Need help Dometic fridge

[Wnaplay]

At the campsite last weekend we had a park electrical issue affect about 15 spots. Turns out one of the legs or ground came off in the electrical panel at the park which resulted in everyone's power acting like it was only operating at half strength. When they finally got it figured out we realized our dometic fridge wasn't working. We had a blown 5A fuse on the control board. We replaced it and turned it back on. Set it to auto, no gas, after a few minutes the check light came on. After some testing we lost all power completely to the fridge, for what reason I have no idea, there was power just nothing functioned including the inside light. I get home and plug it into shore power, again nothing. Out of frustration I might have "tapped" the control board with the screwdriver handle and it all came back on again. I lit the fridge on gas to make sure that worked, then turned the gas off and let it run with the auto light on expecting the check light to come on again but it didn't so I thought maybe it's fixed. I let it sit for 24 hours and checked it, no check light but it didn't cool either. I unplugged the shore power and check light came on, I assume because I had the gas off and it was set to auto. Can anyone help figure this thing out. Any advice is greatly appreciated

[JohnB]

Hi Wnaply, Welcome!

This is going to get a little technical and we do not know how handy or comfortable you are with electrical things.

As a start, it would help if you can confirm the make, model and year of the fridge. (look inside the fridge compartment on the left or right side, most stickers are on the left. for a make/model number. ) The camper make, model and year too helps. Please tell us this as the older campers had different control systems then the newer ones.

Since you have and an "auto" light and a fault light, this suggests a newer vintage.

I'll explain a few things that stick out from your post assuming you have a Dometic fridge, the Norcold works similar.

1. Just so you know, the "fault" light is "only" for a gas lighting fault. It does not indicate any other fault within the fridge. The fault means the fridge did not light when it was supposed to, either at startup or when it was running on gas. There is a sensor that detects if flame is present when there is supposed to be a flame. If you have no LP gas turned on, and the fridge set to run on gas, it will go into fault for either trying to light and not lighting for 3 tries. Or the fridge did work, the flame was lit and then the flame went out as any residual gas in the lines ran out, the system will detect the flame when out, try to relight it, and after 3 failed tries, the fault will come on.

2. It appears after the power event at the campground, your fridge may have been affected. I'll ask so we can help confirm a few things.

When the park was having power issues, was the fridge on Auto or on gas only?

If it was on Auto, then it was running on the electric element which runs off of 120 VAC power. The control system is 12 VDC and runs the control systems, the gas part of the fridge and the light bulb inside the fridge compartment.

What appears now is, either the lower outside control board was affected by the power issue or the electric element was affected by low/high voltage.

Do you have a volt/ohm meter and know how to use it?

Are you OK with testing 120 VAC circuit? Or have a friend who can help you who is electrically friendly and knows the dangers of electrical?

The control board which is powered by 12 VDC, only turns on and off a relay that has a contact that switches the 120 VAC power to the electric element on and off. The heating element is 120 VAC, you give it power and it heats. The test is, is the control board sending 120 VAC to the element, yes/no? if it is sending power, then the element may be burnt out. If it is not sending power in Auto when it is supposed to, then the control board may be partly bad. Or you have both going bad.


The 5 amp fuse (again on a Dometic RM2652) is a 5 amp AC fuse
to protect the integrity of the AC heater circuit from shorts. Since you found that blown, something on the AC side was affected.

Not knowing what happened to the incoming AC shore power, if it dropped low, the amperage could go up trying to power the electric element, thus blowing the fuse. Or something went real high and burnt out the element. Or by coincidence the element shorted to ground.

If the testing confirms the control board is putting out 120 VAC to the element, but yet no heat, there is an Ohm check on the element to tell if the element is burnt open.

I did not explain yet how to do all this testing, just yet until we know you won't get hurt by doing it.

With you wiggling the connections, and things starting to work, there may be more issues yet to be discovered after you sort out the electric element part.

Hope this helps

John

[Wnaplay]

Thank you for the reply. I will double check the model number tomorrow for the fridge I have. I am fairly confident with a meter. I do own several and if the specifics are made clear, I feel I can follow directions of you tell me what to check. When the issue happened it was on in auto mode, gas switch turned off as well as tanks turned off. I will do the ohm test on the heating element wires in the morning and report back. What I dont understand based on your reply is why it would show a check light if it's set on auto yet the gas switch is turned off.

[JohnB]

When the fridge is in auto and on, the system will default to running the electric element, only if, the system sees 120 VAC on the control board. If the control board does not see 120 VAC, it will then auto switch over to LP gas automatically regardless if the LP gas button is turned off. So, yes you can get a gas lighting fault even with the gas button off.

The gas button when it is on, forces the fridge to run only on LP gas, no electric. The auto light will go out, but if you open the door, the inside cabinet light will be on. There is no pilot light indication that you are in gas mode only.

The ohms of the electric element are low. Like around 44 ohms. While you are checking, check each lead of the element to earth ground or DC ground at the terminal block. Sometimes the elements shorts to ground when they fail.

If you did not loose 120 VAC to the camper, or at the fridge outlet, then the controls board may have issues too sensing that you are supposed to be on electric and it is flipping over to gas.

Hope this helps

John

[Wnaplay]

I am good at checking the ohms but I am not sure what you mean by checking each lead to earth ground or dc ground.

[JohnB]

Hi,

Sorry, my shop talk is coming through on the grounding. Here are the basics of earth ground and DC ground.

When you have a moment, here is more on earth ground as it relates to your Sunline.
https://www.sunlineclub.com/forums/f...ock-11647.html

Earth ground is literally what the word means, The earth is a conductor of electricity and all the big power transmission sites actually have a wire going to a grounding rod into the earth. This is all part of a larger safety system to help prevent you from getting shocked.

At the camper, the NEC code rates and requires campers to be like a large electrical appliance, like a corded drill motor, a refrigerator etc. In the shore line cord there are 3 wires in the30 amp service you have. A black hot wire, live 120 VAC, a white 120 VAC neutral wire, and a green earth ground wire. Since the camper is made of a lot of metal, the camper steel frame, the siding, just about anything made of metal has an electrical path to earth ground. This is required as part of the shock hazard prevention system if the live 120 VAC hot wire ever touches metal on the camper, it helps protect you from being shocked and would trip the incoming fuse/circuit breaker.

At the fridge, the 120 VAC outlet has the 3 prong plug, there is an earth ground in that 3 prong plug that attaches to the metal frame of the fridge.

DC ground, this is a wording thing pending which industry you are in and what you are working on. Not all DC wired systems are connected to earth ground, as the voltage is low enough and the sensitive electronics can be affected by electrical noise on the AC ground system. And then there is other more common automotive DC ground or DC frame ground. In automotive they use the metal frame of the vehicle as a wire and they call it ground or frame ground. The DC negative (-) of the battery is connected to DC frame ground. Like the starter in your car for example.

There is also term DC ground or GND in the electronics world. They are referring to the DC negative on the circuit board and the circuit board may have nothing to do with 120 VAC or earth ground. This is sort of a low voltage DC thing that has been around longer then I have, we call DC ground or ground in a DC circuit, ground. It's an industry slang thing for DC negative.

Campers follow part of the automotive DC frame ground and part of the AC world earth ground. In your camper, earth ground and DC frame ground (battery negative (-) are tied together on purpose. The white cable on a Sunline battery is bolted to the frame of the camper. The electric brakes, the body lights, tail lights all use the metal frame as a wire. And since there is 120 VAC in the camper, that metal has to be earth ground connected. So, AC earth ground and DC frame ground, are common to each other and even called, the ground wire.

At the fridge, there is 12 VDC coming to the fridge. There is a black 12 VDC positive wire (+) and a white 12 VDC negative wire (-). We refer to the 12 VDC negative as DC ground.

The heating element is 120VAC, so the metal frame of the fridge has to have a earth ground connection to it. And since the fridge is DC, it also has a DC ground attached to it. There is a small bolt with a bunch of ground wires right near the incoming 12 VDC power wire.

Test for ohms/continuity from each heating element wire to that earth ground/DC ground wire junction. There should be no connection between either element wire and that grounding connection. If there is, the element is bad and needs to be replaced.

This post may help, the link will drop you into the middle of a big camper restoration post where the fridge electric element would short out to earth ground when it got hot. Some elements fail cold to ground, some take a little heat expansion to fail to ground, others just burn into an open circuit, (no resistance) https://www.sunlineclub.com/forums/f...tml#post154885

This reply may help on the ohm test of the element, for ohms and earth ground https://www.sunlineclub.com/forums/f...tml#post152689

Hope this helps

John

[Wnaplay]

So far I did the ohm test and if I did it correctly, setting my voltmeter to ohms, put each lead in a wire from the heating element, I got ol. I disconnected shore power before this test but I did not disconnect my battery or 12 vdc if that matters.

[JohnB]

Hi Wanaplay,

Before we declare your electric element is burnt open, need to confirm how you did the test.

1. Did you unplug the element from the control board to do the test? I'm assuming yes, if not we need to back up and try it with it unhooked from the board.

2. Did you test your meter by crossing the leads out in the open to see the meter go close to 0 ohms? The digital meter should of started at OL then go close a 0 ohms reading then back to OL when the leads where taken apart from touching. It might not ne exactly 0 ohms, but real close. This is a standard test any time you use an ohm meter, to make sure the meter, the leads and all are working. You are doing a basic continuity check of the meter by doing this. Assuming you did this, then the meter is setup right and working, if you did not do this, then retest.

3. If you made it past 1 & 2, you inserted the probes into the plugs of the 2 element wires, and if the meter shows OL on a digital meter, that means there is infinite resistance and no conductivity. When you see a test come out like this, it is standard practice to repeat no 2 test, to make sure the meter is still working, then do a retest on the element to confirm the reading is still OL. A 3rd time doing the retest is prudent too. There are times the meter leads do not make good contact in the wire plugs, so doing the retest helps confirm you had a good connection, it is just that the element is an open circuit.

If you made it through no. 3 and still have an OL on the meter, then your heating element burnt open. There is no repair to this, it is only replace.

Did you test the control board that it was sending 120 VAC to the element? This is a live power test and if this it too much for you, then do not do it. It appears the power outage issues may have aggravated a burnt out of your element. At this point, you do not yet know if it damaged the control board unless you tested that it was sending power to the element, just the element was burnt open so nothing will happen.


Did you get the make/model and year of the fridge? And your camper?

We can try to help and look up the element part numbers, but we need then info to help better.

Hope this helps.

John

[Wnaplay]

Dm2652lbx is the model of the fridge.
Ohm test on heating element wires = OL
Wire at j5 had 116vac
Pin j7= no acvoltage
Pin j8 no acvoltage

[Wnaplay]

I am wondering if the heating element is shot and the control board is fried, shouldn't it still be able to work on gas? I lit the gas and let it run but it never got cooler.

[JohnB]

Originally Posted by Wnaplay

Dm2652lbx is the model of the fridge.
Ohm test on heating element wires = OL
Wire at j5 had 116vac
Pin j7= no acvoltage
Pin j8 no acvoltage

Hi,

The DM2652 I'm not sure what year that was. The RM2652 I have done a good deal of work on. Both of those models are now discontinued by Dometic. I would have to dig deeper to see if I can find the differences between the DM and the RM models. I sense it may be a vintage upgrade difference. What year is your camper?

If the fridge was powered up, and in Auto, and no 120 VAC coming out of pin J7 & Pin J8, that points to you control board and the electric element are bad.

This site may help on part numbers. I have never bought from them, but use that as a part number reference.

Without knowing the differences between the DM & RM I am not totally sure of these parts I'm linking will fit your fridge. The upper control panel "might" be different.

The control board
https://pdxrvwholesale.com/products/...way-3308741002

The element
https://pdxrvwholesale.com/products/...att-3850644422

On the control board, Dinosaur electronics makes good boards https://www.dinosaurelectronics.com/

These 2 pics have the Dometic and the Dinosaur next to each other. The light green colored housing is the Dinosaur. The black case is the Domectic This is for an RM 2652





I would have no issuing using a Dinosaur board. This is the one I bought for my RM2652


Dometic obsoletes and upgrades parts so often it is hard to keep track of what is the latest replacement parts that supersedes the older numbers.

Hope this helps

John

[Wnaplay]

My fear is that I will start replacing parts and still end up with a fridge that won't cool. Is it likely the board and element are both bad at the same time? Before I order these parts should I make sure something else isn't also wrong? With these 2 things being bad should it still cool on gas alone?

[Wnaplay]

I called and spoke to a tech at dinosaur boards today. The heating element is definately done. The board we aren't sure about. I tested everything again and nothing seemed to work. After disconnecting and reconnecting some wires the board seem to come back to life and I lit it on gas and it's cooling. No idea why I keep losing dc power at the board for the gas or why it randomly begins to work again. I will order a new hearing element and see if it will work on electric as well. I don't know if the board is shot but works randomly or if just moving the wires permanently fixed it but the tech at dinosaur said that if they had an open neutral then it likely severely damaged every system in the entire camper.

[JohnB]

A few things that may help.

I can see that the AC side of control board can be bad while the DC side still works. The two voltages are separate.

The board uses the 12 volt DC to run the controls and the gas system. If the DC out out, nothing will work. But the AC side "only" deals with the electric element. I did not trace the circuit board, but in most cases they use a relay on the PC board in place of a triac to switch the AC power to the element. The control of the that relay is DC, but has AC on the contacts. If the element can be burnt out from high or low voltage and it may have got both. That surge in voltage or high amps may have burnt up the relay contacts, yet the DC coil to make the relay work, may still work, just AC power cannot pass through the relay contact. This would explain why you had no AC power on the 2 element pins on the board. Not sure this is what happened, but it would explain why the gas side of the board still works (it's all DC) and the AC element does not.

You talk about the board going dead, then wiggle some wires and the thing starts working again. The board could be bad, but there is another possibility of you giggling things. The DC ground (negative) has many wires all bolted to the plate next to the incoming 12 volt power. Corrosion on the ground wires, or even in the 12 volt DC terminal block for the hook up can be an issue. Point being, in the DC world, losing the grounds (negative) can stop everything from working. We tend to always think we are losing the positive 12 Volts, but the system will not work if there is no good connection on the 12 volt grounds. Clean up any corrosion fuzz you see on the grounding bolt/wire to the frame and the incoming terminal block. Wiggling the wire can make or break the connection.

The mechanics of the absorption fridge is simple enough that if you heat the boiler tube area, the fridge will cool. The big cooling coil is the heart of the system. If that ever springs a leak and you loose the fluid inside, that is a $800 plus part. The cooling coil survived the incoming AC power issue as it was not affected. The electric element and even the PC board are small costs compared to a new absorption RV fridge. There is only one other PC board in the fridge, inside up top where you the auto light and buttons are is another PC board. However if that board goes bad, then generally nothing works as it tells the rear main PC board to work. So far, that inside top board is not suspect.

You are doing well on this. Electrical surges are always a search and destroy mission trying to figure out what went wrong. By chance did you check the water heater and furnace? If they were off, they may have had a better chance of not getting damaged. The fridge, most times is on when you are camping.

The power converter can also take a hit pending what the surge did or did not do. Have you checked that the battery is receiving a voltage lift when the converter is plugged in? Check the battery voltage, 13.25 volts range is float mode, 13.65 V range is standard charge and boost (if yours has it) would be in the 14.4 range. If the battery voltage is down in the 12.7 or lower range when the converter is plugged in, then something is not working and the battery is keeping your camper alive. As FYI, 12.8 volts is 100% state of charge if you are on a lead acid battery.

Hope this helps and please report back what you find.

John

[Wnaplay]

I will check the battery charge tomorrow. If I heard the dinosaur repair tech correctly he stated I would never see voltage at the 2 element pins (j7j. I don't know what I would see if it wasn't 120vac. I never use the heater or hot water tank so I don't know if either of them were affected. I really never use any gas run appliances. I only turned the gas on to see if I could get the fridge to cool. The weird thing is 2 days ago I fired the fridge up on gas and it didn't cool. This time it did.

[JohnB]

Originally Posted by Wnaplay

If I heard the dinosaur repair tech correctly he stated I would never see voltage at the 2 element pins (j7j. I don't know what I would see if it wasn't 120vac.

H'mm, no voltage at the 2 element pins, well maybe dinosaur is using a triac and not a relay to switch the power. The triac shuts down the current, I recall a deep memory you can't test for voltage on the output of a triac. It's a real old memory so it may not be right. Not sure if Dometic uses a different switching system then dinosaur.

Thanks for passing this along. We all learn something from these trouble shooting events.

[Torskdoc423]

I'll 2nd the Dinosaur boards. Installed one in 2008 on a RM2611 and 2 yrs ago on my Rm 2652 (turns out both use the same board) so my spare from the 2611 went on the 2652. Suggest a slow speed fan inside. Moves the air around inside so you don't have a cold boundary low and a warm boundry high. During hot weather Maxing out the setting on the board , gets me down to 35*F and 4*F freezer with minimal opening of the unit now. Got an Amish made cooling unit for the 2652 early last year ($700 or so). No more problems with long long cool down times.

[Wnaplay]

I can't win. I ordered the new heating element but I have the type of fridge where the entire fridge needs to come out remove the shield to replace it. Then I order new pigtails for the l.p. tanks because I noticed 1 was leaking while diagnosing the fridge but I ordered the wrong thread size. Ughhhh

[JohnB]

Originally Posted by Wnaplay

I can't win. I ordered the new heating element but I have the type of fridge where the entire fridge needs to come out remove the shield to replace it. Then I order new pigtails for the l.p. tanks because I noticed 1 was leaking while diagnosing the fridge but I ordered the wrong thread size. Ughhhh

Hi,

Can you post a pic of the burner area? Odds are you may not have to take the fridge out completely, just most it out the cabinet about 6 to 12" to get some working room. That is not as bad as pulling the whole fridge.

Ideally, you do not have to take the whole burner stack off to get the element out.

Does the burner stack look close to this? If so, you do not have to take the whole stack sheet metal off, but need room to get in there and work on it. Moving the fridge ahead some can allow you to get in and change it. There is an access panel above the element that you take out of the whole stack shield.