Dometic Refrigerator Problem on Gas

[Hit Hard]

The Dometic refrigerator SP-219 in our 2019 Lance travel trailer 2465 works perfectly on electric but on gas it will start, then when it reaches temperature, it cycles off and the #3 and #7 lights start flashing, and it will not cycle back on.  I can turn it off, let it warm, turn it back on, and it does the same thing (and will not cycle back on).  I'm level, thermostat position is correct, flu is clean, batteries are in excellent condition, and all connections have been checked.  The problem persists whether on shore power or battery power.  The problem began intermittently a few months ago but in the past few weeks it has become the norm.  Any suggestions?

[oldjohnt]

45 minutes ago, Hit Hard said:

The Dometic refrigerator SP-219

Is that the correct model ??

John T

[Hit Hard]

Good catch, oldjohnt!  I had just realized myself that I'd put down the # for the control box.  The correct Dometic refrigerator model # is DMR702.

[Ray,IN]

Dometic DMR702 installation and operation manual.   pages 18 and 19 address not working on gas and error codes.

[Kirk W]

Quote

With symptoms of weird or erratic operation, and all other electronics test good, you will need to eliminate the possibility of RF interfering with the lower control board. To test, completely deaden the RV (unplug shore power and disconnect the batteries), bring an alternate 12VDC source to the back of the fridge and run the unit isolated. This will essentially bench test the fridge without the need to remove it from the RV. If the problem persists, replace the lower control board.

The above comes from the only service manual that I have been able to find for the 702. Here is a link to download a copy of this manual.   Dometic 702

[oldjohnt]

After performing troubleshooting in accordance with the manuals above ifffffffffff indeed the problem turns out to be the control board ?? I recommend a Dinosaur Electronics replacement if they manufacture one for your fridge.

http://www.dinosaurelectronics.com/

John T

[Kirk W]

Hit Hard, have you found any help here yet? Let us know what is happening and we might be able to give you more ideas. 

[oldjohnt]

Have you looked at these DMR702 error codes to see if it helps you find the problem??

https://www.arprv.com/rm3762-dmr702.php

John T

[Hit Hard]

I really appreciate the interest and the input from all of you guys!  I am definitely going to make notes about the dinosaur electronics site AND I'll be printing out the info on the error codes as well.  These sources are much more detailed than any of the info I've been able to find.  In the meantime, I tested the RF interference issue per Kirk's instructions and it has now cycled off and back on with NO PROBLEM!    SO, I assume I don't need to replace the control board, but how do I clean up the RF interference???  We do put a lot of miles on the camper, but when it is home, it stays in a building powered from my workshop that has numerous welders, machine shop equipment, etc.  Could any of that be the culprit?  The problem has only manifested in the last few months but we've owned the camper for about 1.5 years.  I've read that solar panels might cause RF problems and the camper does have one on it, so...?  BTW, we're leaving out a week from tomorrow for a couple of weeks as I'll be teaching blacksmithing in Nebraska (retirement hobby!).  Thanks again for all your help.

[Kirk W]

12 hours ago, Hit Hard said:

I assume I don't need to replace the control board, but how do I clean up the RF interference???

RF is a difficult problem and an arc welder could be the culprit if you are experiencing the problem near one that is in use. Your welder or any other equipment could only be the cause if you are experiencing the problem when using the refrigerator near them but the problems would not follow you when you travel. An RF problem normally takes place when you are near the source or if the source is inside of your RV. It isn't impossible that your solar equipment is causing it, but it is unlikely as I have never heard of that reported. An RF source that could follow you would be a florescent light as those are a fairly common source of it. It would only happen with the light on. I once had one in our RV that would mess up the TV reception only on certain channels.

Some type of shielding that is well grounded might help but removal of the source is a better correction. The advantage to shielding is that finding the source can be difficult. Since this seems to be an intermittent problem, you need to determine what is different when the problem happens, versus when it does not. 

Keep us posted as this is an issue that I have dealt with, although not with a refrigerator. Like most field technicians, I did run into it from time to time and usually it was not easy. 

Edited September 28, 2020 by Kirk W
Add a little more.

[oldjohnt]

Hit Hard, thanks for the update, you ask: 

11 hours ago, Hit Hard said:

how do I clean up the RF interference???

That's above my pay grade, but when I "Binged" it I came up with this which is way too much for me to absorb, take a look:

https://www.bing.com/search?q=reducing+rf+interference&cvid=4db1a9b872b54ab89d27783170d6ade4&FORM=ANAB01&PC=LCTS

While its possible for certain equipment in your shop, if operating and especially starting and stopping, to emit RFI that could in theory affect your fridges electronic circuit board subject to proximity and other factors, in 49 years of RV ownership (including being a used dealer) and having shops with welders or compressors or HID or fluorescent lighting , I NEVER experienced the problem you described, but that's NOT to say its impossible.. 

 If you continue to troubleshoot by powering the fridge with an alternate source and by experimenting with operating shop equipment such as lights and welders and compressors etc maybe you can isolate RFI as the cause ???? but I wouldn't bet too much on that...

If not go back to the basics and analyze any error codes (see above links and manuals) and I would one more time check all connections, grounds and voltage levels. I have cured problems in fridges or water heaters or furnaces by removing and cleaning circuit board contacts and re attaching.

Just how close (or is it inside) is the RV to your shop and what is operating (HID or fluorescent lights, welders, air compressors, motors) when the problem occurs???

Best wishes, let us know your results     

John T 

[Hit Hard]

John T,

 

[Hit Hard]

17 hours ago, Hit Hard said:

John T, thanks again for your input.  Before I did the bench test, I killed all power to the camper including the onboard batteries and let it sit a while, did the first test, and it still failed.  Then I hooked the refrigerator directly to an auxiliary battery as you recommended and that solved the problem.  Since then, it has worked fine hooked either to the camper batteries or to the shore power. 

In answer to your question, the camper is stored in a metal building about 50 feet from the shop and the problem happened even when nothing was on in the shop.

I will clean the ground wires at the refrigerator as a preventive, and if it fails again I will go through all of your recommended steps.  I do agree with you that it's best to stay with the basics, so analyzing error codes and checking connections would be first (and I will read up on RF interference as per the search you suggested).

Best of luck and thanks for your knowledge!

Hit Hard

 

17 hours ago, Hit Hard said:

 

 

 

[Hit Hard]

Kirk, I just reread the posts and your info on shielding, etc. is interesting.  Since the problem WAS intermittent and I can’t think of anything that could be related to it, I’m hoping the problem is now resolved (of course I’m not holding my breath!). 

The really strange thing about this is that we have a friend who purchased the exact same camper and the same time we purchased ours and they are not having the problem.

I do miss the time when you could look at something and see points burned up, etc. to fix a problem, as opposed to looking at a circuit board and scratching your head.  I guess the benefits of modern electronics just have to come with some down sides.

Fortunately, we rarely need to run the refrigerator on gas.  We do use it to cool it down quickly, but then we usually operate on electricity.  Used to leave gas on while traveling but then read what a hazard that could be if there were an accident so stopped doing that – can well imagine that insurance wouldn’t pay if the worst happened and the gas was found to have been left on!

Thank you for your help, and thank you for your service to our country as well.

Hit Hard

[Kirk W]

2 hours ago, Hit Hard said:

Used to leave gas on while traveling but then read what a hazard that could be if there were an accident so stopped doing that – can well imagine that insurance wouldn’t pay if the worst happened and the gas was found to have been left on!

RVis designed to be in use while traveling and there is a "stop flow" valve that closes if there is a line rupture but there is a small risk from traveling with it on. Many of us do so and have done so for years and there is no problem with insurance if that should happen. I know that some claim to know of cases where the propane in use has ignited in an accident but in a seminar at a Good Sam rally there was an insurance investigator who stated that there are no documented cases of it. There also have never been a claim denied for that reason. He stated that the most dangerous thing to travel with is a tank half full of gasoline. 

[oldjohnt]

8 hours ago, Hit Hard said:

John T, thanks again for your input.  Before I did the bench test, I killed all power to the camper including the onboard batteries and let it sit a while, did the first test, and it still failed.  Then I hooked the refrigerator directly to an auxiliary battery as you recommended and that solved the problem.  Since then, it has worked fine hooked either to the camper batteries or to the shore power. 

In answer to your question, the camper is stored in a metal building about 50 feet from the shop and the problem happened even when nothing was on in the shop.

I will clean the ground wires at the refrigerator as a preventive, and if it fails again I will go through all of your recommended steps.  I do agree with you that it's best to stay with the basics, so analyzing error codes and checking connections would be first (and I will read up on RF interference as per the search you suggested).

Best of luck and thanks for your knowledge!

Hit Hard, You're welcome, thanks for the detailed feedback. The fact that alls well AFTER you disconnected and hooked to an auxiliary battery then back to the RV battery really makes me suspect either a connection,,,,,,,,,, or ground,,,,,,,,,, or a voltage problem,,,,,,,,,,, or the DC power system (Batteries and Charger etc) in the RV, but hey as is said "If its not broke (now) don't fix it" lol.

The fact the RV is in a metal building 50 feet from the shop and the problem occurred even when nothing was on in the shop, makes it even harder to believe any sort of RFI was the cause of your problem as posted above.  Like I said in 49 years or RV ownership and sales in proximity (within same shop even) to all sort of welders and compressors and HID or Florescent lighting I NEVER experienced any RFI related failures.

 With  my abundance of Solar and Batteries and Inverters I have ran my fridge on 120 VAC when driving but usually I operate on LP Gas.

Best wishes, God Bless, safe travels, fun working with you

John T

Edited September 29, 2020 by oldjohnt

[Ray,IN]

John is it possible the complete disconnection reset the control board and self-corrected the problem?

I like the KISS principle.

Edited September 29, 2020 by Ray,IN

[oldjohnt]

47 minutes ago, Ray,IN said:

John is it possible the complete disconnection reset the control board and self-corrected the problem?

Hey good neighbor, I would say that's "possible" there are certain electronic components or devices out there which a simple power down and re set may cure, I just cant say if his control boards is one of them?? However a voltage or connection or  ground or DC supply issue is also a possibility, hard to say from here..I'm headed out again soon are you ???

John T

[Wrknrvr]

    This is subject you may want to study. And I only copied this so it wood point you in educational direction.

https://www.caplinq.com/blog/copper-foil-tape-for-emi-shielding_2652/

 

  I stumbled into copper tape for another subject. 

 

 

   Vern in a T-shirt 

[Kirk W]

14 hours ago, Ray,IN said:

John is it possible the complete disconnection reset the control board and self-corrected the problem?

I'm not John but I have worked with the RF interference issue in my career and while anything is possible, it is very unlikely, especially since the problem being intermittent seems to indicate that it only happens when the RF source is in operation. Clearly it won't harm anything to disconnect everything just to find out and see if that helps. That type of fix is much more likely with microprocessor controlled circuit boards and none of the refrigerator boards that I have looked at have the feature, but that doesn't mean they don't exist. The most common way that RF interferes with equipment is when some part of the circuit is acting as an antenna and that is usually a function of the RF frequency and the wave length. I have seen things as simple as making the power cord shorter, resolve that type of issue. Back when I first learned basic electricity, power was power and it was either there or it was not but with the move to solid state devices and microprocessor circuits, "dirty" power has become a growing problem. Some expensive equipment today often has power filtering built into it just to prevent this sort of problem.

55 minutes ago, Wrknrvr said:

This is subject you may want to study.

That is an interesting idea. When you start to add shielding the key is to be careful to make sure that it doesn't get into the wrong place and short something out as the best shielding is also an excellent conductor. 

[Wrknrvr]

  Just out of curiosity, do you always have your 12vdc battery connected. And is it working properly.

  As that can pass some low voltage AC power though the 12vdc system.

 

  Vern in a T-shirt 

[Kirk W]

1 minute ago, Wrknrvr said:

As that can pass some low voltage AC power though the 12vdc system.

A very good point, as all of the controls are powered by 12V-dc and that would be the most probable antenna. Since the only thing that 120V-ac power does is to supply the heater that replaces propane in the electric mode, you can just unplug it. 

[oldjohnt]

1 hour ago, Wrknrvr said:

Just out of curiosity, do you always have your 12vdc battery connected. And is it working properly.

  As that can pass some low voltage AC power though the 12vdc system.

Hey Wrknrvr, Indeed what AC gets through the rectified 12 Volt DC supply system (which powers the fridge 12 Volt electronic circuit board) depends on the quality and filtering capacity of the Converter/Charger when plugged to shore power. A good quality charger likely has less ripple and improved filtering versus a cheaper unit. Poor quality DC (along with any unwanted AC) getting into his system may be a cause (if its circuit board related) of his problem as well as RFI from a shop located 50 feet away with nothing running which I tend to doubt, even though sure possible. NEVER SAY NEVER !!!!!!!!!!!!!

Of course, if he is hooked to an independent battery NOT connected to his RV charger and the problem goes away but re occurs if connected to shore power, then the quality of the AC source,,,,,,,,,, or his Converter/Charger,,,,,,,,,,, or RFI comes more into suspicion. Even if the fridge were running on AC, the 12 volt DC powered electronic  control board is still subject to the 12 VDC quality while on LP Gas it is likewise.

Not being there we cant diagnose his problem over the net, but a faulty circuit control board,,,,,,,,,,, or a faulty Converter/Charger,,,,,,,,,,,,, or an AC power problem,,,,,,,,,,,,,,,,,,, or yes even RFI which I doubt, OR IT MAY HAVE ONLY BEEN A CONNECTION OR GROUND OR LOW VOLTAGE PROBLEM

Darn if I know sitting here lol

Its fun and a pleasure sparky chatting with all you gentlemen, thanks and God Bless

John T Longggggggggg retired but ever curious Electrical Engineer

[Kirk W]

1 hour ago, oldjohnt said:

Even if the fridge were running on AC, the 12 volt DC powered electronic  control board is still subject to the 12 VDC quality while on LP Gas it is likewise.

As I said before, the problem is probably not bad 12V power but rather the antenna effect of the supply leads. When that happens, it really doesn't matter what the source does. I have dealt with the problem before, although not with an RV refrigerator. 

[oldjohnt]

1 hour ago, Kirk W said:

I have dealt with the problem before, although not with an RV refrigerator. 

Same here Kirk, Ive experienced RFI, but like you NEVER with an RV refrigerator and I've had them in the same building close to welders, compressors, HDI and fluorescent lighting...........

Take care now fun chatting 

John T