Fridge not cooling well on LP - resolved

Gene · 08-28-2013, 10:04 PM

Sorry this is so long but it may help someone else dealing with this problem.

Recently my Dometic RM2652 fridge has not been cooling well on LP. It took a lot longer to cool on LP than electric. Often running on LP while on the road the box would show over 40 degrees on my wireless thermometer and it would only get down to 34 or 35 degrees. Running on electric it would always stay in the range of 32 to 36 degrees per the High/Low readings on my wireless thermometer even on the hottest days. The "obvious" fix in that case is to clean the burner and jet. I had already done that in the Spring but I did it again anyway ... twice. Jet was cleaned by soaking it in alcohol and burner was cleaned with a long Q-tip soaked in alcohol. Did not get any better after that.

I had just replaced the vent cover this Spring so I knew there were no nests or gunk blocking the vent or the fins but wondered about cleaning the flue (that tube just above the burner that carries heat to the "boiler") and flue baffle. (the baffle is a 5 inch long piece of twisted metal that sits 1 7/8 inches above the burner and hangs in the flue on a long stiff wire) Dometic does say the flue should be cleaned yearly but some people say they have never cleaned the flue. OK, next step is clean the flue and check the baffle. I removed the vent cover, cut away part of the screen at the top, used a coathanger wire to reach down and pull up the baffle hanger wire. The baffle was a bit rusty so I cleaned it with fine sandpaper. I had a piece of moderately stiff wire that I could use to push a cleaning rag up the 3/4 inch flue. The flue was clear with only a little rust and carbon. I put the baffle back in the flue and put the burner back in place. (needed to remove the burner to poke the rag up into the flue) I measured to make sure the baffle was the correct distance above the burner. With everything back together it was not any better. I looked at the flame in the burner and compared it to pictures I had taken a couple of years ago when I had the same problem. The flame on the burner looked good but not really fat.

At this point I decided to order a new burner and jet and wait the few days it would take to arrive. While waiting I had nagging thoughts about gas pressure but everyone knows that gas regulators never go bad ... do they?

The only way to measure the gas pressure is with a manometer. The burner has a handy test port built in to connect a manometer so I headed off to Home Depot to get the parts to build one myself using the test port plug as a sample to get the right pipe sizes and some plastic tubing. The Dometic manual says the correct pressure is 11 inches WC (the amount of pressure required to raise a column of water 11 inches) with 1/3 of the BTU load turned on. Below is a picture of my homemade manometer, it cost a little under $12.

I turned on the fridge and measured the height of the water column. WOW!, it was a whole 8 inches and when I turned on a stove burner it dropped even lower. Time to see if the regulator can be adjusted. I have a Marshall 250 series auto changeover two stage regulator. I did find that the regulator can be adjusted. The Marshall has a black cap on the low pressure half that can be unscrewed and inside it a black disk with a hex opening for an Allen wrench. I found an online comment that one turn would raise the pressure 1/2 inch. Working slowly and watching the manometer I got the pressure up to 10 1/2 inches WC.

The fridge now cools as well and as fast on LP as it does on electric. While I was doing test runs my new burner and jet arrived so I installed them too. Time for a new regulator since this one can not be trusted. Unfortunately Marshall Gas Controls and the parent company S.H Leggitt Company of San Marcos, Texas, has been in bankruptcy twice and ceased operation as of December 2012 so an identical replacement is not available.

Here are the parts used to make the manometer. You can see the Allen wrench I used to remove the test port plug. The larger 1/4" threads are wrapped with yellow (gas) teflon tape.

Watts Brass Pipe Nipple 1/8" - LFA-715
Watts Brass Pipe Coupling 1/4 FIP x 1/8 FIP - LFA-734
Watts Hose Barb 1/4 ID x 1/4 in MIP - LFA-192

The manometer hanging from the fridge opening. The plastic tubing was just tied to a metal pole I had then water added to a level half way up both sides of the tubing. With the fridge on measure the difference between the water level in each side, that is the Water Column height. As you can see it is a real "high tech" device.

**Sunline Fan** · 08-28-2013, 11:18 PM

Mind=blown

Nice work, Gene!

bunjin · 08-29-2013, 12:37 PM

Gene,

Nice post. Thanks for the pictures. Does a great job of showing your sophisticated manometer.

Just out of curiosity do you know when after adjusting the regulator flow if it had any change on your furnace, gas range, oven, etc.?

Gene · 08-29-2013, 06:00 PM

I haven't tried the furnace or the water heater yet. ...Too hot for the furnace and I didn't have any water in the water heater so I will try them this weekend. The stove does have a more "healthy" flame and burns clean and blue.

Gene · 08-30-2013, 08:30 PM

I connected the water and fired up the water heater today. Fired up on the first shot.

Big flame and a bit more yellow way inside at the tip than I thought was good. The air shutter was only half open so I opened it almost all the way and had only a little yellow on the tip.

In the Spring when I tested the water heater it took almost an hour on gas to get from cold to hot and then shutoff. Today took a little over 1/2 hour and I had warm water in the first 5 minutes. Probably would have heated to shutoff faster if I didn't keep turning on the faucet inside.

It was 80 degrees inside the camper, too hot for trying the furnace.

bunjin · 08-30-2013, 08:35 PM

So far seems everything was starving for gas.

**JohnB** · 09-01-2013, 12:53 PM

Gene,

You have done a great job of troubleshooting and found the problem. Good for you.

Let's compare notes as you have been into an area I have not yet. The flu baffle. I know you are a picture kind of guy... Got any of this? I know Dometic has it in their manual to clean that baffle annually. Yet the roof vent, again a Dometic, has no access port to make it practical to do annually. Ideally they create a screw on screen access port so you can remove it and reach down in verse cutting the screen or undoing the entire roof vent off the rubber... And that is not going to happen on most any camper annually. What would they expect the folks do who have the fridge in a slide? Remove the fridge from the cabinet each spring? Need a practical way to get to the baffle.

Now to your regulator. Heads up, your regulator may be on it's last leg. I had one that was low too. And once adjusted it works but then what ever made it drift in the 1st place can rear it's ugly head and go the other way, too high and that is not good. You should check your lock up pressure and make sure it is not going too high. And long term, (actually in the near future) be looking for a new regulator.

With Marshall going under, again... an exact replacement may not exist. I have not seen anyone pick up their product line yet. I found this one by Olympian Item and maybe an option

on Amazon Camco 59005 RV Propane Double-Stage Auto-Changeover Regulator : Amazon.com : Automotive

It is close possible replacement, the only down side I can see is the red green indicator is in the lever. With my tank cover it is going to be harder to see it, I think.

If you have the older lift off cover, then no problem.

Also heads up if you get one that the pigtails you have the flare fitting ends on the regulator. Some have the flare fittings, others use NPT thread. Just need to get the right one for your hoses OR get the adapter fittings.

This link may be useful if you did not know or remember it on the lock up pressure test.
http://www.sunlineclub.com/forums/f7...cks-10981.html

Thanks for posting your saga. It helps many.

Thanks

John

jim44646 · 09-01-2013, 03:57 PM

I sure like your propane cover. Wish they still made those. I took my flue baffle out a while back.
it's so cramped in there it would be hard to get a photo. I used a mechanics tool retriever to grab hold of the el shaped wire and pulled it straight up. After all that it wasn't that bad. The reason I pulled it was I had the refrig vent cover off installing a couple computer fans on the wire mesh for coil cooling.
http://www.toolbarn.com/ampro-t19602...FWNgMgod0iUA-Q

Gene · 09-01-2013, 07:48 PM

John,

Regulator:
I already figured the old regulator was toast. After I got the 8" reading I turned on a stove burner and watched it drop to 7". That told me the regulator was not regulating.

I spent a lot of time with my friend Google and found my reglator could be adjusted so I had to try. I did see posts where people said Marshall had shipped a lot of them preset to 8" but since the fridge was good last year I knew it had to be dying.

Seems there are only 3 choices for auto changeover 2-stage regulators since I can no longer get the Marshall like my current one with the window on top to see the red band.
* Marshall Excelsior MEGR-9984P (not the same company as Marshall Gas)
* Cavagna which is also sold as Mr. Heater. Several sites show a glass dome version where you can see the red from the top. Cavagna stopped making that version before 2009.
*Camco 59005 - the link John posted above

I replaced my tank cover last year with a dual 20# cover with the door at the top but not near as nice as John's. All the above replacements have the indicator facing the side so I may need to carry a small mirror to see the indicator.

Flue:

First, the thought of doing this was giving me cold sweats. I had read many posts about how to get to the flue tube. One person said remove 2 screws and slide the fridge out ... yeah, right!. One creative person said the top of the flue tube was next to the inside of a closet so he cut a hole in the closet and made an access door. Mine is behind the wall next to the front door. ... nah, I decided to go in through the screen on the vent. Seeing the flue is a real challenge. As Jim said, it is real cramped in there and DARK! I could not even see the top of the flue through the winding pipes. I finally took a small 3" LED flashlight tied to a string pointing downward and dropped it down between the tubes. There was the top of the flue, 2 feet down. The loop of the flue baffle hanger wire has one side that goes into a small hole on the top of the flue tube. The tool Jim used would have been ideal to grab it. I used a coathanger wire and "brute force and ignorance" to pull the hanger up.

I wish I had taken some pictures of the flue baffle when it was out. I may give another try at pictures since it is not all buttoned up yet. I was going to wait until I put in a new regulator and while I am at it, new pigtails since the old ones are getting stiff. Why tempt fate!

Oh, yeah, cleaning the flue. I had some springy wire that I think came from an old aircraft longwire antenna. I bent a small loop in the end around some paper towel with alcohol on it and pushed it up the flue from the bottom. An after thought would be to put a cleaning rag on an electrician's snake and drop it down from the top. Dometic does give a part number for a flue brush, Dometic Part No. 0151404001, but a Google search didn't turn up anyplace to get one.

John, the link you gave was the one I wanted to find, thanks. Here is the link again:
http://www.sunlineclub.com/forums/f7...cks-10981.html That manometer it a fancy one.

My stove top is different with the burner attached to the top cover. When you lift the top, just the jet and piping to the valve is underneath.

**JohnB** · 09-03-2013, 10:59 AM

Quote:

Originally Posted by jim44646

I sure like your propane cover. Wish they still made those. I took my flue baffle out a while back.
it's so cramped in there it would be hard to get a photo. I used a mechanics tool retriever to grab hold of the el shaped wire and pulled it straight up. After all that it wasn't that bad. The reason I pulled it was I had the refrig vent cover off installing a couple computer fans on the wire mesh for coil cooling.
AmPro T19602 3-in-1 Retriever Claw and Lighted Magnetic Pick-Up Tool | ToolBarn.com

Jim,

I have several of those gripper tools... but WOW, how in the world did you get in there?

Did you pull the roof vent off and come down from the top or figure out how to go up from the side of the camper through the vent panel access?

The LP covers, they are hard to find. Sunline called them a "Delux" cover. Seaching around a few years ago, new they where insanely expensive, like $300 worth... That was only 1 source. Then on the RV surplus market I have heard they went for under $50...??? I thought Trailblazer found a few of them. Do not know for sure they are not made any more, but have not found them for sale either. And that was a severla years ago seaching.

**JohnB** · 09-03-2013, 11:06 AM

Quote:

Originally Posted by Gene

John,

Seems there are only 3 choices for auto changeover 2-stage regulators since I can no longer get the Marshall like my current one with the window on top to see the red band.
* Marshall Excelsior MEGR-9984P (not the same company as Marshall Gas)
* Cavagna which is also sold as Mr. Heater. Several sites show a glass dome version where you can see the red from the top. Cavagna stopped making that version before 2009.
*Camco 59005 - the link John posted above

Gene, I wonder what any brand new campers are now using since Marshall Brass has gone under? I'll have to start looking now.

We have several folks now with SOB brand new campers and I'm sure they must have a switch over regulator. Curious what brand they are installing?

I looked up the other 2 brands you talked about, have not seen them in use yet. That said I have seen another one, I'll have to hunt it up. Or it might be a 2 stage regulator, just not an auto switch over.

Thanks for the leads. Some day I'm sure I will need a replacement.

John

Gene · 09-03-2013, 01:22 PM

I ordered the Camco from Amazon last night, "free" shipping.

I also came accross one by Fairview Fittings, GR-9984.
Two Stage Automatic Changeover :: Rv :: Industries :: Fairview Fittings

It seems to be a Marshall Excelsior MEGR-9984. I think Fairview makes (imports) them.

jim44646 · 09-03-2013, 03:53 PM

Quote:

Originally Posted by JohnB

Jim,

I have several of those gripper tools... but WOW, how in the world did you get in there?

Did you pull the roof vent off and come down from the top or figure out how to go up from the side of the camper through the vent panel access?

The LP covers, they are hard to find. Sunline called them a "Delux" cover. Seaching around a few years ago, new they where insanely expensive, like $300 worth... That was only 1 source. Then on the RV surplus market I have heard they went for under $50...??? I thought Trailblazer found a few of them. Do not know for sure they are not made any more, but have not found them for sale either. And that was a severla years ago seaching.

I took of my refrig roof vent. I was in the process of doing a cooling mod when I decided to check mine. Since I had the screen cut I figured what the heck. I took a flash and looked in there. I tried reaching down but couldn't reach to well. That's when I came up with the gripper idea. Once removed I was suprised how little rust was on it And how small it is.
The mod I did was slip 2 computer fans,up flow, under the screen and fastened them with a couple screws through the screen. Ran wires down to an empty fuse in box. Put the vent cover back on. When I want them on I plug in the fuse.

**JohnB** · 09-03-2013, 08:12 PM

Quote:

Originally Posted by jim44646

The mod I did was slip 2 computer fans,up flow, under the screen and fastened them with a couple screws through the screen. Ran wires down to an empty fuse in box. Put the vent cover back on. When I want them on I plug in the fuse.

Thanks Jim, as I thought you came down from the top. Next time I'm inot the vent cover, I'll come up with a removable section.

The fridge fan, yes a very worth while mod, I used the Valterra one. It for sure makes a difference
REFRIGERATOR FANS

Here is the install, uses a Klixon thermal disk switch.
http://www.sunlineclub.com/forums/f6...fan-10679.html

Also for reasons not yet figured out, I have tripped the fuse now 3 times. I added this so the wire would not turn into the fuse. Started with 1 amp, took that out, then up to 3 amp. That lasted a year or more and now took 2 of them out. So I up'ed to a 5 amp.

The only thing that make sense is moisture in the armature. This thing draws milli-amps when it is running. Have not yet tracked down the root cause.

Thanks

John

**JohnB** · 09-03-2013, 08:13 PM

Quote:

Originally Posted by Gene

I ordered the Camco from Amazon last night, "free" shipping.

Let us know how it looks/works once you get it.

bunjin · 09-03-2013, 08:40 PM

John,

Are you using time delay fuses or just said amp fuses. If time delay, how high a allowable amp spike on the fuse?

jim44646 · 09-03-2013, 08:49 PM

Camco vent cover ?is what I'm using. It dropped right in. for boondockers you can get it with built in fans and solid cells.
I get it duh. I was thinking vent not regulateor

**JohnB** · 09-04-2013, 05:25 AM

Quote:

Originally Posted by bunjin

John,

Are you using time delay fuses or just said amp fuses. If time delay, how high a allowable amp spike on the fuse?

At the moment just quick blow as the normal unit from Valterra had nothing. Well other then the very fine thin wire it has hooking it up. Wire does become a fuse pending the overload.... I was trying to be proactive adding a fuse to such tiny wire on a 15-amp supply.

I had thought about the need of a time delay fuse, and at this point will try some. A 1 or 2 amp time delay fuse may do it. This thing only draws ~ 250 milliamps and at worst 300 milliamps (confirmed by amp meter when boondocking) and would of thought 3 amp (12x larger) and now 5 amp (20x larger) would of handled what little inrush current spike this fan has. After it tripped a 5 amp quick blow I came to the conclusion, h'mm have to dig deeper on this one....

I may have to change to a small glass fuse as I do not recall ever seeing time delay in the automotive blade type fuses. Unless someone else knows. I made a cheap holder out of push on terminals. I have not been able to find them even on the Bussman site. But again never looked for one either. Generally in the auto fuses, they are most times after instant overload protection, short circuit protection and may be why I can’t find them.
Blade-Type Fuses

Thanks for the help to get my thought process going.

John