Dometic cooling capacity has decreased

[WesternHorizon]

1995 Class C with a RM2611

I bought it 5 years ago and the fridge has always worked well, but it did struggle last summer in 100 outside and 90 inside temps.

In the past few months I have used the RV very heavily. It seems like the cooling capacity has gone down.

Right now it is 88 outside and 85 inside, the fridge is on setting 5/5 (coldest), and it is holding just barely at 39F. Freezer is -6F. On propane.

It recovers overnight in 45F ambient temps, going down to maybe 32F with same setting.

AC power is a bit better but not much.

Wondering if the R717 (ammonia) could be a bit low? I very much doubt it has ever been touched in 24 years.

Thanks for any suggestions.

[WesternHorizon]

NRALIFR wrote:
Sure doesn’t sound like the latest cooling unit replacement fixed anything, but the performance improved noticeably after the LP regulator was replaced, which suggests the LP pressure was low. Did you ever measure it? Have you measured it since the replacement?

:):)

No, it looked like an original so I just replaced it

[NRALIFR]

Sure doesn’t sound like the latest cooling unit replacement fixed anything, but the performance improved noticeably after the LP regulator was replaced, which suggests the LP pressure was low. Did you ever measure it? Have you measured it since the replacement?

:):)

[WesternHorizon]

If you ask a question and I don't respond, it's because the answer or topic is in previous posts. Thank you.

[ajriding]

So, you replaced it and are you happy?

I was going to suggest the same things, keep that side of camper out of direct sun.
Blow air through.
Insulate the fridge cabinet better. The freezer is working fine, but the much bigger fridge cabinet is conducting off that cold air to the outside through the fridge walls and door.
Check the fridge door seal.
Keep the fridge full. I keep one or more jugs of water in there to help maintain the temp through the hottest part of the day and to delay how fast the fridge cools in hot weather.

I bought my camper used. Im sure there has been some damage due to off-level running, but the freezer freezes and only on hot days do I get above the "refrigerator" temp zone. I have not put in a fan yet or done anything

[WesternHorizon]

Edd505 wrote:
a 95 and it's still working?

The cooling unit has now been replaced twice since '95.

[Edd505]

Of all the replays I personally know Old-Biscuit know of what he speaks.

a 95 and it's still working? Buddy & I were in AZ January. He was in a 7 year old class A and came over when his fridge would not go below 39-40. Just under $2500 for a new fridge installed. Look inside the outside cover, see any yellow? If you do it's near dead.

[WesternHorizon]

Next I took the RV up to 9000 ft and the interior got up to 80F

And the fridge went to 40F during the day, on max cold. Given this, I would guess that once it gets to 90F later in the summer the fridge will go over 40F during the day.

So, next question. Should a different orifice be used for high altitude operation? Doesn't appear to be an option:

http://rvlife.com/altitudes-effects-on-rv/

Other ideas? Thanks.

[WesternHorizon]

Results of the cooling unit replacement...

Thermistor attached, on propane: About 40F
Thermistor attached, on AC: About 36F

Colder with the thermistor discconnected. Is the 2 year old thermistor bad?

The spec is 7 to 10K in ice water. Mine is 9K ohms. So the thermistor seems OK.

OK, is the flame low?

I was going to get a Camco but there are reports of very dangerous defects:

"I purchased this from Amazon to use on our toy hauler, it looked good and reviews seemed to be ok at the time. However I installed it and used it one time on a trip to the mountains. The second time we used the toy hauler I started smelling propane, a lot of propane. When I tracked the smell down I found that the regulator was leaking from the crimped seal on the outlet side of the regulator??? I'm glad I noticed this before a major problem occurred, ie EXPLOSION OR DEATH. I have used regulators for years on various things, however to have one fail like this after just a few months on the RV is scary!!"

Camco on Amazon

Camco early failure

I found this alternative. Made in USA and seems very good. We shall see.

Marshall Excelsior (MEGR-298) Excela-Flo Two-Stage Compact Regulator
https://www.amazon.com/gp/product/B00KTS0QDY/

Tank connection is reverse thread
Used yellow Teflon tape
Does not quite fit level, so turned it slightly
Checked for leaks with soapy water

Results at home (6000 ft) and 70F

After replacing propane regulator...

Setting on max cold
On propane: 36F, 8F freezer
On AC: 35F, 8F freezer

So, problem solved? Not yet.

[WesternHorizon]

April... cooling unit replacement!

Discovered this interesting company in Phoenix. They rebuild cooling units. Their website is very informative.

http://www.campfridge.com/

Very responsive, we quickly scheduled an installation.

Notes....

Matt W. has been doing this work for 18 years.

My RM2611 is NOT the original fridge! (My Tioga Montara is 1995: 24 years old)

Cooling unit degradation... "It's age" if it has been reasonably level

My freezer: Membrane or silicone grease was not installed so foam was completely adhered in the freezer area

(The replacement took three hours and a lot of work for an expert. I am very glad I did not attempt it.)

RM2611 is now out of production

No more parts, increasingly hard to rebuild the cooling units

Takes several hours to rebuild

If kept reasonably level, this rebuild may last 10 years

New units are narrower than my cabinet. There is not a direct replacement unit.

New units are not any more tolerant of off-level: "It's physics"

Measure level on floor of freezer not fridge. Fridge bottom is always warped.

Does not recommend compressor fridges for RV use. Compressor has a moving part (piston in cylinder) that is not suited to vibration and impact. Note: I have read that if your RV is mostly stationary, then a compressor fridge may be a good option.

Recommends a draft inducing fan at the top of the fridge vent

Does not recommend a fan at the bottom vent. This creates turbulence in the base area which can confuse the fridge into thinking that it needs to heat more. This can ruin the cooling unit.

Highly recommends using a smartphone and app to level. Very accurate. (I like the free Smart Level app.)

=== If currently living in RV and getting fridge replacement ===

Get a styrofoam ice chest and dry ice (Frys Supermarket). I got 4 lbs for two full 24 qt chests (one freezer, one fridge) and it was not enough.

If possible, remove contents 4-5 hrs before appointment and turn off the unit. A thawed unit will make disassembly easier but it is not critical.

The new unit will take 8 hrs to get cold. You will need to keep your food in the ice chest during this time.

====

I was pleased with this service. It is the kind of thing that becomes possible given the massive RV market in the Phoenix area. If you need a new cooling unit and can get to the area it is definitely an option to consider.

[WesternHorizon]

2oldman wrote:

WesternHorizon wrote:
AC on full blast all day. It was quite hot outside, 110F+, at 6500 feet elevation.

I sympathize. At 106F my rig is at 90 with one air. Very uncomfortable.. but my fridge always works great.

Update on this saga....

March: As suggested above: Orifice, burner tube, and flue cleaned. Not especially dirty and did not seem to make any difference.

Unplugged thermistor. Note: Burner goes out immediately. Must restart fridge, then it runs continuously when the thermistor is unplugged.

Overnight fridge would go down to 25 deg. But during the day (80F inside RV) still not staying under 40F. Reconnected thermistor to prevent freezing overnight.

[2oldman]

WesternHorizon wrote:
AC on full blast all day. It was quite hot outside, 110F+, at 6500 feet elevation.

I sympathize. At 106F my rig is at 90 with one air. Very uncomfortable.. but my fridge always works great.

[dougrainer]

WesternHorizon wrote:

dougrainer wrote:
His symptoms are classic for a partially blocked cooling unit. This happens over years when you ran the refer off level occasionally and you never notice the degradation of cooling until you need it to operate at 100 percent when it is warm/hot outside. Since it does the same on 120 and LP, he probably has a partially blocked cooling unit. Doug

Quite possible. I don't think the unit was boondocked much for the first 19 years. I boondock 95% of the time and have done about 400 nights in 5 years. That's close to 10000 hrs operation.

I am very careful to level but still cumulative damage could have occurred.

As you note, this would explain all symptoms.

If you want to test the refer for partially blocked---Put a cup of water inside the empty refer. Run the refer 24 hours on 120 by hooking up the 120 element direct to 120 volts. After 24 hours measure the temp of the water. If NOT below 32 to 34 degrees you have a partially blocked Cooling Unit. If Partially blocked, Doing any other things to get better cooling is a waste of time. If it is partially blocked no big deal, it still functions, just not at its best. Doug

[WesternHorizon]

dougrainer wrote:
His symptoms are classic for a partially blocked cooling unit. This happens over years when you ran the refer off level occasionally and you never notice the degradation of cooling until you need it to operate at 100 percent when it is warm/hot outside. Since it does the same on 120 and LP, he probably has a partially blocked cooling unit. Doug

Quite possible. I don't think the unit was boondocked much for the first 19 years. I boondock 95% of the time and have done about 400 nights in 5 years. That's close to 10000 hrs operation.

I am very careful to level but still cumulative damage could have occurred.

As you note, this would explain all symptoms.

[WesternHorizon]

garyemunson wrote:
Is the fridge in a slide? If so, it probably came with a factory installed muffin fan or two to help exhaust hot air out of the top of the fridge bay. They quit and you will have that problem. The ammonia charge never "gets low" in absorption fridges. A leak will empty it within a day and it will be dead. These replies pretty much cover every base...

1995, no slide.

A few months ago I removed the screens at the top of the condenser vent and also raised the cover two inches for better airflow.

Also installed a Bayite 200 CFM fan at the top to get ready for next summer's 110F outside temps.

But I have not yet programmed the Bayite digital controller -- so I have not been running the fan.

I think I'll try it on manual 😉

Agree, good coverage. Learned a lot. Will report on results.