Dometic Refrig Reignitor - Fiberglass RV


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Old 05-27-2014, 06:30 AM   #1
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Dometic Refrig Reignitor

Here’s one for those who have the small Dometic refrig. I have the Dometic RM2193 3-way fridge. Gas (with a spark button), 120 vAC and 12vDC. It drains the trailer battery during a long tow as the Flex doesn’t put out enough amps to counter the 10A DC the refrig uses. The net result is that it doesn’t keep the contents cold during the trip.

I’ve tried running it on propane while travelling and the buffeting blows out the gas light.

While I was looking into adding a reigniter (like I did on the 1-way Suburban water heater, Water Heater Re-ignitor ) it occurred to me that there already was a “sparker” at the burner end that fired off when you pressed the button on the control panel. And you usually can’t tell at first whether the gas burner has lit as the light is hard to see through that little opening in the daylight. And it takes a while before the flue heats up enough to feel warm.

I wondered if I could just put in a Suburban electronic reigniter control and splice it into to the wire going to the burner sparker avoiding taking off the burner box.

The answer is “yes” and it was an easy mod.

I used Suburban’s reignitor kit (~$60) no. 520790 (http://www.amazon.com/Suburban-520790-Re-Igniter-Kit/dp/B007HRWQTC/ref=sr_1_1?ie=UTF8&qid=1401188745&sr=8-1&keywords=suburban+reignitor+kit).

I tapped into the 12vDC available at the back of the refrig; cut and soldered on narrow (~1/8”) female and male spade connectors (I put the female connector on the wire from the sparker and a male tip on the wire to the button in case I wanted to revert to the stock configuration); found a ground and I was off and running. You’ll want to solder the connectors on the sparker wire as it’s a very fine single strand wire and normal red (18-20ga) connector won’t pinch the wire. The sparker unit has small male posts for the wiring thus the 1/8 connectors.


All this without disturbing/replacing the existing sparker other than cutting the line and adding the connectors. Although it assumes that the current sparker is working. And choose carefully where you cut the sparker wire to give yourself enough slack to add the connectors and to hook the sparker end to the control module.

The reigniter stops sparking when the pilot lights. You still have to press down the high-med-low dial to first light it but the sparker will start again and reignite the burner if the gas light goes out. The theory being that if the buffeting blows out the burner, the reigniter will immediately relight it.

Next up is consideration of some sort of baffle for the burner area that doesn’t hinder the normal convection needed for cooling that just sits there but can easily be removed without tools for operation at the site. I saw one on Joe and Mary’s trailer at Turkey Run that will be a probable starting point.

So, is this mod necessary? Of course not. Wretched Excess is the catchphrase for Castle Pretentious.
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Old 05-27-2014, 06:41 AM   #2
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Also sounds like a great way to get rid of the Push Button sparker, but what happens with the reignitor if the flame safety valve releases before it re-lights?

And do you need an ON-OFF switch in the circuit?
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Old 05-27-2014, 06:45 AM   #3
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The reigniter kit has an on/off switch on the "board". If it took too long to reignite the board would just keep sparking until you turned it off. The sparker uses 0.1A DC. Not a huge load. I've used the water heater unit for 9 years and it runs for it seems like 10 minutes before the gas gets back there so the unit seems pretty robust.

Other kits I saw used a 9v battery, which I considered but decided I'd rather a hard wired kit. Just my preference. The heater uses a little over 10A DC and it's on a 15A fuse at the panel. The igniter is on the same circuit.

For the moment I've left the button alone. Both as backup and it doesn't take any room to speak of.

This mod also meets my requirement to make no mod that if it fails, I can't go camping.
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Old 05-27-2014, 09:28 AM   #4
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More is less

Steve,

I had to read your second sentence a couple of times regarding using the 12v option on the refrigerator while driving and recharging. "It drains the trailer battery during a long tow as the Flex doesn’t put out enough amps to counter the 10A DC the refrig uses." Ah ha, so that’s why the sky is blue!

Last weekend I left Denver with a battery reading of 12.5v, the frig on 12v cooling, and the cable hooked for recharging while driving to Cheyenne, WY. This was the first trip after a recently installed charging line from the TV. I figured I would arrive in a couple of hours with the food still cool and the battery voltage topped off at 12.6+. It would be a good test of the system.

When I arrived, I checked the voltage and saw it was now at 12.4v. Whatttt?? I checked all the connections again and they all showed a reading of 13.6 volts on the charging line right up to the battery. How can you end up with less when charging more?

Now I see it was not recharging amps at a rate at least as high as the frig usage rate even though it showed high charging voltage rates. If that is true, then when using the frig on 12v while driving, you really need to have a recharge system for when you arrive and switch over to propane in order to restore the battery fully. Either shore power to a battery charger, solar, a generator, or leave the trailer hooked to the running TV for a while to recharge the battery.

It would seem that actually the longer you drive the less power remaining in the battery, which is just the opposite of what I was expecting. Is it just me or is something else missing?
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Old 05-27-2014, 09:48 AM   #5
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Actually the alternator puts out more than enough current to charge both batteries, but here's what happens:

1. The wire in the charging line is somewhat restricting as are the connections at the 7 pin connector, thus you will slightly restrict the current flow to the coach battery.
and the biggie:

2. The TV's charging system is designed to slow down charging as you reach fully charged condition. But it is reading the combined voltage of both batteries, as the TV battery quickly recovers the charging system will see the average voltage as higher than just the coaches battery and start to cut back on charging voltage/current before the coach battery is fully charged.

Remember in the "Old Daze" when cars had amp meters. Right after you started the amp meter would indicate high current flow to the battery and gradually reduce current as the battery charged. Car makers went to voltmeters because it was easier and cheaper than installing a shunt for an amp meter

3. The refrigerator doesn't care where it gets it's power, the battery or the charging line, so it sucks down the battery as that's the easiest source of current.

In some mini-motorhomes I have worked on this problem was solved by adding a 2nd alternator for the coach battery(s) alone. A GM single wire alternator did the trick.
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Old 05-27-2014, 10:13 AM   #6
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Originally Posted by Scamper Jim View Post

It would seem that actually the longer you drive the less power remaining in the battery, which is just the opposite of what I was expecting. Is it just me or is something else missing?
Nope not just you Its pretty well the same story for all of us with fridges that can run on DC. #1 reason I don't run mine on DC when traveling for more than a hour or so and especially if I am going to be dry camping at destination and in need of a fully charged battery on arrival.

Cool the fridge down well before taking off and don't put any warm food into it and put a couple of smallish freezer packs beside your dairy products and on your meats etc just before leaving and don't open up the fridge while traveling and it will keep cool enough for the food to remain safe for a number of hours of travel.... I keep a couple of freezer packs in the freezer compartment for this purpose and used them in some pretty hot weather without a problem.
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Old 05-27-2014, 10:17 AM   #7
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Originally Posted by Bob Miller View Post
Actually the alternator puts out more than enough current to charge both batteries, but here's what happens:

1. The wire in the charging line is somewhat restricting as are the connections at the 7 pin connector, thus you will slightly restrict the current flow to the coach battery.
and the biggie:

2. The TV's charging system is designed to slow down charging as you reach fully charged condition. But it is reading the combined voltage of both batteries, as the TV battery quickly recovers the charging system will see the average voltage as higher than just the coaches battery and start to cut back on charging voltage/current before the coach battery is fully charged.

The amount of power the TV has to push to the trailer battery can also be impacted by what is in use in the TV at the time.... ac, radio, xm radio, gps, iPad or phone chargers, rear video being used to watch movies all take away available power to the trailer as well.
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Old 05-27-2014, 11:11 AM   #8
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Excellent, thanks Bob for the explanation.

Both are new batteries so the difference in voltage between them would be small when averaged as you indicated.

So the moral of the story seems to be that you can't expect a charging system from your TV to fully charge the camper battery. You could arrive expecting it to be fully charged, when in fact it could be 10% or so discharged already from use along the way, and not even suspect it!
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Old 05-27-2014, 11:33 AM   #9
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I pretty much described what I know is going on in my trailer/tow combo. I made a test box that slips between the trailer and tow vehicle with an ammeter in it. I've shown this before but practically no one searches anymore so this will be like new news. The box shows what's leaving the tow (at a fast idle) going to the trailer with the fridge on 12v. 4.2A in, so a net 6A out of the trailer battery. After a 5 hour trip losing 6A an hour the battery monitor in the trailer is flashing "LO" at me. (as much a function of what I set as the discharged level on the meter)

All I know is that in a stone-stock tow package, my Ford doesn't nearly match the output due to the fridge.

Your mileage, or perhaps your amperage, may vary.

Trick battery isolators can change the numbers but I'm not inclined to go that path.

BTW, I don't travel with the box in the line, I don't need to with a battery monitor, but it's something I can bring to another's camp site to settle arguments.
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Old 05-27-2014, 11:42 AM   #10
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Originally Posted by Scamper Jim View Post
Excellent, thanks Bob for the explanation.

Both are new batteries so the difference in voltage between them would be small when averaged as you indicated.

So the moral of the story seems to be that you can't expect a charging system from your TV to fully charge the camper battery. You could arrive expecting it to be fully charged, when in fact it could be 10% or so discharged already from use along the way, and not even suspect it!
Ya, But, You are trying to bring a low coach battery up to full, the TV battery "tops off first and the charge rate starts falling It's really not much to do with the age of the batteries, but that they are two somewhat different batteries as well and charge slightly differently.

When charging banks of batteries it is essential that they all match to get an even charge. An RV Battery and the TV battery are far from being a match from the gitgo.
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Old 05-27-2014, 12:16 PM   #11
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Originally Posted by Scamper Jim View Post


So the moral of the story seems to be that you can't expect a charging system from your TV to fully charge the camper battery.
Actually you can! Assuming you don't have anything eating up more battery power than the tug can supply running in the trailer while towing.

I dry camp a lot and I count on the TV to recharge the battery to full while moving from place to place... it does it all the time providing their is nothing running in the trailer thats pulling more than a very small amount of DC.... a fridge does not fall into the small draw category.
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Old 05-27-2014, 12:46 PM   #12
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Iíve tried running it on propane while travelling and the buffeting blows out the gas light.
This is not normal, and should itself be fixable. The only times I've ever had that happen on my almost-forty-year-old three-way is when I've forgotten to close the little cover that shields the flame from the wind.
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