Refrigerator Performance and Maintenance

[StrongJava]

Hello!

We have been in our 2008 Bighorn 3670RL full-time now for about 10 days. In South Texas with hot days, we noticed the fridge seemed warm. I placed a freezer thermometer in and noticed we were hitting temps near 50 in the fridge (A Dometic DM2862). So I started Googling.

1) I removed the outside vent covers and noticed the increased air flow helped. I cleaned the inside compartments and noticed the fan was not running. Turns out my neighbor had a new fan assembly still in the box (he also has a Bighorn) and I installed that this past Wednesday. I notice that it never turns off, even during the coolest part of the day early morning. After putting that in I closed up the vents. Everything seemed to be running better and the fridge temps were closer to 40 degrees, and I was even able to lower the cold setting to 3-4 instead of 5. But, that only lasted for a day or two. Yesterday, we noticed the temp had crept back up towards 50. Exacerbated problem by getting groceries.

2) We've also read to keep food away from the sides of the fridge which we try to do as much as possible.

3) The freezer (even after 10 days) already has a good layer of frost built up on the back wall. I've read others say they only have to defrost a couple of times a year. Does it seem odd that we'd already have heavy frost in the freezer? Am I correct in assuming that is also hurting the performance?

What other maintenance steps can I do to keep the temp down?

Thanks.

Tim

 

[rxbristol]

Of all the things I've done to make the fridge more efficient (interior fan, making sure the baffle is correctly cut, etc.) two items help the most. One, due to the long recovery time, keep the fridge closed as much as possible. Second, see this post about an exterior fan: //heartlandowners.org/showthread.php/53276-How-I-Get-My-Dometic-to-Cool-in-100-Degrees

 

[danemayer]

Excessive frost buildup is caused by warm moist air. Maybe that's just the way it goes in South Texas, but it may be an indication you may have air leaks; perhaps a seal that's not laying flat, or that's loose. Try trapping a dollar bill in the door at various places and pulling it out to see if there's drag. If there's no drag, you have air leaks.

 

[StrongJava]

Thanks Rex. When I had been Googling, your post was one of those that had pointed me to looking for an exterior fan. However, mine is placed down between the upper and lower openings, and I don't have the baffles I've seen called for in drawings others have posted or the fan installation instructions. In particular, I am thinking a baffle is needed on top to direct the warmer air being pushed by the fan out the vent opening. Today, at least some of the air is likely being pushed on top of the freezer compartment.

I suppose I could move the fan up to the top of the compartment and pull the heat directly off the heat exchanger as you've done. I need to get material for create a baffle too.

I hesitate to install a fan inside the refrigerator primarily because I don't want to give up the space and, while I've heard it can positively impact performance some, the exterior fan is said to provide the biggest boost. Has that been your experience?

Thanks.

Tim

p.s., Are you in San Antonio?

- - - Updated - - -

Thanks Dan. I'll test the the doors this morning.

Tim

 

[StrongJava]

Because this is a high class joint here, I used a $50 bill to do the tests. And yes, I found too many spots where I feel the drag was not sufficient.

So, I guess that should be my next step. I'll looking replacing the seal, but do you know of any lubricant or cleaning that will improve the seal?

Tim

 

[danemayer]

Regarding seals, Dometic says:

If a gasket is not sealing properly, warm the gasket material with a hair dryer. Then close the door and the magnetic strip should pull the gasket to the metal frame. Leave door closed until the material has cooled. Then recheck for a positive seal. If a positive seal cannot be achieved, replace the door gasket.

 

[farside291]

Is it true that these refrigerators cool better on DC?

 

[jmgratz]

You can find a very small fan designed to circulate the air inside the refrigerator. Place it in the bottom to circulate the cool air to the top of the fridge. Also if the freezer is cold and the fridge is not then check the thermister on the fins. Moving it up makes it cooler and down warmer. (I think that is right)

 

[danemayer]

Is it true that these refrigerators cool better on DC?

Both the electric heat and gas heat should work about the same. I think gas performance can decline as altitude increases. If one or the other works significantly better, there's likely a problem with the poorer performing side.

 

[wdk450]

Thanks Rex. When I had been Googling, your post was one of those that had pointed me to looking for an exterior fan. However, mine is placed down between the upper and lower openings, and I don't have the baffles I've seen called for in drawings others have posted or the fan installation instructions. In particular, I am thinking a baffle is needed on top to direct the warmer air being pushed by the fan out the vent opening. Today, at least some of the air is likely being pushed on top of the freezer compartment.

I suppose I could move the fan up to the top of the compartment and pull the heat directly off the heat exchanger as you've done. I need to get material for create a baffle too.

I hesitate to install a fan inside the refrigerator primarily because I don't want to give up the space and, while I've heard it can positively impact performance some, the exterior fan is said to provide the biggest boost. Has that been your experience?

Thanks.

Tim

p.s., Are you in San Antonio?

- - - Updated - - -

Thanks Dan. I'll test the the doors this morning.

Tim

Check some of the cooling fans here: http://rvcoolingunit.com/Cooling-Performance-Enhancing-Items-C320215.aspx?sid=298 Very little affect of losing food space. You hook them to power from your interior light switch and the grounded metal inside the box. Maybe even phone the company for advice. Also think about adding insulation all around and above the refrigerator box to minimize dead air spaces.

It has been very hot here the past few days, and I am thinking about some way to shade the kitchen slide with the refrigerator in it. But I am moving back to the high Sierra today. 10 degrees cooler there.

Someday I want to move the outside blower fans to the inside of the top vent blowing out, causing an upward air draft up through the refrigerator heat exchange systems.

 

[farside291]

Thanks, I wasn't sure. Someone told me that along time ago.

 

[rxbristol]

You can find a very small fan designed to circulate the air inside the refrigerator. Place it in the bottom to circulate the cool air to the top of the fridge. Also if the freezer is cold and the fridge is not then check the thermister on the fins. Moving it up makes it cooler and down warmer. (I think that is right)

Jim mentions a good point about the thermistor being in the correct location.

 

[Lou_and_Bette]

Another thing to check is the drain tube where it exits the rig. There should be a plug there. If it is missing, hot, moist air can be getting into the fridge interior. Simple fix if it is missing, put small bend in tube using rubber band to hold in place and fill bend with water...essentially you are making a P-trap to keep hot air out.

 

[rxbristol]

Another thing to check is the drain tube where it exits the rig. There should be a plug there. If it is missing, hot, moist air can be getting into the fridge interior. Simple fix if it is missing, put small bend in tube using rubber band to hold in place and fill bend with water...essentially you are making a P-trap to keep hot air out.

Neat idea!

 

[avvidclif]

Hello!

We have been in our 2008 Bighorn 3670RL full-time now for about 10 days. In South Texas with hot days, we noticed the fridge seemed warm. I placed a freezer thermometer in and noticed we were hitting temps near 50 in the fridge (A Dometic DM2862). So I started Googling.

1) I removed the outside vent covers and noticed the increased air flow helped. I cleaned the inside compartments and noticed the fan was not running. Turns out my neighbor had a new fan assembly still in the box (he also has a Bighorn) and I installed that this past Wednesday. I notice that it never turns off, even during the coolest part of the day early morning. After putting that in I closed up the vents. Everything seemed to be running better and the fridge temps were closer to 40 degrees, and I was even able to lower the cold setting to 3-4 instead of 5. But, that only lasted for a day or two. Yesterday, we noticed the temp had crept back up towards 50. Exacerbated problem by getting groceries.

2) We've also read to keep food away from the sides of the fridge which we try to do as much as possible.

3) The freezer (even after 10 days) already has a good layer of frost built up on the back wall. I've read others say they only have to defrost a couple of times a year. Does it seem odd that we'd already have heavy frost in the freezer? Am I correct in assuming that is also hurting the performance?

What other maintenance steps can I do to keep the temp down?

Thanks.

Tim

I had a trailer with the same fridge. It did exactly the same thing. I went round and round with Dometic while in warranty. They only guarantee the temp specs at 90 or 95 deg (I don't remember which) outside temperature. Over that and it's whatever. Well guess what in Texas summertime that's the overnite temps at times. I never did get it to cool properly. The dealer tried everything, fans, ducting, etc. The previous fridge and the one after that piece of junk also dometic had the regular thermostat, not the, slide the thermistor up and down garbage. They both worked fine. Dometic messed up with that particular setup IMHO.

 

[StrongJava]

Thanks to all for the replies and conversation.

I did try the hair dryer trick around the freezer but not real positive impact. I'll probably try again on the fridge part today. As I have found the manual, I'll give that a read too.

Hey Bill, I was having the same thought as you about wanting to get to higher elevation Unfortunately, in Texas, not really an option! As soon as we get the house sold, we're planning to head to other parts, hopefully cooler parts. I'll look in the interior fans, but since I don't really plan to be in these hot of parts long-term, I may try to hold off on that mod. I guess you believe moving the exterior fan to the top of the box will be better? It seems worth a try and I can do that while I'm here.

My rig does seem to have insulation around the box, but who knows how well it was installed. There is a gap on the very top which I thought about filling, but then wondered if it was like that on purpose (condensation? Air circulation?).

I'll also check the thermistor location.

And, the tube, which I already suspect a problem with. My neighbor was told by an RV repair guy that the tube is supposed to run out the back of the ridge and then out of the bottom vent cover. Does this sound right? I suspect my tube is broken off and the proper positioning is not clear to me. I have more research to do with that.

Tim

 

[danemayer]

And, the tube, which I already suspect a problem with. My neighbor was told by an RV repair guy that the tube is supposed to run out the back of the ridge and then out of the bottom vent cover. Does this sound right? I suspect my tube is broken off and the proper positioning is not clear to me. I have more research to do with that.

Tim

The tube is a drain, so it's a good idea to have it draining outside. The cap on the end fits loosely to allow water to drip out without letting much air in.

 

[rxbristol]

My tube goes to a small drain container behind the fridge, not outside the vent cover.

 

[StrongJava]

I just looked at the thermister. It was not on the fins, rather it was laying in the little tray on the shelf. The mounting bracket is there, so I will try to remount it on the actual fins.

 

[wdk450]

Actually, that thermistor being disconnected from the fins would make the cooling unit run full out, in my opinion. The warmer the thermistor, the more the cooling unit runs.
Yesterday I moved from a site with Western exposure for the refrigerator slide to one (4500 feet higher elevation) with an Eastern exposure for the refrigerator. Although the outside temperatures here still got to near 100 degrees (it was 106 in Sacramento), my refrig and freezer kept very cool. BTW, I found small, battery operated digital temperature gauges on E-Bay for less than $3 each. I got one for each side of the refrig. The only drawback is that they are only available in degrees centigrade, but I just found a conversion chart on the internet and posted snips of it next to them.
The outside airflow not bypassing the heat exchange tubing is VERY important. Next, expensive, step if all else fails is to get a new Amish built, redesigned cooling unit from RVCooling Unit Warehouse (the same place with the fans). These use stainless steel tubing in areas subject to corrosion failures, and have tweaked the ammonia/chemicals mixture for better cooling and long life. They have also improved the freezer section for colder freezer temperatures. Supposedly the Amish Dairymen wanted colder temperatures to hard freeze the ice cream they produce.
I try to keep a couple of blue ice packs in the freezer to move to the refrigerator when the temperatures there are getting a little high.