Dometic RM 3804 will not work on batteries

[janeinthemtns]

I have a Dometic RM 3804 that works perfectly on propane. When I shut off the propane and turn off the fridge it continues to try to light the pilot when I turn it back on. I can hear it. The light is bright inside the fridge and all the l2v lights and fans are working fine throughout the trailer. What to try next? The battery condition still says fair on the control panel and I hooked up the second battery which had been disconnected. I still don't know if the solar panel is charging the battery.

[Aage]

Are you sure that model will run the cooling system on 12V?

My 2812 and most of the Dometics I have seen or read about are 2-way in the sense of using either 120VAC or 12VDC.

On the "Auto" setting, you described exactly how it switches over to 120VAC. The clicks, then one clack as it opens the 120VAC relay...

[DKB_SATX]

If you want an RV fridge that is effective on battery power, you'll need a Danfoss compressor model like a Dometic Tundra. Even if your model is a 3-way (which is unlikely, Airstream used 2-way models in trailers) it would eat a battery in short order and just manage to maintain whatever temperature it was at when you switched to battery, absorption fridges are too inefficient to be kind to batteries. Stick to 120v or propane operation with an absorption fridge.

[louaxtjr]

I believe the Dometic RM 3804 is indeed 3-way capable, like my RM660. 12v operation WILL draw a large amount of power. That said, it sounds like a problem with the connection to power or in the control circuit.

[daveswenson]

Looking at this site it looks like the 3804 could be configured either 2 or 3 way.
http://www.dinosaurelectronics.com/Dometic_Chart.htm

[janeinthemtns]

It's a 3 way. It was installed by the PO. I was thinking if my solar panel is working, I might be able to use it 12v. I haven't plugged the Airstream into the house current yet. Still trying to figure things. out! I was looking for an owners' manual on line, but all I can find is a service manual. Thanks for those replies. It's possible the batteries have discharge to such an extent that they won't run the fridge. I don't know how to tell if the solar panel is working. I don't know if the control panel assessment of the condition of the batteries is accurate. It said Good, now it says Fair. Lots of sun. If the panel was charging the batteries, I think it would say Good again.

[daveswenson]

I think the first thing I would do is check the battery voltage with a multimeter, I don't trust the monitor. I'd also have the batteries load tested. It might be time for new ones.

[DKB_SATX]

Do you know for a fact that it's set up for 12v operation? (Even if it's built for it.) If I remember correctly from reading a post about 12v absorption operation (I think written by Lewster) that there are 2 sets of 12v inputs, one for the control board and one for the heating elements.

[janeinthemtns]

Thanks so much for all those ideas. I was hoping I could run it with the solar panel. Still trying to figure it out.

[lewster]

12VDC resistance heating is the least efficient of all 3 heat sources found in an RV 3-way fridge. And to compound the problem, the 12VDC heating element was designed to minimally heat the gas/absorption mixture, which AT BEST will maintain your fridge temps once it has been cooled by either of the other 2 heating methods.

As it is for maintaining interior fridge temps, you will start to see a rise in those temps every time you open the fridge door when in normal use. A 12VDC heating element draws approximately 10 amps, which is a significant draw down on your batteries.

I don't know what size your solar array is, but a typical 200 watt solar array with an MPPT boost charge controller will provide around 10 amps during 'solar noon' for approximately 4 hours, and will taper off dramatically as the sun rises and sets. That will give you, at best, 60 amp/hours into your batteries in a totally clear day, or 6 hours of fridge run time when on 12VDC operation.

So you have your day operation covered, what happens when it gets dark and there are other demands from your battery bank. Depending on the size of the bank, you might draw it down to 50% depth of discharge and when you start the next day, your batteries are at 12.2VDC, your solar will only provide enough amperage to run the fridge and nothing to re-charge your batteries.

It's a bad deal all around! Of course, you didn't specify the size of your battery bank or the size of your solar array. It can be done with the right sizing of teh system, BUT THAT'S WHAT LP IS FOR! Far more efficient as a heating source for your RV fridge............

[overlander64]

Greetings janeinthemtns!

Originally Posted by janeinthemtns

Thanks so much for all those ideas. I was hoping I could run it with the solar panel. Still trying to figure it out.

I have a Dometic 3-Way Refrigerator in my '64 Overlander, and am thrilled with its operation. What I have learned over the years is that the 12-Volt-DC operation is best for travel days . . . I always lock mine into 12-Volt-DC just prior to breaking camp. When I am trying to conserve LP gas during daylight hours while dry-camping, I have switched to inverter power to operate the 120-Volt-AC element on the Dometic with good results when the three solar panels on my Overlander are in the sun . . . but this is only practical during daylight hours as the three AGM batteries would be quickly drained by the inverter after sundown (this is something that I only due if I am afraid of running out of LP before my planned departure).

Good luck with your investigation!

Kevin

P.S.: Something else to check is for the gauge of the 12-volt supply wire running to your 12-volt heating element . . . this was one of the areas that the installer of my Dometic 3-Way was very particular about as he indicated that the wire had to be a heavy gauge as it had to run 3/4 of the way around my Overlander to get to the 12-volt power supply panel. It is also possible that there is a blown fuse in the 12-volt power supply that is keeping your Dometic from working on 12-volt.

[janeinthemtns]

That's a load of information! Thanks a lot. I don't know what size solar I have. I believe it came from the factory. It is hooked up to a little box at the back vent with red lights saying it's charging, but now my batteries are dead with nothing running in the trailer and a lot of sun. I need to concentrate on getting a seam sealed. There is one small leak in the trailer. And getting the painting done while it's still hot so the paint smell can be gone before I live in it this winter. I can always plug it into the house. I am spending a lot of hours researching every little thing and I'm so remote I either have to order from the internet or drive 50 miles to town. It's like a full time job!

[janeinthemtns]

My ultimate plan is to have a good sized solar array on the ground so I can keep the snow off of it. I can see that is going to be far off from where I am now.