Fridge efficiency advise

I searched, but am looking for more specific answers. 1 year lurker, 1st time poster here. :)

Wife and I are newly weds (2 yrs), no kids yet, and decided to dive into the RV lifestyle about a year ago. Came across a 1979 Fleetwood Prowler 23' TT and got it for a song as 3rd owners. Always been a Montana trailer. Previous owner was a EDPM roof installer, so he had put a new roof on it. Very slight water damage in the rear by the tub, but the new roof seems to have cured this. No leaks that we can find, I'm storing it in an indoor (heated) aircraft hangar when not in use, so hoping to get a few years out of it before upgrading. New Intellipower 9130 and I installed a charge wizard with it. Will be upgrading to new batteries this spring. Original Dometic RM66F fridge, original Presidential II Furnace, and original hot water heater. Replaced all bulbs with LEDs to reduce battery usage and installed a car stereo (have to have my Red Dirt Country!)

Fridge doesn't work on AC anymore, and I can't justify replacing the heater element on a 36 year old unit. So, everything except lights, water pump, stereo, and a 12v cig plug outlet (sometimes used for a fan) runs on propane. 2 - 30lb bottles gives us plenty of time for the primitive areas we visit here in Montana. Also have a Yamaha EF2000is for recharging.

On our last outing in August 2014, our fridge just wasn't keeping up. Started cooling it 2 days prior to leaving. Got down to about 38 inside. Filled it up (admittedly, probably too full for an absorption unit), and held steady at around 41. After 3 days at a primitive site, it was getting to around 49-51 degrees. WAY to warm. It was about 90 outside and with no AC, about 100 or so in the trailer during the day. Shortly after that trip, I winterized her and put her back inside for the winter.

Tonight, I decided to pull the fridge and have a look see and because I will be installing 4 computer case fans to help bring fresh air across the back. I also got a in the door fan for inside the unit.

Turns out, zero insulation around the fridge. About 5" on either side oft unit, and the plywood baffle across the top/rear of the fridge isn't flush with the top. I'm thinking I'm getting flue heat around the fridge.

The fridge is sitting upside down right now to "burp"... I don't hear gurgling when it runs, but I sure heard it when I flipped it. No yellow residue, no ammonia smell, so I don't think it's leaking.

So what say you? Will foam board with silver foil help? Should I do fiberglass batts instead? I am going to replace the baffle with a slightly larger one so it is flush. I also plan to insulate the top of the fridge with batts/board. If board, silver toward fridge, or away?

I plan to have two fans at the top of the exhaust vent, and another two about a foot lower. Each pair will be independently switchable.

So, do you think I'll see any improvement?

Also, if anyone has any info about my rig, Id love to have some. It's all been look, see, figure it out so far. I can't find any info on these trailers.

Thanks in advance!

dougrainer
Nomad
Jan 23, 2015
wareagle30 wrote:
I'll have to look at my service manual again. I don't recall there being an LP filter, but I am likely wrong.

We tested at the feed line, not a test port. Again, I'll have to look at the manual to find the test port. I'm guessing that it could be possible the fridge is seeing less than the 11" at the feed line? Looking at the back of the fridge, it looked like the feed line went into the valve, then into the tstat, then to burner.

And thanks for the advise - I'll pull the baffle and brush/blow out the flue tonight (time permitting).

So far in this thread, I've been told:

A) Increased air flow via fans might help
B) Not to replace the AC element
C) Replace the whole fridge with a residential model
D) Keep my current fridge and clean it
E) Adding insulation to the sides won't hurt, but more or less probably won't help

Between Chris and I, we have at least 70 years combined experience as RV techs, so, as to that filter, yes, you are wrong. Back then they had a white filter that looked like a cotton packing inside the LP valve. That filter, I do not believe is even mentioned in any of the Service manuals. The Heating element is about $65 on line. IF the refer functions correctly, then replacing the Heat Element is a good idea. Doug
wareagle30
Explorer
Jan 23, 2015
I'll have to look at my service manual again. I don't recall there being an LP filter, but I am likely wrong.

We tested at the feed line, not a test port. Again, I'll have to look at the manual to find the test port. I'm guessing that it could be possible the fridge is seeing less than the 11" at the feed line? Looking at the back of the fridge, it looked like the feed line went into the valve, then into the tstat, then to burner.

And thanks for the advise - I'll pull the baffle and brush/blow out the flue tonight (time permitting).

So far in this thread, I've been told:

A) Increased air flow via fans might help
B) Not to replace the AC element
C) Replace the whole fridge with a residential model
D) Keep my current fridge and clean it
E) Adding insulation to the sides won't hurt, but more or less probably won't help
Chris_Bryant
Explorer II
Jan 23, 2015
If you were testing at the test port on the refrigerator, that's good- there is an LP filter that becomes clogged over time with oil from the LP gas, but that's the first item inline (IIRC).
Do remove the baffle and run a brush down the flue and soak the orifice in alcohol- cannot hurt.
wareagle30
Explorer
Jan 23, 2015
I think a regular "dorm fridge" will be out of the question? (Looking for personal experiences given the explanation below...)

While I have a Yamaha EF2000iS generator, more often than not, the places we go don't have any elec hookups. More so, we usually setup base camp with the trailer, then go out on day long excursions. I don't want to leave the generator running (or out) while we're gone (I usually lock it up in the pickup). I haven't read much about how long a mini-fridge will stay cool without power, or how long/often I'd have to apply power from the gen to keep it sufficiently cool.

I've already got the computer fans and a couple switches. I've got some left over 1" and 3/4" foam board (with silver face) from a home insulation project. I figure I'll go ahead and insulate/install fans, reinstall burped fridge, and see how it goes.

Worst case scenario, the beer/water can go in the fridge and stay at 45-50, and we can put the perishables in the Yeti cooler for future trips. UNLESS, some of you can convince me that 30 mins or so of gen usage twice a day is sufficient to keep the fridge cool.

And yes Ed, I agree, any absorption replacement is out of the question. RM2510 is listed as the replacement, and they go for $675 at our dealer here in town, plus $75 freight. That'd be nearly half of what we paid for the trailer in the first place. And the 2510 isn't exactly a plug and play... I'd have to do some trimming on the opening. Not that I wouldn't with a residential fridge either (or fabricating trim pieces).

To the other poster, I was getting 11" water column at the valve when I tested it prior to winterizing. I'll clean the burner and jet too, but I've got a nice pretty blue flame right now. Probably about 1.5" tall.
dougrainer
Nomad
Jan 23, 2015
1. Install the heating element in the 2nd tube next to the original heat element. The cost of the 120 element is not that much
2. The INSULATION of the Cabinet in the RV is NOT a factor in how cold the refer gets. Doug
edbehnke
Explorer
Jan 23, 2015
wareagle, I've never heard of refrigs going bad in just 2-7 years...they should last a long time.

as for your refrig, i'd just say look at getting a regualar refrig, that is what several rvers i know have done. used rv refrigs are still running $700+.
Chris_Bryant
Explorer II
Jan 23, 2015
The first thing to do is check the LP pressure, clean the burner and flue and make sure the baffle is clean and in place- you need to make certain you are applying the correct amount of heat to the boiler, which is hard to do on LP gas (this is why testing is done with the electric element- easily measured application of heat).
This was a good model of refrigerator, in my opinion- well worth keeping for boondocking, as it require no 12 volt power, unlike new models.
ScottG
Nomad
Jan 23, 2015
Been through this myself. Save yourself some headache and bother and just replace the fridge. It's had it.
wareagle30
Explorer
Jan 23, 2015
Fishinghat wrote:
(snip)

Finally, I'm amazed a 1979 frig is still working. You're lucky.

I know! Especially after hearing about all kinds of folks that have theirs go bad after 2-7 years. I've read VERY few cases of someone reporting a 20+ year old fridge working.

Thanks for the input. How would I wire one inside the unit? How did you get the wires in? Mine doesn't have a light or 12v control board. She's OLD.
Fishinghat
Explorer II
Jan 23, 2015
I installed four computer fans on the inside of the lower vent to force cooling air past the coils and up and out the top vent. It seems to have helped quite a bit. The second thing I did was install a computer fan inside, wired to the light switch (before the switch so it stays on all the time). That has reduced the frost building up in the frig to near "0". Of course, the freezer still needs defrosting.

Some newer coaches have two larger fans at the top of the frig at the back on top of the top cooling coils and connected to thermal switches so they only run when the frig coils are quite warm. They appear to be a common feature as I've noticed these on new frig units for sale at RV stores.

Finally, I'm amazed a 1979 frig is still working. You're lucky.

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