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Jim & Susan · 09-20-2013, 06:16 PM

So I finally found a solution....buy a new cooling unit. You can read about the earlier gymnastics over here if'n you can't get to sleep tonight: http://www.airforums.com/forums/f425...one-83301.html Simply got tired of wrastling with the dern thing. Sometimes it would cool, sometimes it wouldn't. Freezer always worked, fridge sometimes worked. Replaced the unit last Monday (last week, 11 days ago). Been running continuously since with no issues including an 800 mile trip camping last weekend. However, I'm still not convinced that the old cooling unit is actually bad. There are three basic reasons that I'll spell out with pictures shortly. Hang in there gang, be right back.

Jim

Jim & Susan · 09-20-2013, 06:30 PM

Reason One:
The cooling unit was not sealed on the back of the fridge.

Reason Two:
There was no insulation between the cooling unit and the body of the fridge (same as above, sorta).

Reason Three:
The interior wall may not have been seated properly against the cooling unit on the back of the fridge.

One at a time......

Jim

overlander63 · 09-20-2013, 06:47 PM

Jim, I hope your cooling unit does better than ours. Replacements would work for a couple of weeks, then the fridge would not cool, but the freezer would freeze. After a parade of 6-8 cooling units, I finally gave up and put in a new fridge.
May The Force be with you.

Jim & Susan · 09-20-2013, 07:05 PM

Quote:

Originally Posted by overlander63

Jim, I hope your cooling unit does better than ours. Replacements would work for a couple of weeks, then the fridge would not cool, but the freezer would freeze. After a parade of 6-8 cooling units, I finally gave up and put in a new fridge.
May The Force be with you.

Dang! Let's hope so! Read on.......

Jim

Jim & Susan · 09-20-2013, 07:09 PM

First a couple of pictures, then the explanation for Reason One above. Back view and front view of the actual cooling unit. Please excuse the unkempt nature of our back porch. Grandkids, plagues of locusts and roving band of relatives and friends have conspired against me.

Jim

Jim & Susan · 09-20-2013, 07:22 PM

This particular Dometic (model NDR 1063) was built in such a way that the cooling unit is simply bolted to the back of the fridge. The fridge itself has a "well", if you will, molded into the back of the fridge that the cooling units simply rests in. Unfortunately, I don't have a picture of the back of the fridge with the cooling unit removed--wasn't thinking that far ahead at the time.

The point of this is that the cooling unit is just bolted to the back of the fridge, IT WAS NOT SEALED IN ANY WAY. My reading of that is that the cool air created by the coils may have well been simply leaking out. It's not any harder than that. And how would you be able to tell? Any cool air seeping out around the back of the fridge would be undetectable because of all the heat generated back there.

When we installed the new unit, we sealed everything up with aluminum tape. More on sealing in a few minutes.

Jim

moparjohn · 09-20-2013, 07:35 PM

I too hope to restore an original fridge for my Tradewind. I am hoping you are fixing something like a Dometic M75? Where did you buy the new unit? Thanks John

Jim & Susan · 09-20-2013, 07:49 PM

More on sealing things up.....

That "well' that is mentioned above is a sort of beveled arrangement. The bevel is made in such a way that the two mate together. Bevel in one direction on the fridge, the other direction on the cooling unit. The two fit together, but not very tightly. It's almost impossible to see the bevel because of the black plastic around the edge of the cooling unit, but it's there. The folks that we bought this refurbed unit from included a can of spray foam insulation--the same stuff you can buy at HomeyD's or Lowes for use around the house to seal up, say, the gaps around the outside of your house at the hose bib connection against the siding. The idea here is that you run a bead of this spray foam at the bottom of that well and it expands to fill the gaps once the cooling unit is seated fully.

Jim

Jim & Susan · 09-20-2013, 08:13 PM

So, if my poor interpretive skills are making any sense at this point, we now have the cooling unit mated to the back of the fridge and PROPERLY SEALED. Something the factory neglected to do. Now about screws and this thing:

Jim & Susan · 09-20-2013, 08:28 PM

If you look inside the fridge (not the freezer) you'll see some fins similar to these. The purpose of these fins is to transfer the cold of the cooling unit coils to the inside of the fridge compartment via simple contact (which is one reason why these accursed things take so long to cool down). If they are not making good contact with the coils, the transfer won't be very efficient, right?

There are several screws inside the fridge that screw thru the fins and into a steel plate that the cooling coils are attached to. The idea here is that the screws pull the coils up tight against the fins (and logically, against the back of the cooling compartment of the fridge) to transfer cooling to the interior of the fridge area. Cold on coils = cold in the fridge. Same thing in the freezer, but more on that in a minute.

But wait, there's more!

doorgunner · 09-20-2013, 09:02 PM

the clocks ticking. I'm half way thru a pint of Ben & Jerry's

Jim & Susan · 09-20-2013, 09:03 PM

Dang, it's late and I have to go to work in the morning. I'll finish this up tomorrow. Including the joys of thermal mastic and the reason for screws in the freezer.

John, I bought the unit from these guys: RV Cooling Unit Warehouse

Nice folks.

Jim

doorgunner · 09-20-2013, 09:05 PM

you're Kidding me----- Ice cream finished
just when I get into something WORTH reading here ...the carpet gets jerked. oooohhhhhhno
will I sleep tonight,

Jim & Susan · 09-20-2013, 09:07 PM

Quote:

Originally Posted by doorgunner

the clocks ticking. I'm half way thru a pint of Ben & Jerry's

Sorry Gunner, I'm all tapped out for the evening. Remember how to cool beer in 'Nam using gasoline and compressed air? Same idea, in a twisted sorta way.

Jim

Jim & Susan · 09-21-2013, 07:08 PM

Hi Guys, I'm back. Sorry for the delay.

Thermal mastic. So when the new unit was shipped, the folks included a tube of "thermal mastic". Looks like a tube of Vulkem, same size, color, applies the same. When I called them to ask how to apply it, they simply said cover the coils in it, use the entire tube. Basically, the coils that touch the interior chamber of the fridge and freezer need to be slathered in this stuff. Look at picture number 2 in post five above..........

Jim & Susan · 09-21-2013, 07:16 PM

Notice how those coils have a (tiny, little bitty) bit of something that looks like calk clinging to them? That's the factory installed thermal mastic. Not enough to transfer any kind of cool air. This stuff is supposed to be there to aid in the transfer of cool to the inside of the fridge and freezer compartment. Doesn't work if it's not present.

Jim

Jim & Susan · 09-21-2013, 07:29 PM

Other miscellaneous ramblings. Look back at that same picture. #2 in post 5.

The top four of those coils rest against the back of the freezer chamber, the bottom TWO of those coils rest against the fridge chamber. Now, I'm not an engineer, but I do drink Natty Light on the weekends. Seems to me that one way to increase cooling capacity in the fridge is to increase the number of cooling devices (coils) in the fridge chamber. Again, I'm not an engineer, so there may be other reasons for this. I once read an Obewankanobi article on-line that described all of the exotic gasses mixed with the ammonia that make cooling happen. It's was a magical read, hydrogen falls down one tube, ammonia goes the other way. A small amount of a Noble Gas goes yet another direction and poof! A miracle occurs! Yer beer gets cold! Arrrrgggggg. It's just cold beer, why so complicated?

Jim

Jim & Susan · 09-21-2013, 07:41 PM

One other thing I forgot about. Make sure those screws that go thru the fins (and the matching ones in the freezer) are good and tight against the steel plate mentioned earlier. Once we installed the cooling unit and stood the fridge back up, we began to tighten down on the screws. You could hear the cooling unit being pulled up against the back of the fridge and freezer as we turned the screws. Don't hammer away at it, but "snug them up good."

Jim

Jim & Susan · 09-21-2013, 07:48 PM

OK Gunner, I'm done. Hope you had a reserve pint of Ben & Jerry's in the freezer.

Jim

cwf · 09-21-2013, 08:10 PM

Quote:

Originally Posted by Jim & Susan

OK Gunner, I'm done. Hope you had a reserve pint of Ben & Jerry's in the freezer.

Jim

Jim,
B&Js or not, I'll tip a keg for ya.

I think you are on to the trail,,, we use "thermal grease" on lots of our e-lectronical gizmommeters back when I worked for the "blue krew"... And it sucked that darn heat away and our systems performed "as designed".

I had "counterparts" who I followed on repair actions where the stuff was, ER, forgotten...oops. It killed new parts and caused lots of other inexplicable "errors" before failure.

It is important.

So, if someone has a marginal fridge, this would be one step in ensuring a "properly" setup system.

Do you know the name of the "goop" you used?