being pre-cooled on gas overnight, after a 4 hr journey fridge is considerably warmer - to the point that it feels like the contents are keeping the fridge cool rather than the other way around!

The thing is the electrical side checks out OK, removing the 12V fuse to the fridge and putting an ammeter accross the terminals shows the expected 8 or 9 amps draw from the car. This suggests that the 12V element is working correctly.

I did once try the fridge on 12V from warm, and after 5 mins there was no noticable reduction in temperature - even on 12V I would have surely expected at least some signs of coolness in the ice making compartment at least?

Is it possible for the heating element to become detached from the 'boiler' part of the circuit and thus be working but not heating the refrigerent?

Any other ideas?

 

[rob_jax]

The power rating of the 12 volt and 230 volt heaters is identical - so operating the fridge on either power source should provide the same cooling efficiency.

The fridge really should work as well on 12 volts as on mains - and indeed ours does perfectly on 12 volts.

But I can think of at least three reasons why you may be having problems:

1. Assuming your ammeter is halfway competent product, then the 8 or 9 amps may be the issue. I would have expected a current closer to 10 amps, and this may mean there is a voltage drop in the wiring or in the car to caravan connector. And this will reduce the performance considerably.

Is all the fridge wiring at least 30 Amp rated? Is the connection to the car as good as it can be?

2. The 12 volt heater cartridge might have become dislodged in the chimney - and need repositioning (and the chimney cleaning if you've used it on gas for some time)

3. Since the fridge only works on the car 12 volts when the engine is running above idle speed - this means that the you're usually towing for this to happen - and it may be that your fridge installation isn't working properly with air flowing past the vents.

Is the fridge sealed from the interior of the caravan? Do you feel draughts from the fridge vents when sitting in the caravan? Is the space behind the fridge as small a space as it should be?

Robert

 

[CheapnCheerful]

Many thanks for your reply.

1. The element fitted to my fridge is rated at 95W according to the manual. Since 8 amps at 12V = 95W, I feel reasonably confident that it is getting enough voltage. OK If the wiring was 100% it would perhaps be seeing 13.5 Volts or more with the engine running, but since it seems to be drawing its rated current it should work reasonably well on that basis.

2. This sounds like the most likely problem - but is it something which is known to occasionally happen? If so then I expect I will need to take the fridge out to check?

3.The relays on the car are standard automotive, not the voltage switching type. Whenever the ignition is turned on, the relays are energised. The only exception is that they are de-energised when cranking the engine to avoid accidentally drawing a high current from the van battery. This means that there is no issue with the fridge supply dropping out when idling. All the wiring in the car is 30 amp rated, with seperate wiring for van battery and fridge. Not sure about the van, but it looks reasonably thick, and is probably the original manufacturer installed wiring so should be OK.

The fridge has both vents to the inside and outside, so it is quite possible that it is subject to draughts. However I would have thought this would only be an issue when running on gas?

The space as small as it should be? Well I expect it is as per original installation, but I would have expected that too small a space - inadequate room for air circulation, would be worse than too large a space. I would expect the fridge to work on 12V even if it was outside - ie space behind it infinite !

 

[Carli_374365147]

There are 2 ways of getting a fridge down to temperature.

Gas and Mains Electric.

The 12v system is NOT designed to chill your fridge down, just to maintain it.

I knew this already, but when we picked up our new van, the dealer when doing the handover of the caravan also told us about the 12v only being to maintain the coldness in the fridge. He said that mains or gas should be used to chill it down for at least 24 hours before a trip.

This is what we have always done.

On a recent trans European trip, it was noticed that the fridge is no where near as cold when runnign from the cars 12v supply.

And thats on a brand new fridge!

 

[rob_jax]

Hi CnC,

I agree with your power diagnosis - your meter readings sound right for a 95 watt heater - I was expecting a 110 to 125 watt heater for a Dometic.

The heater cartridge is often simply held in place with something like a cable tie, so yes, they can slip and change position.

If you don't already have a copy, then the Haynes Caravan manual is a good buy at around

 

[Guest]

On this topis does anyone know how to check if a Thetford Norcold fridge is working on 12 volts, apart from the obvious, that is it stays cold?

I am not 100% sure mine does but I am also not too sure about checking the 12S plugs and sockets as Witter did advise me that many tow electrical systems will only work when the load, namely the trailer, is actually attached. Using a meter on the tow plug does nothing. So I am looking for a test point downstream of the hitch. Talking of Thetford fridges, does anyone know how to actually remove one? There are no obvious fixing screws.

 

[simon_374395949]

On this topis does anyone know how to check if a Thetford Norcold fridge is working on 12 volts, apart from the obvious, that is it stays cold?

I am not 100% sure mine does but I am also not too sure about checking the 12S plugs and sockets as Witter did advise me that many tow electrical systems will only work when the load, namely the trailer, is actually attached. Using a meter on the tow plug does nothing. So I am looking for a test point downstream of the hitch. Talking of Thetford fridges, does anyone know how to actually remove one? There are no obvious fixing screws.

the 12volt system on the 3 way fridges is really just to keep them working on the move..there is so many factors involved in the 12 volt feed that a tiny drop in voltage makes a huge difference to the cooling on the fridge..in fact there pretty bad as you have noticed

best way is to run a small inverter from the main battery connected to it comes on with the engine running then run the fridge on the 230 volts from the inverter while on the move..hey presto 100% cold fridge again..the inverter can be wired into your 230 volt rcd/mcb's and fitted with a change over switch so the inverter will then feed through the main 230volt panel..just remember to leave all the items switched off when on the move

you can also wire it through a realy with auto realy which switches when 230 volt is present..it should really be done by a qualified person...you do this at your own risk!! which means if you blow youself up dont try and take me to court!

small 300 watt inverters are fine for pretty much most fridges..check the rating and allow a little extra on top

compressor type fridges require a pure sine wave inverter otherwise damage will accur, 3 way type ones will run on the cheapo inverters no problem

hope that helps..

ps..dont blow your self up!..if in doubt get a qualifed person to sort it

 

[Steven_374406970]

On this topis does anyone know how to check if a Thetford Norcold fridge is working on 12 volts, apart from the obvious, that is it stays cold?

I am not 100% sure mine does but I am also not too sure about checking the 12S plugs and sockets as Witter did advise me that many tow electrical systems will only work when the load, namely the trailer, is actually attached. Using a meter on the tow plug does nothing. So I am looking for a test point downstream of the hitch. Talking of Thetford fridges, does anyone know how to actually remove one? There are no obvious fixing screws.

Help!!

I bought a 2nd hand Electrolux 3 way fridge for the camper conversion Im doing. Problem is I moved all the controls from the top to the side about 6 mths ago and cannot find the diagram I made for the wiring. It is an old fridge and I cant find anything online to do with its wiring.

It has a rocker switch which has the off in the middle and 12V/240V either side. In addition there is the temp dial which I think is also part of the circuit. Can you help?

Steve