Dometic RM8550 Misbehaving on gas

[Grubber 12]

I have a 2008 Bailey Senator with a Dometic RM8550 3 way fridge that is playing up on gas. The fridge has a manual ignition with a new AAA battery installed; it sounds like it is sparking well.. It has a needle gauge where the needle should swing in to the green zone when the fridge is working correctly on gas. It may also be worthy of note that the caravan has been stored for some time without use; in fact it is quite possible that the fridge has not been used on gas for years; possibly even ever. I have 2 issues: 1. it is temperamental to get running on gas, and 2. It does not appear to be running cold enough.

Initially the fridge would not fire up on gas at all. So I purged all the gas lines by burning on all of the other gas equipment. Then eventually I got it lit. The needle on the gauge slowly swung across so that it was just (and only just) touch the green zone. I left the fridge running overnight with 2 small freezer blocks in the freezer compartment. In the morning they were not fully frozen. And there was drips of water in the fridge compartment. So here is my first issue: when I do get the fridge running on gas it does not appear to be cooling enough.

The second issue is that it does not always fire up on gas. Most of the time I hear the spark and then the ignition of the gas, I continue to hold in the knob for 15 seconds (as instructed in the manual), but it appears that the flame must have petered out. Then other times it does not light at all.

So in summary; gas supply to the fridge is good, spark is good. Sometime the fridge will not ignite, sometimes it will light temporarily and on the the occasions that it lights and satay lit it does not appear to be running cold enough.

Any advice from you experts will be greatly appreciated.

Sorry for the long post but I wanted to make it clear what the problem is.

 

[Jcloughie]

I just Googled ‘Dometic RM8550 gas jet’.

New assemblies are available at a price. Also YouTube advice from people with similar problems.

Worth a look.

John

 

[ProfJohnL]

I strongly advise you have the fridge serviced. At 16 years old and if the gas side has not been regularly used , the burner can rust which means the flame pattern is incorrect, and it could be ejecting a flame in the wrong direction, or insects may have got into the assembly and may be blocking the venturi preventing the gas and air from mixing correctly.

With the age of the fridge, I don't know if the correct spare parts will be available.

In common with all gas appliances , if you are not able to complete the work in accordance with the regulations and standards , then you should refer all installation , non user maintenance , removal, repair and re installation and recommissioning to a certified professional.

 

[RogerL]

I strongly advise you have the fridge serviced. At 16 years old and if the gas side has not been regularly used , the burner can rust which means the flame pattern is incorrect, and it could be ejecting a flame in the wrong direction, or insects may have got into the assembly and may be blocking the venturi preventing the gas and air from mixing correctly.

With the age of the fridge, I don't know if the correct spare parts will be available.

In common with all gas appliances , if you are not able to complete the work in accordance with the regulations and standards , then you should refer all installation , non user maintenance , removal, repair and re installation and recommissioning to a certified professional.

Agreed - I've had similar issues despite my caravan/fridge being serviced every year as the gas fridge is only used during the service - apart from the one night/year off EHU !!!

 

[Anseo]

I trust that this may help:

Download the PDF file from this link

The fridge is quite easy to work on if you remove it from its fixed location, not in itself a difficult job but time consuming.

I found that parts were in the 'rip-off' price category from a lot of the main parts suppliers.
I could not obtain gas heating element, 230v heating element or 12v heating element at realistic prices and was forced to be shafted for same.

Some parts can be found easily at realistic prices, e.g. universal thermocouple £10 delivered -as opposed to £50 odd plus delivery from many suppliers.

What the attached diagram describes as 'magnet insert' ( I knew it as something else but cannot remember right now - it allows the gas to continue to flow after the igniter button is released and was the main reason for my fridge not performing properly), I suggest you replace it if you are going through a fridge overhaul routine.

'Magnet Insert' from main suppliers will be in excess of £80 from most of the obvious parts suppliers, but the same component can be had for less than £10 delivered.

I purchased a gas detector and gas leak detector spray and proprietary gas pipework sealant(s) and a manometer etc.

Take careful note of the placement of all fittings and installation items (foam room sealers and fittings), a camera is your friend here, take plenty of picures from various angles.

Safety being your prime concern.

 

[woodsieboy]

Sorry to sound a doomster but we recently had a new caravanner on here who had fridge problems on gas and ended up having a fire. I would follow the advice from Prof John and get an authorised servic agent to sort it for you.

 

[ProfJohnL]

The Gas Safety (Installation & Use) Regulations, (GSIUR) is normally the "bible" when it comes to working on gas appliances or installations in the UK, and they cover virtually all installations.

There is a specific exemption clause in the GSIUR where it allows:
The private owner of a touring caravan or self propelled motor home. provided the vehicle is not used as part of a business, or is not rented or not loaned out, is allowed to undertake work on the gas installation and appliance in the vehicle, without needing official authorisation as required by the rest of the GSIUR.

However whilst the private owner may be allowed to undertake work on their caravan/motorhome installation, they are not exempted from ensuring such work is carried out to an acceptable standard as set out in relevant codes of practice. which are accepted by the HSE and other safety related issues which include the duty to test before and after work is carried out on a gas installation.

In practice it is very unlikely a DIYer will have either the required knowledge of how to fully test a gas system, or to have access to the equipment of the required standard of performance to be able to complete their duty of care, which rather renders the exemption in the GSIUR impractical and I know from having worked in the industry potentially very dangerous it can be having had to provide reports on a number of incidents where injuries were incurred and in one case it was near fatal.

Note the exemption in the GSIUR only applies to the "owner" of the vehicle, which means it does not apply to the owner's spouse or any other relative or friend of the owner.

The vehicle must not leased or rented or loaned out (even to family members) as that constitutes it being used as part of a business, and thus the exemption would not apply.

If the vehicle is in shared ownership, for example if its under a finance agreement, you don't own the caravan, and thus the exemption would not apply.

If the owner asks or contracts anyone else to undertake work on the gas system they must be lawfully qualified and have the required "tickets" on their registration to undertake the gas work.

If you do undertake work on the gas system by claiming the exemption, and you later sell the caravan and the new owner establishes there is a problem with the gas system , as you were the last person to work on the system you could held liable under criminal law for any losses or injuries or deaths stemming from that work. Under criminal law one of the options is custodial incarceration, and a criminal record.

For those reasons I maintain it is unwise for DIYers to undertake any gas appliance repair or installation work unless you are fully qualified and insured to do so. which is why I consider the specific exceptions in the GSIUR are now a pointless and dangerous clause.

 

[Dustydog]

Grubber
When was the caravan and fridge last serviced?

If within the last year there a few things you can do .

I hesitate to say more because the advice from the Prof is not to be taken lightly. It sounds like a clogged flue or partly blocked jet. A good clean out may be all that is required..But if you have never done it don’t start now. Get an AWS mobile caravan engineer to sort it

 

[Grubber 12]

Sorry to sound a doomster but we recently had a new caravanner on here who had fridge problems on gas and ended up having a fire. I would follow the advice from Prof John and get an authorised servic agent to sort it for you.

Thanks. Can you share the post regarding the fire?

 

[otherclive]

Thanks. Can you share the post regarding the fire?

Unfortunately the OP has withdrawn and deleted the posts and pictures as it was the basis of an insurance claim and possible dealer liability.

 

[Grubber 12]

Grubber
When was the caravan and fridge last serviced?

If within the last year there a few things you can do .

I hesitate to say more because the advice from the Prof is not to be taken lightly. It sounds like a clogged flue or partly blocked jet. A good clean out may be all that is required..But if you have never done it don’t start now. Get an AWS mobile caravan engineer to sort it

To be honest, I think you will find that caravan fridges do not get routinely serviced. At best they will be tested on gas, 240v, and, at a push 12v, during the caravan's annual service. Any faults can then be rectified by someone that it is competent/gas safe. So all this talk on this post about getting the fridge serviced I don't think is relevant. Repaired by someone competent, yes. Overhauled by someone competent , yes. But serviced, no. It is like saying you need to get the pistons serviced on your car engine; they simply don't get serviced. They either work, or they break and need fixing..

 

[Grubber 12]

I trust that this may help:

Download the PDF file from this link

The fridge is quite easy to work on if you remove it from its fixed location, not in itself a difficult job but time consuming.

I found that parts were in the 'rip-off' price category from a lot of the main parts suppliers.
I could not obtain gas heating element, 230v heating element or 12v heating element at realistic prices and was forced to be shafted for same.

Some parts can be found easily at realistic prices, e.g. universal thermocouple £10 delivered -as opposed to £50 odd plus delivery from many suppliers.

What the attached diagram describes as 'magnet insert' ( I knew it as something else but cannot remember right now - it allows the gas to continue to flow after the igniter button is released and was the main reason for my fridge not performing properly), I suggest you replace it if you are going through a fridge overhaul routine.

'Magnet Insert' from main suppliers will be in excess of £80 from most of the obvious parts suppliers, but the same component can be had for less than £10 delivered.

I purchased a gas detector and gas leak detector spray and proprietary gas pipework sealant(s) and a manometer etc.

Take careful note of the placement of all fittings and installation items (foam room sealers and fittings), a camera is your friend here, take plenty of picures from various angles.

Safety being your prime concern.

Thank you for your response. Which was of great value. I appreciate all the safety advice from all the other posters but it was all of little technical help. With the support of a friend (domestic gas safe engineer); we did some further fault diagnosis tonight. He is convinced the problem is the thermocouple. Consistently now, we press the igniter button and the other button and the fridge ignites.. Every time. The manual says you are supposed to hold the button in for 15 seconds, we do that but as soon as you let go of the button the flame extinguishes. You spoke of a magnet insert being faulty on your fridge. I was wondering if perhaps if that serves to bypass the thermocouple rather than the spark button.? Did yours ignite? Or ignite and not stay lit?

 

[ProfJohnL]

To be honest, I think you will find that caravan fridges do not get routinely serviced. At best they will be tested on gas, 240v, and, at a push 12v, during the caravan's annual service. Any faults can then be rectified by someone that it is competent/gas safe. So all this talk on this post about getting the fridge serviced I don't think is relevant. Repaired by someone competent, yes. Overhauled by someone competent , yes. But serviced, no. It is like saying you need to get the pistons serviced on your car engine; they simply don't get serviced. They either work, or they break and need fixing..

The servicing of any caravan gas appliance is not part of the caravans general service. The general service will only look at the gas tightness of the installation, and the apparent correct operation (i.e. will it light up), so broadly your summary is correct. There is an adage if its not broken don't interfere, and much of the time that approach can work, it certainly prevents unnecessary interference with products and saves money.

However the environment in a caravan during storage is quite aggressive and and corrosion is usually active, the small crevice's are attractive to insects and spiders. These conditions can cause products to fail., and that seems to be a possible scenario for your own caravan.

Sometime it is necessary to strip gas appliances down to clear corrosion or other debris. but they are a scheduled strip down they are fix as necessary action.

 

[ProfJohnL]

Thank you for your response. Which was of great value. I appreciate all the safety advice from all the other posters but it was all of little technical help. With the support of a friend (domestic gas safe engineer); we did some further fault diagnosis tonight. He is convinced the problem is the thermocouple. Consistently now, we press the igniter button and the other button and the fridge ignites.. Every time. The manual says you are supposed to hold the button in for 15 seconds, we do that but as soon as you let go of the button the flame extinguishes. You spoke of a magnet insert being faulty on your fridge. I was wondering if perhaps if that serves to bypass the thermocouple rather than the spark button.? Did yours ignite? Or ignite and not stay lit?

The added information certainly could relate to the flame failure detection system, which would give the symptoms you describe. It is rare for the magnetic hold open valve to fail, it's more commonly the flame pattern on the burner not directing the flame (due to a blockage ) onto the tip of the thermocouple.

The blockage could be in the gas pressure regulator, the burner injector, the venturi, or damage to the burner flame pattern. - all matters that your LPG gas fitter should know and know how to check.

 

[Dustydog]

To be honest, I think you will find that caravan fridges do not get routinely serviced. At best they will be tested on gas, 240v, and, at a push 12v, during the caravan's annual service. Any faults can then be rectified by someone that it is competent/gas safe. So all this talk on this post about getting the fridge serviced I don't think is relevant. Repaired by someone competent, yes. Overhauled by someone competent , yes. But serviced, no. It is like saying you need to get the pistons serviced on your car engine; they simply don't get serviced. They either work, or they break and need fixing..

Most AWS engineers will test the fridge on gas. If there is a reduced performance my chap will remove the flue and clean the burner. If that doesn’t work then he tells me I need another job card😥

 

[Martin_E]

Depending on the fridge model…..if it’s one with a mechanical three way selection switch (no LED’s) then when you light the fridge with gas selected and while holding the thermostat in try wiggling the fuel selector left and right (without leaving the he gas select setting). Reason being it can be down to a bad contact on the selection switch that stops the flame from holding, also a bad earth with stop the fridge holding flame

 

[Buckman]

To be honest, I think you will find that caravan fridges do not get routinely serviced. At best they will be tested on gas, 240v, and, at a push 12v, during the caravan's annual service.

You are correct. Although the service may cost between £200 and £400 annoyingly the service centre never service the gas appliances which is probably the most dangerous thing in a caravan. They only test them which makes you wonder why they call it a service and why you pay so much at a service. The only servicing that is done is the running gear and the rest is just tests like opening and closing locker doors etc.

 

[Grubber 12]

The servicing of any caravan gas appliance is not part of the caravans general service. The general service will only look at the gas tightness of the installation, and the apparent correct operation (i.e. will it light up), so broadly your summary is correct. There is an adage if its not broken don't interfere, and much of the time that approach can work, it certainly prevents unnecessary interference with products and saves money.

However the environment in a caravan during storage is quite aggressive and and corrosion is usually active, the small crevice's are attractive to insects and spiders. These conditions can cause products to fail., and that seems to be a possible scenario for your own caravan.

Sometime it is necessary to strip gas appliances down to clear corrosion or other debris. but they are a scheduled strip down they are fix as necessary action.

Thanks for the input. You are explaining that the fridge needed repair. I agree. Nothing to do with needing a service. Wi

 

[Grubber 12]

Does anyone know what the needle gauge indicates? Is it the temperature of the thermostat?

 

[Dustydog]

The indicator is a galvanometer which uses a sensor to detect heat and produce a small electric current which moves the needle.. Thus they prove the gas burner is flaming. The gauges frequently fail although there is nothing wrong with the fridge working on gas.

 

[Grubber 12]

Thanks, if the thermocouple has failed I assume there will be no current getting to the galvanometer.

 

[ProfJohnL]

Does anyone know what the needle gauge indicates? Is it the temperature of the thermostat?

Semantics.. A service may indicate a repair is necessary.

 

[Anseo]

Thank you for your response. Which was of great value. I appreciate all the safety advice from all the other posters but it was all of little technical help. With the support of a friend (domestic gas safe engineer); we did some further fault diagnosis tonight. He is convinced the problem is the thermocouple. Consistently now, we press the igniter button and the other button and the fridge ignites.. Every time. The manual says you are supposed to hold the button in for 15 seconds, we do that but as soon as you let go of the button the flame extinguishes. You spoke of a magnet insert being faulty on your fridge. I was wondering if perhaps if that serves to bypass the thermocouple rather than the spark button.? Did yours ignite? Or ignite and not stay lit?

Thank you for your response. Which was of great value. I appreciate all the safety advice from all the other posters but it was all of little technical help. With the support of a friend (domestic gas safe engineer); we did some further fault diagnosis tonight. He is convinced the problem is the thermocouple. Consistently now, we press the igniter button and the other button and the fridge ignites.. Every time. The manual says you are supposed to hold the button in for 15 seconds, we do that but as soon as you let go of the button the flame extinguishes. You spoke of a magnet insert being faulty on your fridge. I was wondering if perhaps if that serves to bypass the thermocouple rather than the spark button.? Did yours ignite? Or ignite and not stay lit?

May I reply in more than 1 part?

1. The 'magnet insert' doeas not bypass the thermocouple or the spark button.
The heat of the flame on the tip of the thermocouple induces a very low current that is sent to the 'magnet insert', this current activates the magnet and holds it in the open position allowing gas to pass, if the thermocouple was defective then no current would be produced and therefore the magnet would not be energised and the gas flow would be shut off.

2.
In my case the fridge would ignite but did not stay lit, however it did have other issues that did not help with easy and reliable function of the fridge, spark gas distance, dirt and dust and most likely the thermocouple was overdue for replacement, I did not bother reinstalling the old thermocouple to prove a point.
I can however say with certainty that the 'magnet device' was faulty.
The gas heating element was also faulty, so even if the burner continued to be lit the fridge would not cool down very well at all, as it turned out the 230v element and the 12v element were both non functional ('cream crackered').

I did consult with a few 'technicians', one of whom was the 'fridge expert' for a major caravan dealer somewhat close to where I reside, when I explained all the symptoms of my fridge malfunctions he categorically stated that given what I had told him "the only course of action was to purchase a new fridge"; the so called fridge expert was talking rubbish.

A new thermocouple, a new 'magnet insert' and new elements and a general cleaning etc. were all that was needed to return the fridge to full working order, it remains to be functioning properly to date.

3. Regarding the needle gauge device you mentione in your original post:
Sorry but I have only just read your response to me and not all of the other responses since your post was made, if this has already been clarified then my apologies to you and others who may have responded to this matter.

On my fridge the needle gauge is somewhat erratic, sometimes the needle only just moves into the green area and other times it moves further into the green area, I have not fully investigated this but I suspect (happy to be corrected) that the device is not particularly well made and that the background (the green\red area segment) simply moves sideways depending on what jolts the fridge has received whilst in transit.

I hope that this may be of some help to you and would really appreciate learning of your findings with your fridge malfunction.

All the best.

 

[Grubber 12]

Thanks to you all for the valuable feedback. I am really grateful for some fantastic contributions and great advice. The gas safe engineer replaced the thermocouple with a cheapy universal one and all appears to be fine now. If it plays up again I might have him replace the magnetic insert and also fit an OEM thermocouple. Thanks again.

 

[otherclive]

Thanks to you all for the valuable feedback. I am really grateful for some fantastic contributions and great advice. The gas safe engineer replaced the thermocouple with a cheapy universal one and all appears to be fine now. If it plays up again I might have him replace the magnetic insert and also fit an OEM thermocouple. Thanks again.

Glad you got it sorted.. who’s to say that the OEM thermocouple isn’t a cheapie retailed at a non cheapie price? 😱