Dometic AES fridge/freezer RM7655L

[Clive Beeza]

When running on gas fridge light (gas) will work fine most of the time
but will then for unknown reason flicker, and the burner and pilot flame have gone out
if I turn the power selector control to off position for a few seconds,
and then re-select gas, and puff the flame relights and all is well until the next time,
have changed the gas valve, the flame burner, and jet, plus the relay,
all to no avail
The concern is if we are out for the day in summer
and it knocks off all the food contents could be ruined
so I need to fix the issue permanently
Any funsters come across this type of fault

 

[Branston]

When running on gas fridge light (gas) will work fine most of the time
but will then for unknown reason flicker, and the burner and pilot flame have gone out
if I turn the power selector control to off position for a few seconds,
and then re-select gas, and puff the flame relights and all is well until the next time,
have changed the gas valve, the flame burner, and jet, plus the relay,
all to no avail
The concern is if we are out for the day in summer
and it knocks off all the food contents could be ruined
so I need to fix the issue permanently
Any funsters come across this type of fault

Have you swept the chimney flue?

 

[Sleeveless]

Sounds like it could possibly be excessive resistance in the thermocouple circuit to ground , this is a known Dometic issue on some models and there is a service bulletin issued . The action of turning the selector off & on slightly improves the contact surfaces temporarily . The current running in this circuit is extremely low, measured in mA , this current is generated solely by the thermocouple. If the current is insufficient the gas safety solenoid will drop out and the valve will close. This is also more likely to happen on the lower of the two flame settings.

 

[Clive Beeza]

Have you swept the chimney flue?

Yes flue is spotlessly clean

 

[Clive Beeza]

Sounds like it could possibly be excessive resistance in the thermocouple circuit to ground , this is a known Dometic issue on some models and there is a service bulletin issued . The action of turning the selector off & on slightly improves the contact surfaces temporarily . The current running in this circuit is extremely low, measured in mA , this current is generated solely by the thermocouple. If the current is insufficient the gas safety solenoid will drop out and the valve will close. This is also more likely to happen on the lower of the two flame settings.

how do I get hold of the service bulleting you mention

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[TheTwoOfUs]

I have exactly the same problem and have all the parts you mention replaced by a Dometic service engineer and it still persists. I would be interested in seeing a service bulletin for this as well.

 

[Sleeveless]

Apologies , so many versions of this fridge ! With AES, the troublesome MES switch is replaced by a burner control module and the gas valve (GV100) is controlled by that. Although the same high resistance rule applies to the thermocouple connections, both to ground and to the control unit , also check the gas valve to ground, connections circled red below. Worth checking that the gas valve is getting a steady 1.5 volts from the control unit though . For anyone without AES , the bulletin is Dometic, "Flame does not keep burning" Publication-No.: 599 5183-07 en/Service 2003.10.16 BO/KV, for AES models the text below from Dometic is relevant. The burner control device ignites the flame when gas mode is chosen and supervises the ignition(safety time for ignition approx. 30 sec.). The recognition of the burning flame and its supervising is carried out with an ionisation electrode within the gas burner (flame failure device). To ensure good ground contacts an additional cable is mounted on the burner chassis.The gas valve GV100 is controlled by the burner control device

 

[Jabstatt]

I had ongoing issues and changed every component in the fridge control system, modules, burner, gas valve, thermocouple etc.

One day in desperation I removed the plug from the control box and cleaned all the pins.
Magic!
Never another issue!

Tony

 

[Clive Beeza]

I had ongoing issues and changed every component in the fridge control system, modules, burner, gas valve, thermocouple etc.

One day in desperation I removed the plug from the control box and cleaned all the pins.
Magic!
Never another issue!

Tony

There is a development with my Dometic issue
I firstly discovered that when I got the burner to light up if I turned the control knob to a near maximum cold stting the ignition light would stat fashing and the flame went out
I got it lit up again and left the cold dial around the 25 minutes (clock face) position
and it stayed alight with no issues for several hours
I have today found the problem had got worse
whatever position I turn the cold setting knob to
the igniter ticks away for about 20 seconds and than the fridge panel light goes on to flicker
and after several attempts with various control knob positions
merrily clicks away until it stops and has not lit up once.
having changed already all the obvious culprits now thinking it may be the control panel circuit board
any one any other suggestions

 

[Sleeveless]

There is a development with my Dometic issue
I firstly discovered that when I got the burner to light up if I turned the control knob to a near maximum cold stting the ignition light would stat fashing and the flame went out
I got it lit up again and left the cold dial around the 25 minutes (clock face) position
and it stayed alight with no issues for several hours
I have today found the problem had got worse
whatever position I turn the cold setting knob to
the igniter ticks away for about 20 seconds and than the fridge panel light goes on to flicker
and after several attempts with various control knob positions
merrily clicks away until it stops and has not lit up once.
having changed already all the obvious culprits now thinking it may be the control panel circuit board
any one any other suggestions

Well as it's less intermittent now and control units are pricey, you could test that theory by monitoring the current from the thermocouple into the control unit, and at the same time , the output voltage ( approx 1.5V) to the gas valve. Also checking the thermistor values.

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[Clive Beeza]

Well as it's less intermittent now and control units are pricey, you could test that theory by monitoring the current from the thermocouple into the control unit, and at the same time , the output voltage ( approx 1.5V) to the gas valve. Also checking the thermistor values.

An update for you guys following the thread
I explained all the obvious culprits I have changed
gas solenoid valve, electrical relay, complete burner unit,
cleaned the contacts on the multi block connector
on the burner control unit.
I have just removed the new burner unit to check out the jet
and as I had the original burner unit in the "spares box"
I compared the electrodes more out of curiosity than suspicion
on comparison I could see that the spark electrode on the "new" unit
was not shaped with a down curve like the original
I tightly gripped the metal end of the spark electrode
and carefully avoided straining the ceramic surround
until the tip was sitting just in front of the burner jet
and approx 4mm above the burner
put all back together switched onto gas and
literally after only one "click" the flame was alight
it has been running now for 2 hours
will keep fingers crossed that all is resolved and hope it helps others.
this burner unit was brand new and ready assembled,
who would have checked the electrode settings
certainly I didn't

 

[Sleeveless]

An update for you guys following the thread
I explained all the obvious culprits I have changed
gas solenoid valve, electrical relay, complete burner unit,
cleaned the contacts on the multi block connector
on the burner control unit.
I have just removed the new burner unit to check out the jet
and as I had the original burner unit in the "spares box"
I compared the electrodes more out of curiosity than suspicion
on comparison I could see that the spark electrode on the "new" unit
was not shaped with a down curve like the original
I tightly gripped the metal end of the spark electrode
and carefully avoided straining the ceramic surround
until the tip was sitting just in front of the burner jet
and approx 4mm above the burner
put all back together switched onto gas and
literally after only one "click" the flame was alight
it has been running now for 2 hours
will keep fingers crossed that all is resolved and hope it helps others.
this burner unit was brand new and ready assembled,
who would have checked the electrode settings
certainly I didn't

 

[Clive Beeza]

I have exactly the same problem and have all the parts you mention replaced by a Dometic service engineer and it still persists. I would be interested in seeing a service bulletin for this as well.

I have exactly the same problem and have all the parts you mention replaced by a Dometic service engineer and it still persists. I would be interested in seeing a service bulletin for this as well.

Hi Thetwoofus.
Just found a service manual download
google "Dometic RM7655L fridge/freezer service manual"
and hey presto
you have "Service -instruction from Gaslow
and they are all in the listing

 

[TheTwoOfUs]

Sorry, I didn't say that our fridge is the RM8555 model. Is there a service sheet for that model do you know?

 

[Clive Beeza]

Sorry, I didn't say that our fridge is the RM8555 model. Is there a service sheet for that model do you know?

Yes RM8555 is listed
just google the 8 series instead of the 7 series

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[a900ss]

Reading with interest. I have an RMT7655L with similar issues.

Is this a new service bulletin? Dometic in Tewkesbury replaced my burner about 2 months ago.

Replaced the burner, gas valve and burner control unit and still have intermittent issues where it just won't fire up on gas.

It’ll normally start fine (when I say fine, I mean after 8 to 10 clicks then whoosh, it’s alight) but after a few hours, it will 'tick,tick,tick' as it tries to relight but doesn’t and then I get the flashing orange LED.

 

[a900ss]

An update for you guys following the thread
I explained all the obvious culprits I have changed
gas solenoid valve, electrical relay, complete burner unit,
cleaned the contacts on the multi block connector
on the burner control unit.
I have just removed the new burner unit to check out the jet
and as I had the original burner unit in the "spares box"
I compared the electrodes more out of curiosity than suspicion
on comparison I could see that the spark electrode on the "new" unit
was not shaped with a down curve like the original
I tightly gripped the metal end of the spark electrode
and carefully avoided straining the ceramic surround
until the tip was sitting just in front of the burner jet
and approx 4mm above the burner
put all back together switched onto gas and
literally after only one "click" the flame was alight
it has been running now for 2 hours
will keep fingers crossed that all is resolved and hope it helps others.
this burner unit was brand new and ready assembled,
who would have checked the electrode settings
certainly I didn't

Before you made the adjustment, did it usually take longer than one click to light when it did fire up. Mine takes about 8 clicks but it’s still got issues.

It normally will ignite first time round but relighting is where I get an issue.

 

[Clive Beeza]

Before you made the adjustment, did it usually take longer than one click to light when it did fire up. Mine takes about 8 clicks but it’s still got issues.

It normally will ignite first time round but relighting is where I get an issue.

When I compared the old and new burner units electrodes
the new unit, when I now think about it, was very likely
sparking against the outer body of the holder,
and not near enough to the burner jet to fire up the gas,
re-setting the metal centre of the spark electrode,
being careful not to put stress on the ceramic encasement,
was what changed the start up firing to one click, and instant gas flame
hope this helps you

 

[Clive Beeza]

Reading with interest. I have an RMT7655L with similar issues.

Is this a new service bulletin? Dometic in Tewkesbury replaced my burner about 2 months ago.

Replaced the burner, gas valve and burner control unit and still have intermittent issues where it just won't fire up on gas.

It’ll normally start fine (when I say fine, I mean after 8 to 10 clicks then whoosh, it’s alight) but after a few hours, it will 'tick,tick,tick' as it tries to relight but doesn’t and then I get the flashing orange LED.

HI a900ss ( is that a Ducati by any chance )
what you describe are identical to the issue I was having
did exactly what you did changing all the gas line involve items
although I also changed the electrical relay which you do not mention
although my burner was brand new it turns out to be poorly
put together, as explained the electrode probe was not properly formed
only became noticed when I dropped down the burner assembly from the flue
(with gas pipe still connected) and set the spark going and saw it was
nowhere near the gas burner jet, hence the spark was not close enough to ignite the gas
check it out

 

[a900ss]

When I compared the old and new burner units electrodes
the new unit, when I now think about it, was very likely
sparking against the outer body of the holder,
and not near enough to the burner jet to fire up the gas,
re-setting the metal centre of the spark electrode,
being careful not to put stress on the ceramic encasement,
was what changed the start up firing to one click, and instant gas flame
hope this helps you

Brilliant.

And as a person very aware to not tamper with the gas, can the burner (also new from Dometic) be removed and adjusted without interfering with any gas pipes?

Thanks.

PS - sure is (was) a Ducati. Miss it but age comes to us all.

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