- Sep 2, 2025
- 1
- 14
- Funster No
- 114,934
- MH
- Cheyenne 686G
I thought I might post this for the benefit of other users
I have a Dometic 74xx fridge, about 18 years old in my Autotrail campervan
A few summers ago it began to play up. The fridge was getting hot inside and smelt somewhat when it was shut. It can quickly ruin a trip, that's for sure. I did a lot of internet trawling to find a solution. Along with the usual horror stories, people telling others 'not to touch it unless you're qualified', others saying 'get a compressor fridge' and so on, I concocted a plan which I put into action. The long story short is I got it going again and it even works better than it did for several years before it started 'stalling' as the 'warm inside, only hot on the ammonia/water separator but cold on the ammonia condenser' (for those that are technical) condition is known.
To save some reading this is about what to do when it really goes wrong and all the simple things have been ruled out. It's not about checking burners, checking ventilation, power, fridge door seals and all of that - I will assume any competent person will have done those things already and, most of the time, they work, particularly the burner flame which seems to be a favoured home for spiders which then get incinerated and block it. This is for when all that is working but the fridge won't cool and even gets hot inside rather than cold.
The problem - it seems - is that the tri-mix (ammonia/water/hydrogen) that makes up the cooling fluid in a three-way absorption fridge is prone to crystallisation and corrosion after long periods. To prevent this manufacturers add chemicals to the fluid to slow these processes as when they occur they can block the many channels and pipes that allow the fridge to function and this causes the 'stall' and subsequent fridge failure. The trouble is that over many years, particularly if the cooling mixture is not being constantly circulated because it's not being used, the chemicals can separate out of the fluid and crystals start to form along with some corrosion as the cooling unit is made of steel and one of the components of the mixture is water. The pipes then become either blocked or have insufficient flow-rate to allow the fridge to work.
My solution
1/ I initially removed the fridge and turned it upside down and back over again several times, leaving about 30 seconds between turns. The idea being that this would swirl up the mixture, wash away any light corrosion and restore circulation. The fridge makes a marvellous gurgling and burping noise as it's turned over, a bit like Victorian plumbing in an old house when you flush a loo...
2/ It worked! But only for a while. After a few weeks the stall occurred again and I started looking at new fridges (about 1200 euros, ouch!) or compressor conversions and so on....
2/ Not wishing to admit defeat, I removed the fridge again and this time inverted it perhaps 20 times to give it a really good swirl up
3/ I then got a detail sander - the small electric triangular ones for woodwork - took off the sandpaper so it was just the rubber triangle part and laid the fridge on it's door so I could get to the back of it and then used the vibrating edge of the triangle to really 'buzz up' all the pipes, condensers and other parts on the back of the fridge. You have to find the sweet spot, it's one of the back corners of the triangle, and this really vibrates the metal it is touching (and makes a very loud noise to boot!). The idea being that the intense vibration would knock off any corrosion and smash up any crystals inside the cooling unit. It took about half an hour.
4/ I then repeated the invert procedure another 20 times to swirl up whatever I'd managed to knock off the inside of the pipes and condensers and to give all the pipes a good flush through
5/ Once replaced the fridge was as good as new and it's still going 4 years later. If anything it now cools a bit too much, especially on gas, and I'm 1200 euros better off.
Getting it out was a pain, it was a two man job, and if I did it again I'd put some carpet or an old curtain down on the camper floor because the fridge has some sharp edges and these marked the lino floor of the van as I turned it over repeatedly. But overall the operation was very successful and saved a bunch of money plus meant a repairable and quite polluting item was not consigned to landfill. After I got it going again I invested in some new hinges for the freezer door (the old ones had cracked) and some new seals and internal parts and I think it may well go another ten years before being looked at again, if the motorhome is still being used then.
I suspect this problem is quite common after a few years especially in lightly used fridges, so I hope this might prove useful to another person like me who was pulling their hair out with frustration. Cheers to all...
I have a Dometic 74xx fridge, about 18 years old in my Autotrail campervan
A few summers ago it began to play up. The fridge was getting hot inside and smelt somewhat when it was shut. It can quickly ruin a trip, that's for sure. I did a lot of internet trawling to find a solution. Along with the usual horror stories, people telling others 'not to touch it unless you're qualified', others saying 'get a compressor fridge' and so on, I concocted a plan which I put into action. The long story short is I got it going again and it even works better than it did for several years before it started 'stalling' as the 'warm inside, only hot on the ammonia/water separator but cold on the ammonia condenser' (for those that are technical) condition is known.
To save some reading this is about what to do when it really goes wrong and all the simple things have been ruled out. It's not about checking burners, checking ventilation, power, fridge door seals and all of that - I will assume any competent person will have done those things already and, most of the time, they work, particularly the burner flame which seems to be a favoured home for spiders which then get incinerated and block it. This is for when all that is working but the fridge won't cool and even gets hot inside rather than cold.
The problem - it seems - is that the tri-mix (ammonia/water/hydrogen) that makes up the cooling fluid in a three-way absorption fridge is prone to crystallisation and corrosion after long periods. To prevent this manufacturers add chemicals to the fluid to slow these processes as when they occur they can block the many channels and pipes that allow the fridge to function and this causes the 'stall' and subsequent fridge failure. The trouble is that over many years, particularly if the cooling mixture is not being constantly circulated because it's not being used, the chemicals can separate out of the fluid and crystals start to form along with some corrosion as the cooling unit is made of steel and one of the components of the mixture is water. The pipes then become either blocked or have insufficient flow-rate to allow the fridge to work.
My solution
1/ I initially removed the fridge and turned it upside down and back over again several times, leaving about 30 seconds between turns. The idea being that this would swirl up the mixture, wash away any light corrosion and restore circulation. The fridge makes a marvellous gurgling and burping noise as it's turned over, a bit like Victorian plumbing in an old house when you flush a loo...
2/ It worked! But only for a while. After a few weeks the stall occurred again and I started looking at new fridges (about 1200 euros, ouch!) or compressor conversions and so on....
2/ Not wishing to admit defeat, I removed the fridge again and this time inverted it perhaps 20 times to give it a really good swirl up
3/ I then got a detail sander - the small electric triangular ones for woodwork - took off the sandpaper so it was just the rubber triangle part and laid the fridge on it's door so I could get to the back of it and then used the vibrating edge of the triangle to really 'buzz up' all the pipes, condensers and other parts on the back of the fridge. You have to find the sweet spot, it's one of the back corners of the triangle, and this really vibrates the metal it is touching (and makes a very loud noise to boot!). The idea being that the intense vibration would knock off any corrosion and smash up any crystals inside the cooling unit. It took about half an hour.
4/ I then repeated the invert procedure another 20 times to swirl up whatever I'd managed to knock off the inside of the pipes and condensers and to give all the pipes a good flush through
5/ Once replaced the fridge was as good as new and it's still going 4 years later. If anything it now cools a bit too much, especially on gas, and I'm 1200 euros better off.
Getting it out was a pain, it was a two man job, and if I did it again I'd put some carpet or an old curtain down on the camper floor because the fridge has some sharp edges and these marked the lino floor of the van as I turned it over repeatedly. But overall the operation was very successful and saved a bunch of money plus meant a repairable and quite polluting item was not consigned to landfill. After I got it going again I invested in some new hinges for the freezer door (the old ones had cracked) and some new seals and internal parts and I think it may well go another ten years before being looked at again, if the motorhome is still being used then.
I suspect this problem is quite common after a few years especially in lightly used fridges, so I hope this might prove useful to another person like me who was pulling their hair out with frustration. Cheers to all...
