Fridge problems?

Ron's Technical Tips number -10 degrees

FRIDGE PROBLEMS

It's the time of year when our vans come out of storage and many of us have fridge problems.

What most of us have to remember is that our fridges are quite often original, and that makes them over 20 years old. Not many home appliances last that long, so it's not surprising that we get a lot of fridge problems.

Here in very simple terms is how your fridge works. At the back there is a chimney. At the bottom of the chimney is a gas burner, heat from the flame goes up the chimney and passes into the tubes that contain a chemical, which converts the heat into cold - very simple explanation.

Also in the chimney are two heating elements - one powered by 240v and the other by 12v. So there are 3 possible sources of heat to heat up the chemicals.

The commonest problems are the fridge not working on any of these 3 sources, so we will discuss each one in turn.

Gas. The commonest fault is that soot and or crap falls down the chimney and onto the burner which either restricts the flame, or preventing it lighting at all. This is quite easy to fix, as long as you can get access to the burner assembly, usually but not always through the lower ventilation panel outside.

The next problem with gas is that it won't light. It acts just like a cigarette lighter - you press the button, the gas is switched on, and a spark ignites the gas. However unlike a cigarette lighter, when you take your finger off the button, the gas should stay ignited. This is because there is a safety feature called a thermocouple. This is a little finger of metal that is placed in the flame, and if it gets hot, as it should, then it operates a gas valve that keeps the gas flowing. If the gas goes out, it cools, and shuts off the gas. If the gas lights, but goes out when you take your finger off the button after about 20 seconds, then it is usually the thermocouple. The thermocouple is a fundamental safety feature.

The next problem is no spark. When you try and ignite the fridge there is usually a tick tick sound which is the spark. There is another little finger of metal placed in the burner that allows the spark to jump between it and the burner body, again just like an electronic cig lighter. If there is no power getting to this, or the spark can't jump because of crap and soot in the burner, then it won't light.

Finally - there just might not be any gas at all! After storage with the gas turned off, there may be no gas in the pipes, or it might take a while to come through. You have to be patient. Sometimes it's a good idea to light the cooker to promote the gas flow through the pipes, and do remember to make sure all the relevant gas valves are open.

Electricity. Both 12v and 240v elements work on the same principle - just like a kettle element. Power is applied and the element gets hot. Other than making sure the fuses are OK, there is very little to go wrong and if it doesn't work then usually the element has given up the ghost and needs replacing. Occasionally you get a faulty switch, which can be hard to troubleshoot without access to the back of the switch and the use of a multimeter.

Don't forget that in a correctly wired van, the fridge will only work on 12v when the engine is running. If everything else works fine, but you are not getting cooling while driving, assuming it is actually switched on to 12v, the the commonest reason is that the relay which switches 12v from the engine alternator to your fridge is broken. This relay is usually to be found behind the main habitation fuse panel. You should also remember that the 12v element is the weakest of all the heat sources, so the fridge will be less cool when driving than it will be on gas or 240v.

If the fridge is working but not getting cold, or just getting cold at the top, near the freezer box, then this usually means the chemicals have got separated in the pipes. There are various techniques to try and fix this and Peter Curry is our resident expert. 

There are plenty of how to fix videos on Youtube and lots of previous posts on this group, if you are a DIYer, and we have resident experts and recommended engineers to help you out if you are not.

Don't mess with gas unless you know exactly what you are doing - it is quite an easy job to clean rubbish away from the burner, but anything that involves undoing actual gas fittings or pipes should be done by a trained gas man. Replacing elements is also quite a tricky job.

Finally - we all like to keep our vans original, but fridge problems are one of the commonest problems we find on the group. A temperamental fridge can ruin an otherwise perfect summer trip. Nothing lasts forever, so sometimes it's just best to chuck in the towel and buy a new fridge. The new Dometics are a lot better than their grandfathers, colder and more efficient. I gave in and bought a new fridge last year and we love it. But they ain't cheap! But don't give in unless you have had a proper opinion from an expert.

Stay cool people!

UPDATE - more information about the absorption mechanism by Peter Curry

Never turn your fridge upside down it will just pour all the sludge from the resevoir into your evaporation jet. what people are trying to do when they do this is to remix the chemical cocktail that is the driving force that makes your fridge cold.

There are much easier methods to try first , with fridge removal being a final option ready for rotating the fridge to mix the cocktail.
And even this is done in a prescribed manner and direction.
PLEASE DO NOT REMOVE YOUR FRIDGE AND STAND IT ON ITS HEAD you are taking a chance with the odds being about 35% for you and 65% against you.

If fridge has been stood for a while and will not get cold after being on on gas for 24hrs with good flame and flue then there are two possibilities.

1 the fridge is no good buy a new one
2 the chemical cocktail that runs the fridge has sperated out

These are chemicals that once mixed live reasonably happily in a cocktail but once seperated need some encouregment to join to gether again.
Put fridge on gas and if not single energy selector type, put the mains on as well and turn both to full, leave for 4 to 6 hours then turn fridge to 12v and take the van for a drive down a rough road - you are looking for vibration not bloody great potholes! About 1/2 hour is enough,
Then go home put fridge on gas and leave over night.
We have a 90% success rate with this.