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Old 07-23-2012, 11:56 AM   #1
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1972 Dometic RM 75a losing temperature

While successfully replacing my water heater, my fridge started losing temperature. First of all, we are experiencing record heat in Charlotte. And I am wondering if the unit is struggling with the heat? Yesterday, which was slightly cooler, showed a slight improvement (50 degrees fridge and barely frozen ice) as opposed to 60/melted ice in the days before.

Two questions:

Is there any hope to service and/or repair the unit?

In the events that I need to replace it (I've located 2 way Dometic replacements in the $1000 range). What is a good plan to remove the fridge? I have carpet in the trailer, and it looks like I may need to pull it up and out of the way.

Thanks.

John
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Old 07-23-2012, 12:28 PM   #2
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You stated that "while successfully replacing my water heater" you started having fridge problems. Do you think this is related? If you're running both the new water heater and the fridge on LP with an old regulator, it's possible that you're not maintaining the recommended gas pressure of 11 inches of water at the refrigerator and you were (or were closer) before putting in the new water heater.

Do you have the same behavior from the fridge on 120v and LP?
Do you have the fridge's controls set to the coldest temperature?
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Old 07-23-2012, 01:10 PM   #3
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DKB is correct. You have to determine if it is operating the same on 120v versus propane. Remember that in real high temperatures the fridge may not maintain a real cold temperature. I monitored my fridge temperature over a few days of hot temperatures. In the morning the fridge would start out at about 32 degrees then by 5:00 it might be into the high 40's. I would monitor the outside temperature and fridge temperature over time to get an idea of how the fridge temperature varies. If it really is too warm, there are some steps to take to keep it cool during the hottest part of the day- like installing a computer fan in the exterior heat transfer area to improve heat transfer performance or by adding ice to the fridge in the morning to maintain the temperature close to 32 degrees. A new fridge may not solve your problem.

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Old 07-23-2012, 01:28 PM   #4
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Of course do remember that your refrigerator is 40 years old and nothing lasts forever. They are fairly reliable but eventually it is time for a new one.
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Old 07-23-2012, 03:33 PM   #5
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Thank you all for the above replies. I have been running the fridge exclusively on 120v and the water heater on gas, so I think that they are not related. I do hope that it may be the excessive heat and humidity, both of which would affect heat transfer. We've been mid 90's for several weeks now, and that part of the trailer gets a dose of full sun at mid day.

I totally get the 40-year-old part, and I am work timing (full timing) most of the year, so the old girl is starting to show some were and tear from her new inhabitant.

I am going to recheck the cold settings, and set to coldest if it is not there already. I'll look into adding an auxiliary fan.
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Old 07-23-2012, 03:44 PM   #6
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Also check to make sure the vent is clear (both inlet and outlet) so that air flow across the heat exchanger is not restricted.

My 37-year-old refrigerator has managed in 100-degree days with little shade, though the fridge in my trailer is on the awning side so I'm sure that helps. On hot days when we're using the refrigerator actively (cooking for a pot luck, for example) I put some old water bottles in the freezer until they're frozen solid, then move them to the refrigerator compartment and move the somewhat-thawed ones back to the freezer. 1 swap midday is all that's usually required, but at 100 deg it's required.

I don't have a fan in my refrigerator vent, but my particular trailer has a huge intake area under the trailer and the vent is clear of obstructions. I should stop talking about how mine works well, or it'll decide to stop and I've already planned my 4-figure updates for this year, axles not iceboxes!
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Old 08-13-2012, 06:41 AM   #7
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My fridge did recover good temp once the high heat and humidity subsided. And it was in fairly good shape for another week or two. But now it is dead. On the backside of the fridge, there is an enclosed box where the electrical supply and the coolant pipes run in and out of, and it was too hot to touch.

I am guessing that it is time to replace the unit. It seems that Dometic has an appropriately sized replacement. And I am willing to take on the expense ( I do live in my Airstream most of the year). I guess that I am most concerned about removing the old unit and installing the new one. My trailer has wall to wall carpet and I think that I may have to pull it up to get the unit out.

So I am now looking for any good advise on removal and installation. I guess the water heater was a good warmup for my next project.
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Old 08-13-2012, 05:25 PM   #8
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Is it true that I will need to disassemble the credenza and partition wall, and maybe even the pantry, in order to remove the old fridge?

Oh dear, I hope not.
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Old 08-13-2012, 07:02 PM   #9
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I just discovered the play-by-play for removing the RM75 in my 1972 Airstream Service Manual. Lots of disassembly, yes. But at least I have a clear road map.

It has been recommended that I try adding cooling fans. My question is will this work when I have absolutely no cooling going on right now? Nada.

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Old 08-13-2012, 07:33 PM   #10
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We did not have to remove the credenza or the pantry but you will have to remove a lot of screws that are in both of them. The partition wall in ours slid out twards the stove and we were able to get it out of the way to work the fridge out (we dont have carpet though). There will be just a few small spaces that will need to be filled with some type board along the side and top of the new fridge. I was also able to use the old front panels on the new fridge ( with one seam in the refer door). On ours the gas line was installed too far in on the trailer by 1/2 an inch so we made a notch it the new refer pan to clear it.
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Old 08-14-2012, 05:48 PM   #11
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Alrighty then, after much consternation I ordered the Dometic New Generation RM3762. The other option was the DM2652. Camping World had the RM3762 on sale for $999.99 which was better than the best price I could find for the DM2752. As much as I would like preserve original look and function in my Airstream, I decided that the newer technology and features of the New Generation are too good to pass up. Plus I get an extra cubic foot to boot.

Hey Mike (memgrove2000) What model did you use for a replacement?

I will keep ya'll posted. Meanwhile, I am eating out more often than not.
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Old 08-14-2012, 07:27 PM   #12
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I am pretty sure it is the RM2820 which was the direct replacement off the Dometic chart. The trailer is 2 miles down the road at the farm house or I would run out an take a picture for you.

It looks good in there. I used the old refer panel in the new freezer door (Cut with razor knife). Then took the rest of the Refer door skin on the top of the new refer door and then filled the lower part with the old freezer panel. Dometic sent a trim piece to hold the top or bottom of the new fridge door panel. I used it in between the top and bottom refer door panels. When done carefully the wood grain will even line up and look factory.
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