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Old 03-10-2018, 08:01 PM   #1
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Dometic refrigerator won’t run on shore power& water heater light on when on shore po

Hi all,

This is a confounding confluence of two separate problems, which may or may not be related. My Dometric refrigerator will not run on shore power, despite the fact that the coach is plugged in to shore power. The air conditioner will run fine, showing the coach is getting shore power. Both lights above the temperature on the top of the unit are lit, indicating the refrigerator is running on propane. Only the light on the left should be lit, indicating sure power.

At the same time, the electric hot water switch is on and the light is on solid red. It should not be on after the “try” light flashes. The mechanic switched out the converter, but that didn’t make any difference. No breakers are tripped, nor is the fuse for the refrigerator blown.

Do you think these problems are related? Do you have any suggestions as to how to solve either one? Many, many thanks to this supportive community.

Ron
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Old 03-10-2018, 08:22 PM   #2
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My fridge has a propane switch so it can be forced to run from propane. If yours does, make sure it is off.

Go outside to the fridge access panel and look inside. There is an electrical outlet there and a power cord from the fridge should be plugged into it. Make sure the outlet has power. If there is no power there, a circuit breaker in your AC panel may be tripped.

If the fridge is set properly to run on shore power (propane switch off), there is power at the outlet in the rear and the power cord is plugged in, the control board may be bad.

The water heater can use propane and shore power at the same time. It sounds like it is trying to run on propane and is not lighting. Do you have hot water? If so, the electric heater element is working as it should. Have you tried to re-light the heater by turning the propane switch off and back on a couple of times? If it still doesn't light, the burner tube may be clogged with insect debris, the igniter may be mis-adjusted, or the control board may be bad.

Al
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Old 03-11-2018, 06:47 AM   #3
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Dear Al,

Thank you for your thoughtful, generous and prompt reply.

Let's take the refrigerator first: the electrical outlet in the outside refrigerator panel works; it successfully illuminated a power strip with a light. No breakers are off on the controller panel, but I reset them anyway, with no difference. The only "propane only" switch I am aware of is in the freezer, where you can elect to run the refrigerator on propane only. In my case it is set to choose shore power if it is available, with a resulting one light, and run on propane if it is not, with two lights. Despite being on shore power, it is nonetheless displaying both red lights above the temp on the front of the freezer, which equals propane. Given that the controller was replaced as part of the process of trying to solve these two problems - without success - may I conclude you believe the next step is to replace the control board for the refrigerator?

As to the water heater, I apologize for leaving out some key facts. The control board for the water heater was replaced in an unsuccessful attempt to solve the problem of the solid red light. I checked in response to your question and I DO have hot water in the electric water heater on position. The gas control works quickly and well. So I guess the problem is not that I can't heat water, using either electric or propane, but that for some reason the red light stays illuminated when in the electric on/gas off mode. Does this help refine your analysis and advice?

Many thanks, Al!
Ron
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Old 03-11-2018, 07:15 AM   #4
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The cooling system of a RV fridge works the same on either propane or shore power:

A heat source(a small flame on propane, an electric heating element on shore power) heats an ammonia based refrigerant. This hot, pressurized substance flows through coils and small oriffices and looses pressure, absorbing heat in the process.

If the fridge works on propane, this indicates the cooling system is functioning properly.

I would suspect the electric element has failed. It can be found near the burner assembly. It has two rather large wires and is mounted in the chimney.

To test, disconnect power (unplug 120 plug from the outlet near the fridge) and remove the element leads from the control board. With a volt/ohm meter, test across the leads. There should be 40-50 ohms, if the meter shows no ohms, the element has failed.

If the element does show 40-50 ohms, the problem is probably the control board relay.

As for the water heater, the red light for propane is an indicator that the flame detector has has been heated by a functioning burner when operating on propane. If the light stays on even in the off position, I would suspect a wiring problem.

If it comes on only when turned on, and the water heater is heating on propane only, the thermocouple that serves as a flame detector has failed.



Regards,


JD
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Old 03-11-2018, 07:19 AM   #5
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Quote:
Originally Posted by fotoman1527 View Post
Dear Al,



Thank you for your thoughtful, generous and prompt reply.



Let's take the refrigerator first: the electrical outlet in the outside refrigerator panel works; it successfully illuminated a power strip with a light. No breakers are off on the controller panel, but I reset them anyway, with no difference. The only "propane only" switch I am aware of is in the freezer, where you can elect to run the refrigerator on propane only. In my case it is set to choose shore power if it is available, with a resulting one light, and run on propane if it is not, with two lights. Despite being on shore power, it is nonetheless displaying both red lights above the temp on the front of the freezer, which equals propane. Given that the controller was replaced as part of the process of trying to solve these two problems - without success - may I conclude you believe the next step is to replace the control board for the refrigerator?



As to the water heater, I apologize for leaving out some key facts. The control board for the water heater was replaced in an unsuccessful attempt to solve the problem of the solid red light. I checked in response to your question and I DO have hot water in the electric water heater on position. The gas control works quickly and well. So I guess the problem is not that I can't heat water, using either electric or propane, but that for some reason the red light stays illuminated when in the electric on/gas off mode. Does this help refine your analysis and advice?



Many thanks, Al!

Ron


Correction to my reply: I meant to say the converter box was replaced as part of the effort to solve both problems, not the “controller;” the only control board that has been replaced is for the water heater. I have not tried replacing the control board for the refrigerator yet. That may be the next step. Similarly, I was referring to the converter panel and it’s fuses- not the “controller panel.” Sorry for the errors!
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Old 03-11-2018, 07:21 AM   #6
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Quote:
Originally Posted by fotoman1527 View Post
Correction to my reply: I meant to say the converter box was replaced as part of the effort to solve both problems, not the “controller;” the only control board that has been replaced is for the water heater. I have not tried replacing the control board for the refrigerator yet. That may be the next step. Similarly, I was referring to the converter panel and it’s fuses- not the “controller panel.” Sorry for the errors!

Here are two pictures to further explain my response to Al.

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Old 03-11-2018, 07:32 AM   #7
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I beleive both indicators stay on in the auto mode, no matter which power source is being used.

The 120 volt source is treated as priority, that is why the the choice is between auto mode and gas only.



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JD
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Old 03-11-2018, 09:48 AM   #8
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Thank you, Jeff, but historically on our unit when shore power is the source of electricity only the upper left red light in the photo I previously attached is on. That's what is so confounding, along with the as-yet-unresolved issue of whether the refrigerator issue is related to the issue with the water heater.

The attached 3 pictures from the Dometic RM 3762/3962 manual support our experience and expectation that if the unit is running on shore power only the upper right light will be lit.

The fridge and freezer are both cold, so that should be of some assistance in locating the malfunctioning element in this puzzle!

Thanks again!
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Old 03-11-2018, 10:09 AM   #9
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As my experience is with older units, I'll let those who have experience with the newer ones continue to guide you. As to the fridge, the heating element test should distinguish between it and the control board.

Al
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Old 03-11-2018, 10:22 AM   #10
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Dear Jeff, please let me respond to your much-appreciated thoughts, below:

[QUOTE=jdalrymple;2075475]

"I would suspect the electric element has failed. It can be found near the burner assembly. It has two rather large wires and is mounted in the chimney."

I couldn't locate it, and have attached the schematic in case it is referred to by a different name there.

Further, I just ran the diagnostic test shown in the attached photo, and got no reading at all after it said AC and also when it said DP, meaning "AC heater is off. AC is not available." and, respectively "D+ low." (see manual excerpt below).

Does that help with the analysis?

___

"As for the water heater, the red light for propane is an indicator that the flame detector has has been heated by a functioning burner when operating on propane. If the light stays on even in the off position, I would suspect a wiring problem.

If it comes on only when turned on, and the water heater is heating on propane only, the thermocouple that serves as a flame detector has failed."

So to be clear, the water heats whether the electric or gas source is elected by the adjacent rocker switches on the panel in the bathroom shown in a prior photo. The red light stays lit only when the water heater is on electric.

Does that change your conclusion that the flame detector has failed? No one has changed the wiring, other than to replace the control board in a failed attempt to solve the problem.

So many thanks!
Ron
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Old 03-11-2018, 10:47 AM   #11
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Perhaps this wiring diagram can help me locate the "heating element" described thusly:

"I would suspect the electric element has failed. It can be found near the burner assembly. It has two rather large wires and is mounted in the chimney."

Sorry, but it's not evident to me! I plead ignorant, but anxious to learn, and grateful for all the help!
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Old 03-11-2018, 10:57 AM   #12
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The electric element for the fridge is referred to as the heater in the drawings.

From your posts, if the outlet near the fridge is suppling power, I would suspect the “heater” first, then the control board. It seems the board “sees” that the electric heater is not functioning and is switching to gas. All control of the choice of heat source, as well as the control of the propane burner, is handled by the board with 12 volts. The 120 volt AC is switched on and off by the control board and serves only to provide heat via the element.

Test the element.



Water heater: so the red lamp on the propane switch illuminates when the 120 vac is activated?


Regards,


JD
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Old 03-11-2018, 11:00 AM   #13
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The heat shield and insulation must be removed to access the element.
The element fits inside a tube along side the boiler.
Follow the wires labeled heating element.
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Old 03-11-2018, 11:09 AM   #14
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Item K in the last drawing.

Leads P3 and P4 on the control board.




Regards,

JD
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Old 03-11-2018, 11:20 AM   #15
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Our Dometic quit on shore power due to failed heater. It did not switch to propane. Control board apparently thought everything was peachy as AC power was detected and 12V power was available for board and indicator lights.

Used ohm meter to diagnose, got new heater for $40 on Amazon, easy fix!

Good Luck with yours!

Paul
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Old 03-11-2018, 11:57 AM   #16
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[QUOTE=jdalrymple;2075573]The electric element for the fridge is referred to as the heater in the drawings.

Water heater: so the red lamp on the propane switch illuminates when the 120 vac is activated?


The issue isn't with the propane switch, JD. It's with the electric switch to its left, on the other side of the light display. When the electric rocker switch is turned on there is no red light. After about a period of time - sometimes hours -in the on position the red light comes on and stays on, all the while providing hot water. From prior use of this unit that is not normal. The red light should not come on and stay on. The most it should illuminate would be a brief flash of the red light, called a try light, when turning the electric source on. Again - the water is heating with both electric and gas sources, and the control board for that unit was just replaced as part of the process of trying to figure out why the red light comes on after time and stays on, a behavior I'm trying to stop.

I'll respond to the refrigerator panel separately.

THX!
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Old 03-11-2018, 12:05 PM   #17
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I'm so sorry; I thought I had posted a picture of the water switch issue. This should make it clear: the electric switch is on; the gas switch is off and the red light stays lit. The yellow circle is 'ON." THX.
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Old 03-11-2018, 12:51 PM   #18
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[QUOTE=jdalrymple;2075475]

"I would suspect the electric element has failed. It can be found near the burner assembly. It has two rather large wires and is mounted in the chimney.

To test, disconnect power (unplug 120 plug from the outlet near the fridge) and remove the element leads from the control board. With a volt/ohm meter, test across the leads. There should be 40-50 ohms, if the meter shows no ohms, the element has failed.

If the element does show 40-50 ohms, the problem is probably the control board relay."


I disconnected the heating elements and put one probe on one element and the other probe on the other element. It measured 43 ohms.

I take it JD you feel that means the electric element has not failed, and that the control board relay needs to be replaced.

If so, I don't see anything labeled "control board relay" on appendix C-wiring diagram {already uploaded}.

So am I correct in assuming you mean "A - control board" from that diagram?

If so, is that a complex replacement? Thanks so much!!!
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Old 03-11-2018, 02:19 PM   #19
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There is a fuse for the heating element, I had to replace mine for the fuse fell apart. The ends came off.
Hot temps 100 + has caused this fuse to fail too, running on gas works "better" for me in high heat than 120AC.
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Old 03-11-2018, 02:37 PM   #20
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43 ohms would mean the heater is good.

That would point to a control board failure, seems to me. I wouldn’t try to repair components on the board, just buy a new board.

I am not familiar with water heater controls you posted. But, I have never seen a red lamp that has anything to do with the 120 vac heat element.

You are correct in the function on gas. It lights briefly when the gas valve opens and the burner lights. The lamp goes out when the thermocouple detects a lit burner. If the burner goes out before the high temp limit is met, the thermocouple cools and tells the board the flame went out which switches on the lamp to indicate a fault.

I would wonder if something is wrong with the limit switch and the lamp is indicating an over temp error, as it seems you have hot water.


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