Dometic Frig Periodic Maintenance

[benny@waskomtexas.com]

I posted something similar to this before, but I need some specific information if anyone has it. I don't need to know how they work, I know that. The manual is too general, I have read it. Someone out there surly has worked on these units. Many people read these posts I need some help on this from someone that has actually got their hands dirty doing the job.

We have a 1997 Dodge Roadtrek 190 with a Dometic RM2310 Refrigerator. This was running on gas. It has worked just fine until the lat two trips, to Flagstaff in May and to Colorado in July. On the July trip it was worse so I feel that something is going wrong. We filled the LP gas tank before we left for Colorado. We were gone for a month. When we returned home the tank was just about to touch the "Red" line. We took some temp readings while we were on the trip, but I have forgot. The freezer was still freezing food but the bottom was in the 45 degree range. We had it set on max.

This is Sunday afternoon about 5:30, I turned it to Electric, set it on 6 and put a thermometer on the bottom shelf. I will see what will do on elec. Tomorrow I will get some good readings running on elec, then I can compare them with gas operation.

Concerning the gas operation, I figured that it was full of carbon. However. I removed the cover, part #46, from the burner housing, part #33. Yes it is hard to remove, and it would help, as someone said, if I was 2" tall. I could just barely see the burner, but after I got a mirror and a flashlight I could see it very well. There is NO carbon build up on the burner, assembly #32 at all. It looks brand new. The thermocouple, part #3, was clean also. If there was any carbon on it I could not see it. This surprised me also, because we have had a few times when it did not light on the first of second try. The flame was blue and about 1/2" tall so I see no reason to remove the burner jet, part #38. If it was clogged restricting the gas flow the LP gas to air ratio would not allow the blue flame that I have.

I could not see part #68, heater, because it is inside of the flue. I see that the flap, part #102, can be removed. So if I remove the flap can I see the heater and see if it has any carbon build-up ? Also it seems to be removed by binding the lip or unsnapping it. Tell me about this, have you personally opened it up ?

[wolfe10]

For those who don't have a manual for your. go to this site to find Dometic (and Norcold) owners manuals: http://www.gasrefrigeration.net/dometic_manuals.htm

This may be the one for your model: http://gasrefrigeration.net/dom_techdata/2300_2800OP.PDF

Page 11 is very specific about what needs to be done.

But, on all absorption refrigerators, the following needs to be done annually or when problems occur while on propane:

Remove and clean the propane jet. Even a small spec of dirt can clog it. Use alcohol to clean it. Blow through it backwards. Do NOT use anything hard as it may change the opening size.

Remove the burner tube and clean. Rust falls in it, dirt collects in it and insects seem to love to build nests in it. Do NOT short cut and try to blow it out with compressed air-- insect nests and dirt that has gotten wet will not always blow out.

Remove and clean the igniter and on some models the separate thermocouple. Clean any carbon or dirt off them. When installing, set them per instructions with proper gap and centered over the flame.

Check all grounds and wire connections for tightness (back of refrigerator where you are working).

For all propane appliances, check regulator pressure. For instructions on building a manometer: http://www.rverscorner.com/articles/manometr.html

Brett Wolfe

[benny@waskomtexas.com]

I find nothing listed as a "Burner Tube" I have to assume that you are referring to part of the burner assembly #32 that has the vertical slits where the gas and air exit to burn.

This morning the frig part was 55 degrees and the freezer was 3 degrees. I did not have time to check, but surly there is some restriction between the two. I am guessing that the freezer air has to migrate down to the frig part and that is not happening. Or the other reason is that the seal is leaking at the bottom.

[wolfe10]

Yes, the tube with slits in the top is the burner tube that needs to have rust, dirt and insect nests removed from it.

And the single cooling unit goes through the freezer FIRST, THEN the refrigerator. The thermistor that turns it on/off is in the refrigerator-- look on the back metal fins.

If you do not have adequate cooling after the burner area tune-up, check the door seals. Close the door on a dollar bill (OK, it is an RV, so a $20 works better). There should be smooth resistance all the way around the doors.

Also, check the condensate drain to make sure the restriction in the drain end is in place. If it is not, hot air can easily enter the refrigerator (not air rises).

Also check the back of the cooling unit for any restriction to air flow such as bird or animal nests in/near the top vent.

As with any refrigerator that does not perform to specs, read the refrigerator manufacturers installation manual (particularly in terms of side and top clearance) and VERIFY that yours is properly installed.

Brett Wolfe

[benny@waskomtexas.com]

It's hot outside so I am not going to spend much time out there today. In the morning while it is cool I will do some of the check that you suggest. Also I just looked inside the refrigerator and there was a thin layer of ice on the very back of the cooling flange, part #4. At this point I think that as you suggest I have a air leak that is causing the problem, but I will check all of the other things that you have suggested.

[benny@waskomtexas.com]

I tried the $1.00 bill, it had a firm pull, I use a credit card on our house frig, so the seal is good. Did not find a condensate drain in the frig compartment. I checked the temps this morning at 6:00AM. It is 73 outside, 3 in the freezer, 45 in the frig and inside the outside inspection door is of course warm, because of the components, but the temp is about 80. There is ice on the cooling flange. The frig is empty that might make a difference.

I am going to switch to gas operation today to see if I get the same readings.

[MattSmith]

Reading these commentaries with great interest as I'm having a similar problem with the Norcold Model 6162 in our 1994 Winnebago Adventurer.

On electric operation, the best it will do is about 47 deg. F in the fridge, 16 or so in the freezer, even at outdoor temps in the 70's (in "temperate" Connecticut) with an electric fan blowing into the exterior access hatch. Gas operation seems no better, no worse. Nice blue flame, lights and runs OK. I can see daylight from the coach roof thru the ventilation area between the back of the refrig unit and the outsided wall of the coach; nothing like bird or mouse nest etc. that I can see with mirror. There is a condensation drain and receptacle , both bone dry, end of hose apparently pinched at manufacture to prevent back leakage of air. I took out the burner and its heat shield and was able to "bump" the flue up and down about a half inch, loosening up a lot of rust, which I vacuumed away. The "dollar bill" caper show both door gaskets OK.

In this installation it looks physically impossible to do much more without detaching the refrig unit from the coach for acces to the back side, which I'm loath to do as you can guess. - - Not sure about putting a new unit in a coach this old, but it's doing what we ask it to (mostly!)

All suggestions welcome! - - Matt S.

[wolfe10]

Matt,

While it could certainly be a bad cooling unit, below are some things that will insure maximum performance from your refrigerator (in addition to the "burner area tune-up"discussed above). Cooling units can fail by leaking with symptoms of ammonia smell and/or yellow powder or by the build-up of restrictions in the cooling tubes. Both types of failure call for a new refrigerator OR new/rebuilt cooling unit.

Do you have a thermostat and is it dialed all the way cold?

Have you moved your thermistor all the way up on the outside refrigerator fin?

And the outside auxiliary fans work a lot better if at the top of the cooling unit exhausting UP. You may be able to reach that upper area by removing the roof vent.

While there, make sure there is not an air gap at the top of the refrigerator that allows the hot air to collect rather than exhausting efficiently out the roof vent.

Brett Wolfe

[MattSmith]

OK, time for me to own up!

Your very first question about the thermostat made me actually look at it, which I hate to admit I had not done. It's up in the top right corner of the fridge, near the ceiling, where the light isn't very good (EXCUSE ALARM FLASHING!). Has settings numbered from 1 to 5, reading left to right. The left end of the scale is clearly labeled COLD. The right end of the scale, which I never looked at until just now, is labeled COLDEST. We had the thermostat at the extreme left end, with obvious results. It's now an hour later and the freezer is down to 10 and the fridge about 40 and dropping.

Many thanks for your help! This thing has received more TLC in the last three days than in the 2/3 of its life that we've owned it.

Cheers! - - Matt S.

[benny@waskomtexas.com]

Matt, Wolfe is coming up with some good suggestions. I have not taken the time to check some of the things that he suggests. I am moving slow, because I have a project going in the garage where I have built a sheet plastic room that I am air conditioning with the A/C out of the motor home. The temperature in the room is 68 degrees. The morning temperature in the motor home garage is about 74 mornings and 95 in the afternoon. We will not be using the MH until the end of September, guess where I am spending my time.

I am taking care of the MH some mornings if it is cool. I have a pretty long list of things to fix on the MH before the end of September, replace the A/C (done), clean and fix the two burner stove, replace the micro wave (done), Popping Noise Underneath (in shop nest week, Repaint Side Pouch, redo Interior Cabinet Finish, Remove Left Driver Arm Rest (done), Touchup paiint Back Window, install a Shelf Above Commode, add Windshield Fluid.

And of course the refrigerator. Matt, I am about at the same position as you, I do not want to have to remove the frig and it is very hard to work on it installed. I was just able to remove the cover that is over the burner, tight spot.

[benny@waskomtexas.com]

One thing that I am convinced is that the problem is not related to the LP gas Flame, because I am getting the same temperatures with electric operation.

Also this link is on the Yahoo forum concerning RV frigs:

http://www.rvmobile.com/tech/Trouble/Index.htm

One link shows how they work, good illustration.

http://www.rvmobile.com/tech/Trouble/cooldoc.htm

A number of years ago I did quite a bit of art work for an ad agency who had the Arkla Gas account, they sold Servel A/C units. They were an A/C system for homes and Business that worked the same way as the RV units. I knew that our units separated water and ammonia with heat. I just didn't know how the separation unit was made.

I have been told that if you operate the unit in un-level that some part of the heating unit gets too hot and small particles of metal or something form and clog up the system to the point that it will not work. I was also told that if the whole unit was taken out of the MH and turned upside down then it would work again. I don't know if these are true, a lot of crazy information can get out on the web.

I think that if we go thru the steps that Wolfe suggests we will find out what the problem is. Please stay in touch Matt and let's see if we can solve this problem.

[pkunk]

When I had a problem with my Dometic cooling on gas but working fine on electric it turned out to be a low flame height. I had already replaced the cooling unit that had failed, and had sub 0° in the freezer and 34° in the fridge on electric. Left on a trip with a good looking gas flame, so I assumed it was working. Fridge was up to 50° the first night & I had no clue what was wrong so we bought ice to preserve food. The fix was to clean the burner orfice. Here's the pics of before & after of the flame height.

[wolfe10]

Thanks, Paul.

Great pictures-- really shows what a difference doing the routine maintenance can make.

Brett Wolfe

[benny@waskomtexas.com]

(Have you moved your thermistor all the way up on the outside refrigerator fin?)

Wolfe, I don't know what this is. In the morning I am going to work on the MH. At that time I will go step by step in trying to find out what the problem is. I still have the thermostat set at 6 and the temperatures are "0" and 40 degrees. I am going to change it to "Max" this morning. Yesterday I looked at the Cooling Flange Part #4. There is a copper tube that comes into the frig compartment and attaches to the bottom of the cooling fins. This must be the thermostat, part #7.

Also yesterday I looked for any yellow stains or power and found none. I have the unit back on Electric operation. form what I read that is the "standard". However, the temperatures do not change between LP Gas and Electric. This indicates to me that the LP Gas flame is good and the problem is "on up the line".

[benny@waskomtexas.com]

I don't know what to think about the frig. I have it set on "Max", it is "0" in the freezer and 40 in the lower frig, this is on Electric. The outside temp was about 90 today and the MH set in the sun this afternoon, we had clouds this morning.

I put some strips of foam on the door seal, that did not help.

I did not see any yellow powder.

I still don't know what the "Have you moved your thermistor all the way up on the outside refrigerator fin?" is.

I am not sure how they vent the frig on a Roadtrek.

I don't see a "condensate drain", but will look for it.

[wolfe10]

I still don't know what the "Have you moved your thermistor all the way up on the outside refrigerator fin?" is.

I am not sure how they vent the frig on a Roadtrek.

I don't see a "condensate drain", but will look for it.

We are on the road right now and don't have access to specific information on your model.

It may be that the thermistor is not movable-- it is on most models. The thermistor is what senses temperature and along with the thermostat tells the unit to turn on/off.

And again, most models do have a condensate drain, but look in your literature to see if you have one.

And most definitely read the Installation instructions that came with your refrigerator VERY carefully. Do not ASSUME that it is correctly installed-- VERIFY.

And one simple test is to run it on propane. If the flame stays on all the time and temps are still not cool enough, you can rule out the thermostat and thermistor as the cause, as they are telling the unit to run 100% of the time. BUT, if it cycles on and off and is not cool enough, then you likely have a thermostat/thermistor issue.

If you are safe working with 120 VAC, you could run the same test on 120 VAC. Just CAREFULLY hook up a voltmeter to the two leads going to the electric element and see if it stays on (voltmeter reads 120 VAC) all the time or cycles.

Brett Wolfe