Thetford Fridge

[milliemop]

Recently bought a 2004 bailey Pageant, and have found out that the fridge is not working on 12v (240 is ok) either from the car when travelling or the van on site--have checked out the wiring and fuses, all ok----I thought maybe I am not giving the fridge long enough to cool but I travelled down from the north east to home which took about 3 hours and the fridge was starting to defrost by the time I reached the house---thinking now that the 12v heater may have packed up---anyone had a similar problem?

 

[RogerL]

The fridge 12v circuit will only work from the car when the engine's running. It'll only work on 230v or gas, not 12v, when on site. All caravan fridges are designed that way.

Check out the connections at the car 12S socket, with the engine running. A multi-meter across pins 6 & 7 should read 14v. If that's ok, use the handbook to identify the fridge 12v connections at the relay unit and check that 14v is available, with car connected and engine running. There are fuses in the relay unit so check those.

 

[Guest]

12V is not really man enough to actually cool the fridge, it will merely keep an already chilled unit cool while travelling. You really need to check you are getting power to the fridge itself when the engine is running, at quite high revs. This can be difficult as the connections are usually hidden in the back. However, if you can find the wires and do get a good voltage, then it is possible the element has blown. You will need to get a dealer to replace it as the fridge has to come out, and Thetford ones are not designed to be owner friendly.

 

[RogerL]

12V is not really man enough to actually cool the fridge, it will merely keep an already chilled unit cool while travelling. You really need to check you are getting power to the fridge itself when the engine is running, at quite high revs. This can be difficult as the connections are usually hidden in the back. However, if you can find the wires and do get a good voltage, then it is possible the element has blown. You will need to get a dealer to replace it as the fridge has to come out, and Thetford ones are not designed to be owner friendly.

The 12v circuit is the same power as the 230v, about 96 watts - there's no difference in their cooling power.

A caravan fridge will only cool down, from ambient, quite slowly what ever power source is used so it's best to run the fridge for 24 hours before expecting proper performance. Where practical just turn the fridge on, with 230v, for 24 hours before you load the fridge and go away.

 

[milliemop]

disagree with you scotch lad----on my last van when travelling the fridge would cool down to almost to making ice--I later found out that there is no thermostaic control when connected to the car, so the temp. just keeps dropping, and dropping--the only difference with this new van is it has a thetford fridge, and not an electrolux, maybe I am "losing" voltage somewhere, anyway----I have altered my 12s pin to suitnew van configs and there is power there so further investigation is required

 

[sparkes]

the fridge on my Bailey only activates at 12 volts when connected to the car, the engine running and the car/van switch set to van

if you have done all that then you need to check the socket on your car, I seem to remember the wiring Changing in 2000 (ish) so if you old van was older than that then you may need the plug wiring swapped

Steve

 

[milliemop]

the fridge on my Bailey only activates at 12 volts when connected to the car, the engine running and the car/van switch set to van

if you have done all that then you need to check the socket on your car, I seem to remember the wiring Changing in 2000 (ish) so if you old van was older than that then you may need the plug wiring swapped

Steve

thanks steve---but had my wiring altered at the socket---I think what may be wrong is the thickness between the wiring on the car and the van----at the car's socket it looks really thin (2.5 amp) where as at the van's plug it is much thicker (10amp+)----would this cause a sudden voltage drop??? ----also I don't have the car/van switch system, just switch the fridge to battery mode, and the charging unit off.

 

[MikeP]

Once you've confirmed that power is reaching the fridge, you need to connect an ammeter to check whether the fridge is actually drawing any power.

I'm a bit worried about the size of your 12S wiring. I once had a "cheap" Witter towbar fitted, and later discovered that they had cut corners by using dirt cheap low quality 12N and 12S cable. I won't do that again. If your cable isn't the right stuff, you will need to rewire. Until then you can't expect your fridge to work.

My caravan doesn't have a habitation relay, so I can do the following simple test. With the engine running at about 2000 RPM I switch on one of the internal 21W lights. I then switch on the fridge, and the 21W light dims a little. This shows that the fridge is using power rather than just having power available to it. Obviously I don't know how your van is wired, but it might be worth trying this once you have beefed up the wiring.

 

[Guest]

I can only quote Thetford's own manual whch states that the fridge should always be cooled using either Mains electric, or gas. It also clearly states the freezer compartment is unsuitable for freezing food, it will only keep pre frozen food in that state. That is a bit curious as it will make ice. The 12 volt system will only maintain the temperature if the engine is running. This means when the engine is off, or at idle the fridge is technically defrosting, and is not expected to 'catch up' too much. I have always found that if it is very well cooled prior to the trip, and the door is not opened, then it will survive quite a while, but I am sorry, I have yet to see a 12 volt device that will freeze. Any 12 volt in-car fridge I have seen always states that the maximum temperature drop that may be expected is 18-20 degrees below ambient. That means if you are in the Med and the outside temp is 35 degrees then your fridge will get to 15 degrees centigrade. That is not freezing.

Thetford don't actually give the power ratings for 12 volt but for 230 volt the unit is pulling nearly 12 amps, which is a lot higher than what you would hope to get from 12 volts.

Like any freezing device it depends on the ambient temperature. Thetford use a 25 degree C value which is fair enough, but will be insufficient in the Med where you really need the thing.

 

[MikeP]

I once tested a fridge (not in a caravan) by connecting it to a fully charged car battery. The evaporator had ice crystals on it after about 2 hours. I'm not saying that it would have frozen food, but it certainly caught the moisture in the air and froze that.

When we set off on our hols we put a 2 litre bottle of ice in the bottom of the fridge, wrapped in a teatowel. Last summer we left home at 0500, caught the 0800 out of Dover, landed 1100 CET and reached our first site at about 1600 CET. It was a fairly cool day, and the ice was still ice. Our lasagne was still frozen, so we had to eat it the next day.

I think I've gone off topic a bit.

 

[RogerL]

Scotch Lad - I think you, or Thetford, have got your numbers muddled. 12A at 230V is 2.76KW - I don't think so, more like 12A at 12v.

The Electrolux (Dometic) RM4270/1 which preceded the Thetford was rated at 125watt on 230V and 120watt on 12v. These are the same for practical purposes, although as rob pointed out, the fridge will get COLDER on 12v as there's no thermostat. I would expect the Thetford to be broadly similar.

 

[RogerL]

Thetford's advice to cool the fridge down on mains electric or gas is correct - it's best to allow 24 hours - this is in a stationary position so you wouldn't expect to use 12v!

Once in use, 12v cooling is just as effective as gas or 230V.

 

[Guest]

I would point out that both Dometic and Thetford state that their fridges should not be used to freeze food. A bit curious about that as they will make ice, and happily keep pre-frozen food.

Again, the efficency of an adsorbtion fridge is very dependent on the ambient temperature, all their quoted figures are based at ambients of 25 degrees. Now either I have just been unlucky but I have owned at various times Electrolux(2), Dometic and now Thetford fridges . I also own a Camping Gaz 3 way portable fridge. None of them has ever worked as efficently on 12 volt as they do on gas or main electric, and in the Med they all struggled. It was only during the night that ice could be made easily. I also tried a 12 volt fridge and ran it contimously using a charger. Putting a thermometer inside the unit revealed indeed a drop of 20 degrees from ambient, as detailed in the instructions, but when it was 35 degrees outside that still meant 15 degrees inside the uni, so not much use. In fact we are now looking at taking a small compressor fridge as it will work much better than any adsorbtion unit, at higher ambient temperatures. Looking at our European cousins, this appears to be the way they are following, so I am always willing to learn.

Yes, in the UK they work fine, especially up here in the cold north, but I like the sun and heat too much.

 

[RogerL]

Compressor fridges have always been more efficient and more effective than absorption ones but they can't work on gas. A number of motorhomes seem to be built with domestic compressor fridges, or fridge-freezers.

 

[Guest]

The first time I really came acros them as standard equipment was on our 'once in a lifetime' trip to Oz in 2004. We hired a motorhome to tour around for a couple of weeks and it came with a compressor fridge. I admit at first the noise did keep us awake, but after the 3rd night it was unobtrusive, and we slept like'babes'. The greater efficiency was also noticeable, especially in Oz heat. Yes, you needed mains power, but that was taken as a 'given' in that country. Anyway you also needed mains for the AC, which was a domestic type unit. This was all in a medium Transit van body, so I was impressed.

I suppose it comes down to priorities. In Oz cooling the beers takes precedence over anything else??

 

[milliemop]

I can only quote Thetford's own manual whch states that the fridge should always be cooled using either Mains electric, or gas. It also clearly states the freezer compartment is unsuitable for freezing food, it will only keep pre frozen food in that state. That is a bit curious as it will make ice. The 12 volt system will only maintain the temperature if the engine is running. This means when the engine is off, or at idle the fridge is technically defrosting, and is not expected to 'catch up' too much. I have always found that if it is very well cooled prior to the trip, and the door is not opened, then it will survive quite a while, but I am sorry, I have yet to see a 12 volt device that will freeze. Any 12 volt in-car fridge I have seen always states that the maximum temperature drop that may be expected is 18-20 degrees below ambient. That means if you are in the Med and the outside temp is 35 degrees then your fridge will get to 15 degrees centigrade. That is not freezing.

Thetford don't actually give the power ratings for 12 volt but for 230 volt the unit is pulling nearly 12 amps, which is a lot higher than what you would hope to get from 12 volts.

Like any freezing device it depends on the ambient temperature. Thetford use a 25 degree C value which is fair enough, but will be insufficient in the Med where you really need the thing.

as you say scotty, on this type of fridge the outside temperature dictates how efficient the fridge will perform, but remember that when you are towing the movement of air over the evaporator is much greater allowing the unit to work well----this is of course if the fridge has been installed correctly ---lots of people have now fitted a small extraction fan onto the top vent to do exactly the same thing when on site