Dometic 8551 fridge not working on gas

[Mr Plodd]

The fact you cannot hear the auto igniter trying to light the gas, and you don’t get any light in the Gas symbol  tends to suggest that possibly the PCB in the fridge has died. If that IS the problem start saving! See here for a new PCB

[pfr]

With some fridge models you can clear a gas locked out fault. Not sure it will work on your model. It is common fault with auto fridge. 

Disconnect from ehu and switch off 12v power at the PSU for at least 1 min. Switch 12v back on at PSU but not the mains electric. Hold in the fridge power on button for longer period of more than 2 secs and see if this works. May not but worth a try.

Frank

Edited April 11, 2021 by pfr

[Mr Plodd]

Switching the main 12v control switch off doesn’t kill the 12v supply to the fridge because it will still operate on gas even with the master switch off!

 

You need  to go the back of the fridge via the lower external vent and disconnect the multipin electrical plug that feeds the fridge for a few seconds, then reconnect it.. That can have the same effect as “Ctrl/Alt/Delete” does on a computer (i.e. a reboot of the PCB)

 

That little trick has worked a couple of times for me in the past when my fridge played up. Certainly worth a try! 

 

 

[mark-w]

Many thanks for the top tips. Will give them a try tomorrow when I can back to the van.

 

Of the 2 mobile service chaps I've mailed. 1 has responded, but is now taking bookings for services in late Sept, early October.

Lets hope I don't have to wait that long

[mark-w]

23 minutes ago, Mr Plodd said:

The fact you cannot hear the auto igniter trying to light the gas, and you don’t get any light in the Gas symbol  tends to suggest that possibly the PCB in the fridge has died. If that IS the problem start saving! See here for a new PCB

Already looked into the cost of a new PCB, and to be fair, it was cheaper than I first thought. But still a fair chunk of change.

Will try a service and see if that helps throw any light onto my issue

[chinster1957]

16 hours ago, Mr Plodd said:

Switching the main 12v control switch off doesn’t kill the 12v supply to the fridge because it will still operate on gas even with the master switch off!

On Swift caravans the main control switch kills all 12v supply with the exception of the alarm system and solar controller.

[Mr Plodd]

6 hours ago, chinster1957 said:

On Swift caravans the main control switch kills all 12v supply with the exception of the alarm system and solar controller.

 

Really?? 

 

Most caravans are set up so the owners can turn off the main 12 v master switch if going out for the day (no supply to water pump, radio, lights etc) but there is still a 12v supply to the fridge for it to work off gas! That has been the case in all my caravans and motorhomes. 

 

Turn your master switch off and open the fridge door, I bet the light comes on! 

Edited April 12, 2021 by Mr Plodd

[Legal Eagle]

1 hour ago, Mr Plodd said:

 

Really?? 

 

Most caravans are set up so the owners can turn off the main 12 v master switch if going out for the day (no supply to water pump, radio, lights etc) but there is still a 12v supply to the fridge for it to work off gas! That has been the case in all my caravans and motorhomes. 

 

Turn your master switch off and open the fridge door, I bet the light comes on! 

Not in my Swift it doesn't. If I power down the main PSU it isolates 12v to everything except the toilet flush pump. However, if I switch off the control panel above the door it only isolates the water pump etc. When we go out for the day we just switch off the control panel above the door. I'd have to get on my hands and knees to access the PSU master switch under the front seat everytime otherwise.

Are you sure you aren't confusing the control panel isolation function and main PSU shutdown?

Edited April 12, 2021 by Legal Eagle

[Mr Plodd]

I have never switched off at the PSU, I always use the control panel switch as I have always understood that’s what it’s for, to switch everything except the fridge  (and alarm of course) off. That way the caravan can be left with only the fridge receiving 12volts, hence the instructions in my handbook (Bailey)  which say to be sure to switch the fridge itself off at the fridge when laying  the caravan up or it will flatten the leisure battery. 

 

Dont think I have ever heard of anyone else switching their 12 v off at the PSU (until now)  I didn’t even know it was possible!! 

Edited April 12, 2021 by Mr Plodd

[Legal Eagle]

I cannot speak for other manufacturers as I have only owned Swift Group brand caravans (Abbey, Sterling & Swift). The Sargent PSUs in Swift and, I believe possibly Coachman, caravans have a full 12v system shutdown button for when the caravan is not in use for a protracted period e.g. storage. By isolating 12v power it helps prevent leisure battery drain.

The control panel above the door is not a master switch but controls 12v power to the water pump and lighting etc. but not the fridge or heating etc. and that is what is switched off when going put for a day.

All of that is explained in the handbooks.

Edited April 12, 2021 by Legal Eagle

[Mr Plodd]

Having never owned a Swift group caravan I accept what you say. However I have owned several motorhomes all of which were fitted with Sargent systems and in them there was no specific 12v isolation switch other than the control panel master switch!

[mark-w]

Well I delved into youtube yesterday to try and see if there was a solution.

Several videos had different ways of changing to gas. 1 video had you press the gas button once to tell the system to prepare for change, (as the bloke said) and then again to change over.

Another video just had it on 1 button change.

But they all had one thing in common, when buttons are depressed there is a beep. 

Ours doesn't beep but it does beep when 240v is chosen and the 240v is disconnected.

But I'll visit later and play around with the pilot light, well have a look around it to check for cobwebs. And I'll take a spirit level to ensure it is perfectly level

Edited April 13, 2021 by mark-w

[Mr Plodd]

Lack of any beeping does  tend to suggest it’s an issue with the PCB. But try physically disconnecting the 12v power to it for 30 seconds, that might just “reboot” it.  These fridges don’t need to be that level so don’t bother with the spirit level, that’s not going to influence  the lack of beep! Even if hopelessly out of level it should still light on gas, it just won’t cool down. 

Edited April 13, 2021 by Mr Plodd

[mark-w]

3 hours ago, Mr Plodd said:

Lack of any beeping does  tend to suggest it’s an issue with the PCB. But try physically disconnecting the 12v power to it for 30 seconds, that might just “reboot” it.  These fridges don’t need to be that level so don’t bother with the spirit level, that’s not going to influence  the lack of beep! Even if hopelessly out of level it should still light on gas, it just won’t cool down. 

 

 

Thanks. Will try your suggestion.

Going away on Friday for the weekend, so will have to use the back up plan. We have a 50l Waeco fridge we used when we went touring Europe/Africa with our LandRover. So that will be dragged out of storage.

Managed to get a service booked. But not until May 14th.

[Mr Plodd]

You could always run the caravan fridge off EHU and save your (very expensive) gas ! I can’t remember the last time my fridge was on gas! (But I do check it every few months to ensure it will  light up!) 

[mark-w]

Just now, Mr Plodd said:

You could always run the caravan fridge off EHU and save your (very expensive) gas ! I can’t remember the last time my fridge was on gas! (But I do check it every few months to ensure it will  light up!) 

There in lies the issue. We're going away this weekend and to try and have a peaceful weekend we try and go to sites with no kids. Which invariably means no facilities or EHU.

Hence the mad panic to sort the gas out

[Mr Plodd]

Ah!! I now understand. Waeco on gas it is then! 

[mark-w]

11 minutes ago, Mr Plodd said:

Ah!! I now understand. Waeco on gas it is then! 

Waeco will be run from the LR Defender which is setup for expeds. So not as comfortable as the wifes Evoque. But then it's just a drive to the New Forest and back. Not as though were going to be visiting to many places

[mark-w]

Plot thickens.. if I disconnect the power plug in the side compartment I can get it to light on gas. As soon as I reconnect the plug the pilot goes out. 
inside the gas lit light on the control panel flashes every  8 secs or so. But the temp reading indicators are not lit

 

How long before I should feel coldness in the fridge? Either the air or the cooling fins?

Edited April 14, 2021 by mark-w

[Mr Plodd]

That is very odd isn’t it? 

 

The fins on the back of the fridge get (very)  hot not cold you should feel that after 15-20 minutes. 

 

[mark-w]

4 minutes ago, Mr Plodd said:

That is very odd isn’t it? 

 

The fins on the back of the fridge get (very)  hot not cold you should feel that after 15-20 minutes. 

 

Completely bonkers. I use my watch to check the temperature inside the fridge so not very scientific.

temp drops from 18+ on my arm down to 6deg after an hour or so. .

 

so going to leave it on gas overnight and as I’m in Birmingham tomorrow so the  Mrs will check the fridge . If it’s cold, she’ll try and out it over to mains to get it down and keep it cold until we leave on Friday 

[Martin]

3 hours ago, mark-w said:

Plot thickens.. if I disconnect the power plug in the side compartment I can get it to light on gas. As soon as I reconnect the plug the pilot goes out. 

FYI those 4 wires on that connector are 12v +/- for the electric element (to cool when towing) and also the fridge control 12v feed (+/-).

 

When it worked on gas (with that plug out) was it also on 240v?

 

Its odd that it works as the instructions state : For MES and AES it is compulsory to provide a permanent 12V DC supply at the terminals C/D (permanent voltage supply for functional electronics).

[mark-w]

2 minutes ago, MartinJB said:

FYI those 4 wires on that connector are 12v +/- for the electric element (to cool when towing) and also the fridge control 12v feed (+/-).

 

When it worked on gas (with that plug out) was it also on 240v?

 

Its odd that it works as the instructions state : For MES and AES it is compulsory to provide a permanent 12V DC supply at the terminals C/D (permanent voltage supply for functional electronics).

It 240v supply was turned off so no mains power going in.

I do have the batteries fitted in  the rear of the control panel. So that’s  where  it’s getting it’s 12v power from. 
off to check it in a bit. Hopefully it’ll be proper cold.

[Martin]

Ah yes I forgot the batteries so you did fit some, that sure does explains it and is a design intention so should be quite safe - something funky is going on there! Might be worth checking the 12v element feed is dead.

[Mutley]

On 11/04/2021 at 11:06, mark-w said:

We purchased our can last year in between lockdowns. Hopefully going away next weekend so pulled it out of storage for a clean and going over.

fridge works on 240v but not gas or 12v.

when I say it won’t work, I can’t get it change over to 12v or gas.

ive checked the battery’s behind the control panel, 6X  AA batteries but they are missing.

is this the reason why it won’t work?

I have it connected to the mains 240v so would of thought it would step the power down to function on 12v and gas?

She you say you can’t change over to gas or 12v do you mean when you press the gas select button it doesn’t light up and same for 12v

 

if the symbol lights up and flashes along with the flashing triangle then for  the gas it has probably gone to gas lockout,  you should be able to press the flashing triangle for about 3 seconds, this will reset the gas fault, the 12v if you can select it but flashes will probably be due to no car with engine running attached to van.