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Old 08-18-2019, 06:44 AM   #1
bobnelms
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More Dometic Refrigerator Questions

Hi all,

Our freezer temps are usually 15 deg F, but even with nothing in the refrigerator I can't get the temps lower than 45 F.

I'd like to check the resistance of the thermistor, but I don't know which wire is the thermistor. I've attached a photo in hope that someone can ID the correct wire.

I also took off the upper vent from the outside of the RV, and noticed a piece of plywood that covers a lot of the opening. Is this piece of plywood supposed to be there??

Thanks ahead of time.
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Old 08-18-2019, 06:54 AM   #2
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That piece of wood is supposed to be there.

Since your fridge is on a slide, You should have some fans that run when the upper cooling unit reaches a certain temp, are you hearing them? At the right end ( in first pic) is the thermalswotch. jumper it to make sure the fans work, then if they do, see if the fans come on with the refer turned on. I think the set temp for that switch is like 120 degrees, You can use a heat gun to see if you can get the switch to operate. If it doesn't then I would start with that.

The thermistor plugs into the control board that is behind that cover. Should be marked. If not then its the two conductor, WHITE insulation wire. You can unplug it and then start the fridge and it will force the cooling unit into MAX COOL mode to rule it out.
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Old 08-18-2019, 07:06 AM   #3
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Chuckster57, this is great information. A followup question... you say that the thermistor plugs into the control board that is behind that panel -- do you mean behind the wooden panel in photo#1? If so, how to I get out that panel? It seems it extends a long way down into the rear of the refrig. Is it glued? Thanks so much..
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Old 08-18-2019, 07:09 AM   #4
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Im sorry, the control board is behind that black cover in the second picture. You should have two tabs on each side that you use a small flathead screwdriver to pop loose. The screw on the top holds the control board in place.
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Old 08-18-2019, 09:00 AM   #5
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I would remove that wood panel first even if you only cut the part out the size of opening.The thermo switch also called a snap switch should be hooked up to the hot lead on the second picture.Usually red and possibly have a 2 amp fuse in the line.You really need to remove the wood there is not enough air flow.I have our fridge set on the controler in side set midway and it is reading 35 lower and - 6 in freezer.I have 1 fan in fridge and 3 behind vents.1 lower 2 upper.Also pack some kind of insulation above the fridge and down the sides from the rear to remove dead spaces. If snap switch is bad you can get them on ebay 5 for like $8.00. Just search snap switches. Or just jump wires until you get a new one.
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Old 08-18-2019, 09:45 AM   #6
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DO NOT remove any of that wood! It is critical for proper air flow.
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Old 08-18-2019, 03:15 PM   #7
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Vent Blocked

Chuckster I hate to disagree he said that it was in a slide.The vent is more than half way blocked off. If it was not in a slide and had a roof vent maybe so.He can do as he pleases but he has no amount of open vent.Heat rises and does not like to turn corners unless forced with a fan.That is almost a 90 degree turn. I doubt anyone has seen a vent blocked off that amount.He has nothing to lose if it does not improve!!!!!!
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Old 08-18-2019, 03:22 PM   #8
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Quote:
Originally Posted by retiredusps69 View Post
Chuckster I hate to disagree he said that it was in a slide.The vent is more than half way blocked off. If it was not in a slide and had a roof vent maybe so.He can do as he pleases but he has no amount of open vent.Heat rises and does not like to turn corners unless forced with a fan.That is almost a 90 degree turn. I doubt anyone has seen a vent blocked off that amount.He has nothing to lose if it does not improve!!!!!!


Every fridge I have seen in a slide will have that board and fans located below the upper set of fins to help with air flow. Look at my signature, and you’ll find I’ve seen plenty of refers in slides and I might know what I am talking about. If you can locate installation guides from Dometic and Norcold, you will find that it is required and I have even ADDED more to some units.
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Old 08-18-2019, 04:09 PM   #9
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Yes, i suspect without the wood divertor, you would lose your airflow before it had a chance to flow thru the finned portion.
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Old 08-18-2019, 04:54 PM   #10
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Yes the baffle is from the outside wall to the edge of the coil forcing the air thru the upper coils. NOT BLOCKING THE VENT.Check out any after market site for baffles and fans. Also check the manufacters site for the install manual the baffle does not block the vents.
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Old 08-18-2019, 06:17 PM   #11
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Quote:
Originally Posted by retiredusps69 View Post
Yes the baffle is from the outside wall to the edge of the coil forcing the air thru the upper coils. NOT BLOCKING THE VENT.Check out any after market site for baffles and fans. Also check the manufacters site for the install manual the baffle does not block the vents.
It's not blocking the vent. There is a large opening at the back of the picture. It is put together as it is designed. If you take the time to look at the manuals you will all is correct.

Not sure how many RV fridges you've fixed in your lifetime, but as far ad knowing what they are talking about and having real world experience in working on these, my money is on Chuck and his suggestions to fix them.

If your fix was followed and it didnt work, what would be your next fix? Put the baffles back? SMH.
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Old 08-18-2019, 07:02 PM   #12
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This is from the Norcold install manual for our 1210 fridge. The red arrow points to the baffle installed in a slide installation .
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Old 08-18-2019, 07:26 PM   #13
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And this is a photo from the same manual for the Norcold that shows the baffle installed in an enclosure that isn't as deep as the previous photo. The baffle is item #26 in the photo.
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Old 08-19-2019, 04:56 AM   #14
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Chuckster57, first of all I will NOT remove the wooden baffle. I never like to tamper with original design unless I thoroughly understand what I'm doing. As you and others have said, that wooden baffle is obviously present to assure flow past those upper fins.

Another question: inside the refrig, the thermistor is placed in a "clamp" that can be positioned up or down on the fins inside the refrig. If it's place high, it's supposed to get colder. If it's placed low, it's supposed to get warmer.

WHY? Is it because hot air rises, and so it ought to be hotter at the top of the refrig?

Another question: Is it the fins themselves that cool-off the inside of the refrig? If so, how do the fins get cold? Can you provide a schematic of a typical dometic refrig?

Thanks so much.
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Old 08-20-2019, 01:16 PM   #15
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I was questioning our fridge as well, I have attached an image of our install which shows the plywood as yours does, however ours has a piece of metal that is curved over top as well. Not sure if it supposed to be there or not because I don't see one on your top vent.
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Old 08-20-2019, 03:41 PM   #16
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Quote:
Originally Posted by bobnelms View Post
inside the refrig, the thermistor is placed in a "clamp" that can be positioned up or down on the fins inside the refrig. If it's place high, it's supposed to get colder. If it's placed low, it's supposed to get warmer.

WHY? Is it because hot air rises, and so it ought to be hotter at the top of the refrig?
Yes. The higher the sensor is, the more active cooling the fridge has to exert to keep it happy.
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Old 08-20-2019, 04:07 PM   #17
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Originally Posted by bobnelms View Post
Chuckster57, first of all I will NOT remove the wooden baffle. I never like to tamper with original design unless I thoroughly understand what I'm doing. As you and others have said, that wooden baffle is obviously present to assure flow past those upper fins.

Another question: inside the refrig, the thermistor is placed in a "clamp" that can be positioned up or down on the fins inside the refrig. If it's place high, it's supposed to get colder. If it's placed low, it's supposed to get warmer.

WHY? Is it because hot air rises, and so it ought to be hotter at the top of the refrig?

Another question: Is it the fins themselves that cool-off the inside of the refrig? If so, how do the fins get cold? Can you provide a schematic of a typical dometic refrig?

Thanks so much.
All good questions. Funny thing is the manual for my fridge doesn't even mention the thermister. It says it has a fixed setpoint. The thermister is not physically attached to the cooling plates it's just suspended loosely in the dead air space between the fin and the wall. I've read that it only gives you a few degrees +- of the fixed setpoint.

The cooling fin assembly is just fins attached to a plate which is then attached to the cooling unit. You'll notice the freezer doesn't have fins but if you feel the back wall it's cold. The fridge side works the same way but it had fins on a plate attached to the back of the fridge.
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Old 08-20-2019, 05:11 PM   #18
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Funny how I stumbled on this thread. I was just going to start a search.

We are a couple days into a 10 day trip and my fridge isn't as cold as usual. It's working but cools like on a low setting. Some things in the freezer are on the soft side and the lower section isn't as cold as usual.
I checked to make sure the thermistor in the fridge is in the upper position, and it is. I ran it on gas and 120...same results.

I'm thinking the thermistor... so my next step in the morning will be to unplug the thermistor and see if it gets cold.
Hope that's the problem. Like they say, it's always something.
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Old 08-20-2019, 06:06 PM   #19
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Originally Posted by gluck View Post
I was questioning our fridge as well, I have attached an image of our install which shows the plywood as yours does, however ours has a piece of metal that is curved over top as well. Not sure if it supposed to be there or not because I don't see one on your top vent.
Our Dometic fridge has the same black aluminum panel. Our fridge is in a slideout. Seems like a proper install. The factory had a fan below it so when it gets real hot ambient temp the black panel has the fan air deflected/moving over the fins on the tube. I went a year and half with that setup. This year I added the two fans at the top to push more hot air out of the top vent and that's improved the interior fridge/freezer to get colder when the sun is cooking on the camper all day.
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Old 08-20-2019, 06:43 PM   #20
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The basic premise as I understand it is this:

Cooling solution is “boiled” by either a heating element or a flame. As it travels down the coils, it “absorbs” heat from the interior by use of plates and fins. I think as it moves to the lower portion (fridge) it’s ability to absorb heat is diminished and that’s the reason for the fins- more surface area. There is a thermal mastic that is applied to the tubes of the cooling unit before it’s attached to the “cabinet” to help conduct heat.

Any number of reasons can cause issues with temps: poor air flow, blocked cooling unit passages, loss of cooling solution, bad door seals, etc. there are forms issued by refer maker that we fill out to help them determine why it isn’t cooling correctly. Most often when a fridge is in a slide and the freezer is okay and the fridge section is too warm, it’s either the fans or the door seal.

This is based solely on my experiences, it’s not the ONLY reason, but seems to be the most common.
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