Calex Posted August 20, 2012 Share Posted August 20, 2012 Just got back from a very hot weekend away in the Motorhome and noticed when I got home that the ice in the ice cube holders had melted, the fridge had been on 230 volts for a day before we went away, 12 volts whilst travelling and gas once we had set up camp. The fridge didn't seem to be as cold as it normally is whilst on gas but I just put it down to the hot weather amd the lack of shade on the camp site. I will be running some tests during this week, 230volt & gas to see if it seems to be playing up but wondered if this is normal in hot weather? The fridge is a Dometic 3 way unit with manual ignition for the gas and switches for the electric, I did check the pilot light on the fridge on Saturday night and it was alight. Many thanks Steve Link to comment Share on other sites More sharing options...
Tracker Posted August 20, 2012 Share Posted August 20, 2012 Does it freeze OK at night when it is not quite so warm? If so a simple 12 volt fan at the back of the fridge to encourage air movement on hot days might help? When was the fridge exhaust last cleaned and the gas jet checked / cleaned (with air NOT a needle!) or replaced? Link to comment Share on other sites More sharing options...
Calex Posted August 20, 2012 Author Share Posted August 20, 2012 Hi Tracker Thanks for the reply. Not sure if it freezes over night but the ice cube tray had thawed when we arrived home last night around 9.30 but it was still quite warm at that point Not sure how you clean the fridge exhaust so has not been done since I bought the van in June last year, I would say the the gas flame seemed to be burning as well as usual when I checked it through the window in the fridge, thinking about it now there seemed to be daylight visable in the pilot light window which I don't seem to remember seeing before? Steve Link to comment Share on other sites More sharing options...
Tracker Posted August 20, 2012 Share Posted August 20, 2012 They don't usually get as cold on 12 volts as on gas or mains as 12 volts is aimed as more of a 'holding' regime for when you are on the road rather than as a freezing regime. That said we have had plenty of vans that do maintain frozen items on 12 volts! Before you do anything can we ascertain whether gas or mains will or will not freeze down both day and night as I am not sure from what you have said which is doing what? A Google search should point you in the right direction for cleaning but if you do not feel happy or competent to check the jet best get a caravan service business to do it as the jet can be quite tricky to get out and in again depending on how well or badly the access is designed and gas supply is not something to mess about with if you don't have the knowledge! That said - I didn't (still don't) have the technical knowledge the first time I did a fridge jet - but with plenty of experience now of doing it, it is still not a job I relish! Link to comment Share on other sites More sharing options...
Calex Posted August 20, 2012 Author Share Posted August 20, 2012 Hi Tracker My main worry is that the gas didn't seem to keep to fidge as cool as I'm used to but will be checking it out this week when I get a chance, I only noticed the ice cube trays as I was emptying the fridge which I tend to do as soon as I get home so not sure exactly where if any the problem lies. I will google the gas jet before having a closer look to see if I feel comfortable attempting such a job Many thanks for the advice, it is much appreciated Steve Link to comment Share on other sites More sharing options...
WildBill Posted August 21, 2012 Share Posted August 21, 2012 Get a qualified gas engineer to check the fridge if you suspect there is a problem. Peole who do DIY gas work who are not competent to do so are taking a risk, not only to the van but also their partners and children. On top of that, you negate any insurance on the van should there be an accident involving the gas installation. (!) Link to comment Share on other sites More sharing options...
Guest pelmetman Posted August 21, 2012 Share Posted August 21, 2012 Were you level on your pitch?............as our pilot light will be alight but it won't freeze unless level *-)..............Although it gets mega cold on 12 volt especially on a long run :D Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 21, 2012 Share Posted August 21, 2012 The fridge in question is 6 years old and, if its gas-flue has never been cleaned in that time, it would probably benefit from it being cleaned now. Cleaning the flue involves first removing a 'baffle' that hangs inside the flue. This is often impossible to do without first moving the fridge backwards within its housing, or may even need the fridge to be completely removed from within its housing. In such cases, because of the labour costs involved, regular fridge maintenance is often overlooked. A full service by a qualified technician will normally include replacement of the fridge's jet (it's recommended that cleaning the jet should not be attempted) but, if the fridge's gas flame looks OK, it's logical to assume the jet is also OK. Forget GOOGLE-ing - obtain the latest edition of John Wickersham's "The Motorcaravan Manual" (about £12 from Amazon) that includes a subsantial chapter on motorhome refrigerators. Link to comment Share on other sites More sharing options...
bobalobs Posted August 21, 2012 Share Posted August 21, 2012 We have also found our two year old Dometic fridge struggling in the recent hot weather. Have booked it in for a service and have done a bit of research into fitting an auxillary fan. Have found CAK tanks do one which is thermostatically controlled. Has anyone any experience of these and the ease of fitting? Link to comment Share on other sites More sharing options...
Calex Posted August 21, 2012 Author Share Posted August 21, 2012 Thanks for all your replies :-D Wild Bill, I agree with you there and won't be touching anything that I'm not confident on, will start with looking at the flue. Pelmetman, it was a level pitch, I'm not good at sleeping on a slope :-S but I have used it on gentle slope with no problem. Derek, I suspect you are right that it hasn't been looked at since new, all the previous paperwork mentions cooker checks, did it light or not! and damp checks, I have looked into where the nearest Dometic engineer is and will be in touch with them if I need their help. I will be looking for John Wickershams book later today, sound like a good investment. I will be running it on gas later today to see what happens so watch this space :-) Many thanks again Steve Link to comment Share on other sites More sharing options...
Tracker Posted August 21, 2012 Share Posted August 21, 2012 As I understand it, and I am open to correction, an annual habitation check (if done) just lights up the fridge and if it lights it passes. Nothing more - no cleaning or servicing unless it does not light up - so just because a habitation check has been carried out does not mean anything as far as a fridge goes. Link to comment Share on other sites More sharing options...
Calex Posted August 21, 2012 Author Share Posted August 21, 2012 That's how I understood it as well Tracker. I am in the process of running it on gas at the moment so should know later how it fairs, I did notice that the flame was changing in size as I changed the temp setting on the gas side so hopefully that may be functioning ok :-/ Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 21, 2012 Share Posted August 21, 2012 Providing the fridge works properly on one energy source, there is no problem with the refrigeration system itself. All energy sources rely, somewhat counter-intuitively - on heat. The electrical systems, both 230V and 12V, have similar looking heater elements attached to the outside of the main coolant circulating pipe at the rear of the fridge, above the gas burner. The gas burner, and the tube it heats, are visible if the lower ventilation grille is removed. Providing the gas flame is clear blue and steady, it should be functioning as intended, so I wouldn't fuss too much over that initially. If you don't have a user manual for your fridge they can be downloaded from Dometic's website but you will need to know the correct designation for your model. Look inside the fridge for a stick-on plate with serial number and model designation, usually starting RM*************** The next bit will make more sense if armed with this manual. If you run your hand up the rear of the main vertical coolant circulating pipe, you should just be able to touch the electric heater elements. Don't do this if the fridge is running on electricity, or has been recently, because the elements get very hot. If you follow this link http://tinyurl.com/btkv86x and enter your fridge model number etc from the above plate, and then select the correct exploded diagram, it should all begin to make sense. Once you know where to find the electric heating elements, set the thermostat to max, and get someone to turn the fridge on to 230V while you keep your fingers on the two elements. If you feel one getting warm it is working, and you now know which is the 230V element. Turn off and allow to cool down, set the energy source to 12V, and then repeat the above process, this time feeling in for the other heating element, and get someone to start the engine for you and allow it to idle. Again, if all is working OK, that element will begin to get warm to the touch. If one, or other, element fails to heat, you will need to check that electricity is getting to the relevant heater element. Check 230V fuses/circuit breakers are on, and that other 230V equipment fed via the same circuit - often the battery charger - is functioning. Checking the 12V supply is a bit more complicated, because there will be a fuse on the fridge feed, but also a relay that functions when the engine is running to feed power to the fridge, and to isolate it when the engine is turned off. Either may fail, leaving you with no 12V cooling. Beyond this stage, if not competent with electricity, this may be where the Dometic engineer comes in! If competent, you won't need me to tell you how to test the supply. However, you will need the Dometic manual, as above, to identify access to the terminal blocks, and which is which. You may need to move, or remove the fridge to complete these tests. If an element has power, but fails to heat, it is most likely the element has failed. If so, these are available via the above link. If all appears functionally OK, but the fridge is simply failing to cool properly in hot weather, it will probably be the stat, or the installation, that is at fault. Checking the stat is easy, just turn it on on 230V, leave for several hours, and check the temperature with a fridge thermometer. Try removing both ventilation grilles, as these tend to restrict airflow over the evaporator plates. If it stll fails to cool whatever stat setting is used it will be the stat that is at fault, and you'll probably need that Dometic engineer. Have a good look at the back of the fridge and check the top of the riser is nice and hot, and that elsewhere the pipework is cold. Remove dust and cobwebs, especially from the grilles and from the evaporator plates. Uninterrupted airflow is essential, and cobwebs and encrustations of dust reduce efficiency. Now have a good look at the installation section of that manual, and compare it to what you see at the rear of the fridge. Has the sealing been carried out properly, and is that deflector plate present above the evaporator fins? My suspicion is that the answer to both will be no! This is the commonest defect in motorhome (and caravan) manufacture. For these fridges to work properly it is necessary for the warm air at the rear of the fridge to rise freely to create a stack effect. The deflector merely guides that rising air to its intended exit - the top grille. If the deflector is missing, the airflow stalls, so the heat merely builds up, instead of being exhausted. If the heat can't get out freely, it can't draw more heat from within the fridge itself, so the fridge runs warm. If you look at the manual you will also see that minimum and maximum dimensions are specified for the space between the rear of the fridge and the enclosure wall. This too tends to be neglected: too much space and the stack effect can't develop, too little and the airflow is strangled. Usual problem is too much. Rectifying these defects will almost certainly mean removing the fridge to gain access. You can then place battens inside the cabinet to fit snugly to the rear of the fridge, and fabricate your own deflector plate to assist the airflow to the upper grille. If the gap at the rear is excessive, use packing material to bring the gap within tolerances in the area of the evaporator fins. You only need about 150mm above and below the fins, allowing for the finned pipe being angled. Only if all this fails to yield a better performance is it worth fitting fans to the grille, as they are intended to draw air from the void at the rear of the fridge and, if that void isn't sealed to spec, the air will merely infiltrate from elsewhere - usually from inside the van with minimal benefit to fridge efficiency. It may all sound a bit daunting, but is really much more straightforward than the description is to read (or write! :-)) and the result should be a fridge that will perform happily at ambient temperatures well into the upper 80s F, with removal of both grilles getting it by well into the 90s. The internal temperature will rise during the day, but should easily recover at night. The biggest problem when very hot is finding the best stat setting to prevent salad etc freezing at night while staying within safe fridge temps during the day. If very hot, it goes without saying that the best strategy is to park the van so that at least the fridge side is in shade. Hope this helps. Link to comment Share on other sites More sharing options...
thebishbus Posted August 21, 2012 Share Posted August 21, 2012 Another thing to check with these less efficient absorbent fridges, is that the frozen food compartment door is closing properly. When away in the French heat this month my wife said, something wrong with the fridge, the ice cubes are melting. When I checked, I found that the freezer door would not snap shut. This was due to a broken door spring retainer, I did a temporary repair by taping a wedge to the top of the door to keep it closed, this worked. Brian B. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 21, 2012 Share Posted August 21, 2012 Agreed. I forgot that. Also has the same effect if it is very humid and ice has built up around the freezer compartment door, stopping it from closing in a similar way, or if the cooling fins inside the fridge are all iced up, for which it needs de-frosting to get it working properly again. Link to comment Share on other sites More sharing options...
bob b Posted August 21, 2012 Share Posted August 21, 2012 My fridge won't stay alight on gas, but it works perfectly on 12 volt & 240 volts. I'm assuming that its the thermocouple at fault and have ordered a replacement from Leisure Spares.As I've never serviced it I thought as I've removed the grilles and got the fridge half out to get at the thermocouple, I'd service it now. I'm having difficulty locating a suitable flue brush though. Does anyone know where I can obtain a suitable item please? Link to comment Share on other sites More sharing options...
Calex Posted August 21, 2012 Author Share Posted August 21, 2012 Thanks again for all your replies, I'm working my way through various checks at the moment and will let you know how things develop. Steve Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 22, 2012 Share Posted August 22, 2012 bob b - 2012-08-21 10:16 PM ... I'm having difficulty locating a suitable flue brush though. Does anyone know where I can obtain a suitable item please? The Dometic Part Number for a flue-cleaning brush apparently is 0151404001, but you'd best confirm this with a Dometic agent (and also confirm exactly what you'd be getting). Pipe-cleaning brushes are avaiable and I THINK a 3/4"/19mm diameter one would be the right size for a Dometic fridge's flue. The example in this link http://tinyurl.com/cyujv66 has brass bristles and (although steel bristles would be better) should do the job and is cheap enough. The snag would be that it (and anything similar) will be much too short to reach right down a gas fridge's flue, so you'd have to extend it to allow you to push the brush part up and down within the flue. I think the 'proper' Dometic brush (there's a picture in "The Motorcaravan Manual") is much longer, but I'm not certain how flexible it is . Brush flexibility won't be an issue if the fridge has been removed completely from its enclosure, but may be if the fridge has just been moved back a short distance. More expensive steel-bristle brushes, plus extension handles, are shown here http://www.wire-brush.co.uk/wirebrushstore/cat_346933-Cylinder-Wire-Brushes-Extension-Handles.html If there's a company local to you selling tools for domestic oil-boiler cleaning (or you know someone who does such work), you might also try them. This earlier thread mentions flue cleaning and you'll note that I've DIYed a tool to clean my fridge/freezer's long gas-flue. It may not be effective as the genuine Dometic article, but it's good enough. http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=28192&posts=13 Link to comment Share on other sites More sharing options...
Mickt Posted August 22, 2012 Share Posted August 22, 2012 I always turn my fridge stat down when it,s hot during day time and turn it up at night.That,s what i was told to do by a fridge man in spain Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 22, 2012 Share Posted August 22, 2012 However, I'm not entirely convinced aggressive cleaning is required. All the flues seem to suffer is a build up of surface rust and an accumulation of cobwebs. I agree that using a metal brush will best remove the surface rust, but it will in any case return within weeks. As the exhaust effluent is predominantly water, the more the fridge is run on gas, the quicker it will return. IMO, a simple run through with a reasonably stiff nylon bristle bottle brush, followed by a good blow through, will remove most of what needs removal for the fridge to function adequately. With any brush it would be a good idea to protect the gas jet from the fall out while doing this. In fact - but I'm not recommending this as a cleaning method to adopt under all circumstances - the flue (at least all mine have) contains within it a spiral baffle suspended from a wire clip. Just removing the top flue terminal (where present) and lifting the clip to part withdraw the baffle, and then working it up and down fairly vigorously, seems to detach most loose rust, followed by full withdrawal of the baffle to clean it before re-inserting it. All that is really required is a clear airway. It's just a shame that so much at the rear of these fridges is produced from painted mild steel. If they used stainless (so little required the cost would be peanuts) they'd last forever. Hmmmmmmmmmm! I wonder? No, surely not. :-) Link to comment Share on other sites More sharing options...
Calex Posted August 22, 2012 Author Share Posted August 22, 2012 Well I have run the fridge on gas for over 24hrs and it froze the water in the ice cube tray, the general fridge was cool but not extremely cold but as it was empty I wasn't to surprised, will be running it on 230volts once the inside of the fridge has warmed up again :-) Steve Link to comment Share on other sites More sharing options...
bob b Posted August 22, 2012 Share Posted August 22, 2012 Thanks for the links Derek. I've got a compressor and have given it a blast through with compressed air.....after moving the gas jet assembly to one side. I'll source a suitable flue brush tomorrow.I have solved one mystery though. The cutlerly drawer was always the 'hotter side of warm' when the fridge was in use. The baffle plates are in place, but I noticed a gap to the side with allows hot air to to escape into the motorhome via the drawer. Ive got some thin galvanised sheet, so I'll fashion a piece to cover the gap. Link to comment Share on other sites More sharing options...
Guest JudgeMental Posted August 25, 2012 Share Posted August 25, 2012 we are in italy and temps 35-40+ deg C. I find fridge hopeless on electric and run it on gas which works much better...Why is this? I also hang a desk top fan on grill which forces air over the rear elements and works a treat! proper cool drinks. We had the CAK twin computer fan contraption on an earlier van but it would not fit on last van...they work very well. It is now in bits and not responding to first aid so have not fitted it to current van.... Are the electric absorption fridges better ...and why is this please? Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 25, 2012 Share Posted August 25, 2012 Your fridge is an absorption fridge, the others are compressor fridges. Both suffer in extreme heat, depending the temperature zone they are designed for. Most fridges fitted to caravans and motorhomes are for temperate zones, so are a bit over-cooled in very cold weather (lettuce lollies, anyone!) and struggle in very hot weather. Best boost for performance on hot days is to remove both grilles, which allows better airflow over the evaporator fins. It generally achieves better than the fans and, since the problem is only occasional, is a good, cheap, workaround. It is worth checking that the correct clearance around the rear of the fridge has been achieved, many have far too wide a gap at the rear, meaning the "stack" never works properly. All fridges do is take heat from the air in one place and deposit it back into the air in another. If the air into which the fridge is trying to dump its heat is already hot, its efficiency falls. Doesn't matter what kind of fridge it is, physics rules, OK? To get rid of that heat you either need cooler air, or more air. Fitting aircon at the back of the fridge is a bit self-defeating :-), so anything that accelerates air movements over the hot bits helps. The external grilles get in the way, and are not particularly efficient - especially with their insect screens - so taking them out altogether allows the fridge to perform at max efficiency. Why gas works better is probably because the gas on max achieves higher temperatures under the thermo-syphon than the electric element can achieve, so the cooling system runs faster, plus, at a guess, the gas flue being also hot, accelerates the cooling airflows a bit into the bargain. The problems with most compressor types are a) noise (the compressors are not silent), and b) that they are seldom provided with adequate ventilation, so all the heat gets dumped back into the van, making the van that bit hotter, which is somewhat self defeating. They would all benefit from being vented in much the same way as absorption fridges, but they are inherently more efficient in converting energy into coolth. However, since (in vans etc) they only run on 12V electricity, they have a significant battery drain when not on EHU and, unless they can get rid of their heat, they will still struggle on very hot days. Grilles out! :-D Link to comment Share on other sites More sharing options...
Vernon B Posted August 25, 2012 Share Posted August 25, 2012 A simple thing that transformed the performance of our Dometic fridge was tightening up the aluminium heat transfer fins at the rear inside of the fridge. You can do this in seconds with a suitable socket spanner. I'm indebted to Martin Beer at Sylmar Services Limited for this tip. Sometimes its the simple things that lie at the root of these problems. Brian also fitted the Dometic twin cooling fan for me. That has only made a marginal difference to the heat build-up behind the fridge although it should have been a standard fitment.. For an international outfit it 's surprising that Dometic appear to be totally unaware of the temperatures that can be experienced abroad. That goes for their Heki roof lights as well as fridges. V Link to comment Share on other sites More sharing options...
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