Dometic fridge on propane-Yellow light flashing but still coolng-kinda

Hi there
Wanting to see if camping is for us with minimal investment, we bought an 07 Nomad 150 LTD.  Hope to take it around Lake Superior this September to get our feet wet, but have a few bugs to work out first.

The fridge is a Dometic RM 7401.  Can't seem to find any information on the particular problem that I am having.  It will start no problem on propane, even cools down.  However, the yellow light never stopped flashing (even after cycling it on and off like the manual says).  After an hour or so,  the flame went out and reignite several times.  After a few times cycling, it did not relight.  I let it sit a little while and it started again when I cycle the selector switch.  After a while, it did the same thing...

When we looked at the trailer, I had a friend who knows a little bit about campers come with me to help check it over, but we didn't let the fridge run long enough for it to quit and he was thinking the yellow light flashing needed to be addressed, but wasn't a deal breaker.  He also commented that the pilot flame on the water heater looked a little weak if you think that is some how related   

Thanks
Steve   

Is the yellow light you're talking about flashing every time the igniter triggers? Probably just needs all the rust and crud blown out of burner. Good flame will be blue and steady.

jubileee said:

Is the yellow light you're talking about flashing every time the igniter triggers? Probably just needs all the rust and crud blown out of burner. Good flame will be blue and steady.

Click to expand...

To add to what Jubillee said I recall a similar problem on my previous RV and ended up paying a repair shop an hour's labor to simply blow out the hollow tubing that  fed air to the burinng flame.  It seems that spiders like to build nest in that tubing for whatever reasons spiders have of doing such things.  You can figure out which metal tubing that I am referring to when you take off the access panel on the outside behind the refrigerator.  Hoping it as easy as this to fix your issue and get a stronger flame.  Look at part number 108 here.

http://www.laurelhurstdistributors.com/parts/refrigerators/dometic/RM7401.html

You never said if it worked on electric, but I am assuming that it does.  If it doesn't, then perhaps you might have a more serious problem with crystal formation in the ammonia coolant.

Is that flashing yellow light labeled "Gas"?  That's the only flashing yellow I could identify for the 7xxx series Dometics. Supposedly it indicates a gas lighting fault, e.g. no propane or failed ignition. But you say it cools ok...

Also, is there another light labeled "230v" or "Mains". Everything I can find on the RM 7401 indicates that its electric operation is designed for European standard electric power (230v) rather than US. If so, then it won't ever enter electric mode in the USA or Canada. Seems like an odd choice of fridge for a US or Canadian camper.

Thanks for the replies!

Jubillee
This problem does seem a little different than other ones I have read about because the yellow light NEVER stops flashing, even with it lit and cooling.  You can hear the igniter quit once the fridge is lit.

Joulp
Nice link and part #.  Makes it real easy.  I will probably take that out, have a look at it and clean it while I am at it.  I did have it running on 110 and Battery, but not very long.

Gary
Yes, flashing on gas.  In my manual it says it runs on Gas, 12V DC, and 120V AC.  Though it does list 230V in place of 120V in the trouble shooting guide....... The manual does imply a lighting fault.  But it lights fine, just doesn't stay running as stated above.  Also, under section 5.2.4, (Gas faults) it does say that "If after 30 seconds the operating display starts flashing red again, the gas fault has not cleared.  (E.G. air the gas line)"  Not sure if red is a typo, but I have only seen yellow and it has never stopped flashing (cleared?).  I have cycled the switch several times with no success. 

So, one thing I am wondering is if there is a pressure issue in the system that is bad enough to register a fault, but not bad enough to shut it down until it warms up for some reason?

My plan for now is to take part #108 out. inspect it and clean it up.  Hopefully that will take care of it. 

Thanks
Steve



 

Since the AC power only operates the heater element, a 230v heater will work on 120v power. It merely does not produce as much heat to drive the cooling unit (about half).  And it's quite possible that a 120v heater was substituted on yours - it is a simple, plug compatible swap.  I doubt if the fridge circuit board has a way to measure gas pressure. Most of them only detect whether the flame lit or not (flame sensor), but they also shut off the gas valve if no flame is detected. If you have cooling and the flame under the boiler is lit, obviously the gas valve is open and working.

I can't find a service manual specific to this model-series and similar Dometic AES models do not have the yellow light, flashing or otherwise.

There is a feature on many Dometics that is called "back-up mode" or "standby operation" or similar words. It activates when the circuit board detects an internal failure in temperature control and runs the cooling unit non-stop. I wonder if a flashing yellow might mean it is in that back-up/standby mode, whereas red would mean no cooling at all. The typical reason for the back-up operation mode is a failed temperature sensor (thermocouple or thermister) inside the fridge, or a broken wire to it. The thermocouple is usually clipped to one of the cooling fins inside the fridge.

Stevecamper said:

Hi there
Hope to take it around Lake Superior this September to get our feet wet, but have a few bugs to work out first. 

Click to expand...

Why drive all the way around to get your feet wet. Just pull off the side of the road and walk in.  : ;D
I just had to. 

Welcome to a fun and informative forum.

An update

I took  the flame tube thingy (#108) out and cleaned it up.  There was some crud, but it didn't seem to be obstructing the flame any.  Also cleaned up all related wire connections too.  All this may have helped some.  Now, it pretty much stays running with though occasionally the flame will go out and immediately relight.  I pulled a couple of wires connected to the solenoid while it was running to see what they would do, and one of them makes the flame smaller when you pull it.  Assuming a pilot mode or something? and another shuts it down.   

Anyhow, I left it running and after a while the yellow light went solid!  It started blinking again after I opened the door to check the temp...  This has happened a few times, with it flashing most of the time.  Temp seems steady at about 42 degrees in the fridge section.  Currently I have it on AC and put a more legible thermometer (digital) in it.  I have the temp set most of the way clockwise and will adjust it the other way tonight to see of there is a temp swing at all.

A couple questions.
First, what could be causing the flame to go out occasionally-relighting immediately?  Flame appears solid. 
Second, any safety issues you can think of? 

Rene, Good one.  didn't catch that one!  :

Stevecamper said:

An update


...A couple questions.
First, what could be causing the flame to go out occasionally-relighting immediately?  Flame appears solid...

Click to expand...

Is it possible that your flow of propane is not steady, perhaps with air in the line.  When you run your cooktop is the flame steady?

Joel

Well, not really any further.  Mostly been monitoring the fridge while working on other things. 

I have had 2 burners on the stove going while the fridge is on.  The flame on the stove was steady.

The fridge's performance is the same on AC as it is on gas (except the indicator light is flashing on gas).  The temp in the fridge goes down to 39-40 at night, but up to 50 during the day with outside temps reaching 85-90.  It seems the gas is now only shutting off when the temp is down to 40.  When I opened and closed the door, it started again in a minute or so which I am guessing would be normal if the temp was set at 40?.  Thermostat doesn't seem to make a difference no matter where I set it though, and seems very loose, like perhaps it is broken, but seems to be attached to the controller properly. 

One other thing of note is during the day when the fridge should be working hardest, the counter over it is pretty warm, especially toward the back.  The back doesn't appear to be insulated well and probably isn't helping any. 

Anyway, I will pull the fridge out far enough to get at the controller to look at it, but I am getting worried that the fridge is just dying.  Can't really justify sinking to much into it. 

Any more thoughts?
Steve

Gary RV_Wizard said:

Since the AC power only operates the heater element, a 230v heater will work on 120v power. It merely does not produce as much heat to drive the cooling unit (about half). 

Click to expand...

Actually, a 240v heating element operating on 120v will not produce half as much heat.

P = V x I = V x V / R. Thus, it produces only 1/4 as much heat. That probably won't accomplish much.

Joel

Make sure the burner flame is touching the flame electrode.  This sets up a current flow that tells the circuit board that the flame is lit.

If the electrode is not in the flame (maybe the burner is partially blocked?) or if the electrode is covered in crud, this can interrupt the flame sensing current and make the circuit board think the flame has gone out.

Just a thought...How is your propane level and is the tank valve open all the way?

Update-looking up

The manual does say it runs on propane, 12v DC and 120v AC, so I am thinking that AC voltage isn't the issue.  Also, propane seems good.  Even with 2 stove burners running full tilt.

I was suspicious that the thermostat adjustment knob was broke, or not connected.  Ended up tearing the controller apart and found the nob on the end of the actual temperature adjustment unit thingy in the controller was broken.  I slotted it for a screwdriver just to see if that would solve at least the temperature issue.

I had to pull the fridge part way out to get at that, so I also looked into why the counter on top of the fridge would get as hot as it does.  Found that the rear of the fridge was not sealed from the heat or fumes as it should be (from the manual).  The Flu pipe does not run all the way to the grill either.  These issues can cause fumes to get into the camper as well as allow unwanted heat around the fridge, detracting from it's performance.  The manual says that if the fridge is sealed around the back, the flu pipe does not need to run all the way to the grill.  Pretty surprised to find it set up this way.  I sealed the fridge and extended the flu gas pipe to within an inch of the grill for now.     

Anyway, I now have a cold fridge (34 degrees currently) but won't see any hot ambient temps for a while to really test it.  Now that I know the fridge will actually make temp (and worth putting money into) I will get back to my original issue with the gas fault light.

I agree about the flame sensor electrode.  Sounds like yours may be what is cutting off your gas (thinking flame is not present), then relighting, at which point it runs a while until the bad or misaligned or dirty sensor tells it to turn off.

Well, it appears that the fridge is good to go.

Fixed the broken thermostat, also a loose wire connection, and sealed the back of the fridge.

Gas stays on with no flashing light, and the fridge easily cools into the mid thirties.  Also only gets up to lower 40s on a hot day.  Lots of labor figuring it out, but not much money so pretty happy.

Replace a couple of broken brackets on the awning, the shower head, a shelve under the sink in the bathroom too.  Now onto the fresh water tank....